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Avramov M, Thaivalappil A, Ludwig A, Miner L, Cullingham CI, Waddell L, Lapen DR. Relationships between water quality and mosquito presence and abundance: a systematic review and meta-analysis. JOURNAL OF MEDICAL ENTOMOLOGY 2024; 61:1-33. [PMID: 37832159 PMCID: PMC10784781 DOI: 10.1093/jme/tjad139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 08/31/2023] [Accepted: 09/18/2023] [Indexed: 10/15/2023]
Abstract
Mosquito-borne diseases (MBDs) are emerging in response to climate and land use changes. As mosquito (Diptera: Culicidae) habitat selection is often contingent on water availability for egg and larval development, studies have recognized water quality also influences larval habitats. However, underlying species-, genera-, and mosquito level preferences for water quality conditions are varied. This systematic review and meta-analysis aimed to identify, characterize, appraise, and synthesize available global data on the relationships between water quality and mosquito presence and abundance (MPA); with the goal to further our understanding of the geographic expansion of MBD risks. A systematic review was conducted to identify studies investigating the relationships between water quality properties and MPA. Where appropriate, random-effects meta-analyses were conducted to provide pooled estimates for the association between the most reported water quality properties and MPA. The most reported water quality parameters were pH (87%), nitrogen concentrations (56%), turbidity (56%), electrical conductivity (54%), dissolved oxygen (43%), phosphorus concentrations (30%), and alkalinity (10%). Overall, pH (P = 0.05), turbidity (P < 0.0001), electrical conductivity (P = 0.005), dissolved oxygen (P < 0.0001), nitrogen (P < 0.0001), and phosphorus (P < 0.0001) showed significantly positive pooled correlations with MPA, while alkalinity showed a nonsignificant null pooled correlation (P = 0.85). We observed high heterogeneity in most meta-analyses, and climate zonation was shown to influence the pooled estimates. Linkages between MPA and water quality properties will enhance our capacity to predict MBD risks under changing environmental and land use changes.
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Affiliation(s)
- Marc Avramov
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
- National Microbiology Laboratory Branch, Public Health Agency of Canada, 3200 rue Sicotte, C.P. 5000, St. Hyacinthe, QC J2S 2M2, Canada
- Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada
| | - Abhinand Thaivalappil
- Department of Population Medicine, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada
| | - Antoinette Ludwig
- National Microbiology Laboratory Branch, Public Health Agency of Canada, 3200 rue Sicotte, C.P. 5000, St. Hyacinthe, QC J2S 2M2, Canada
| | - Lauren Miner
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
| | - Catherine I Cullingham
- Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
| | - Lisa Waddell
- National Microbiology Laboratory Branch, Public Health Agency of Canada, 370 Speedvale Avenue West, Guelph, ON N1H 7M7, Canada
| | - David R Lapen
- Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, 960 Carling Avenue, Ottawa, ON K1A 0C6, Canada
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Javed N, López-Denman AJ, Paradkar PN, Bhatti A. EggCountAI: a convolutional neural network-based software for counting of Aedes aegypti mosquito eggs. Parasit Vectors 2023; 16:341. [PMID: 37779213 PMCID: PMC10544470 DOI: 10.1186/s13071-023-05956-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 08/28/2023] [Indexed: 10/03/2023] Open
Abstract
BACKGROUND Mosquito-borne diseases exert a huge impact on both animal and human populations, posing substantial health risks. The behavioural and fitness traits of mosquitoes, such as locomotion and fecundity, are crucial factors that influence the spread of diseases. In existing egg-counting tools, each image requires separate processing with adjustments to various parameters such as intensity threshold and egg area size. Furthermore, accuracy decreases significantly when dealing with clustered or overlapping eggs. To overcome these issues, we have developed EggCountAI, a Mask Region-based Convolutional Neural Network (RCNN)-based free automatic egg-counting tool for Aedes aegypti mosquitoes. METHODS The study design involves developing EggCountAI for counting mosquito eggs and comparing its performance with two commonly employed tools-ICount and MECVision-using 10 microscopic and 10 macroscopic images of eggs laid by females on a paper strip. The results were validated through manual egg counting on the strips using ImageJ software. Two different models were trained on macroscopic and microscopic images to enhance egg detection accuracy, achieving mean average precision, mean average recall, and F1-scores of 0.92, 0.90, and 0.91 for the microscopic model, and 0.91, 0.90, and 0.90 for the macroscopic model, respectively. EggCountAI automatically counts eggs in a folder containing egg strip images, offering adaptable filtration for handling impurities of varying sizes. RESULTS The results obtained from EggCountAI highlight its remarkable performance, achieving overall accuracy of 98.88% for micro images and 96.06% for macro images. EggCountAI significantly outperformed ICount and MECVision, with ICount achieving 81.71% accuracy for micro images and 82.22% for macro images, while MECVision achieved 68.01% accuracy for micro images and 51.71% for macro images. EggCountAI also excelled in other statistical parameters, with mean absolute error of 1.90 eggs for micro, 74.30 eggs for macro, and a strong correlation and R-squared value (0.99) for both micro and macro. The superior performance of EggCountAI was most evident when handling overlapping or clustered eggs. CONCLUSION Accurate detection and counting of mosquito eggs enables the identification of preferred egg-laying sites and facilitates optimal placement of oviposition traps, enhancing targeted vector control efforts and disease transmission prevention. In future research, the tool holds the potential to extend its application to monitor mosquito feeding preferences.
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Affiliation(s)
- Nouman Javed
- Institute for Intelligent Systems Research and Innovation, Deakin University, Geelong, VIC 3216 Australia
- CSIRO Health & Biosecurity, Australian Centre for Disease Preparedness, Geelong, VIC 3220 Australia
| | - Adam J. López-Denman
- CSIRO Health & Biosecurity, Australian Centre for Disease Preparedness, Geelong, VIC 3220 Australia
| | - Prasad N. Paradkar
- CSIRO Health & Biosecurity, Australian Centre for Disease Preparedness, Geelong, VIC 3220 Australia
| | - Asim Bhatti
- Institute for Intelligent Systems Research and Innovation, Deakin University, Geelong, VIC 3216 Australia
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Hasyim H, Dewi WC, Lestari RAF, Flora R, Novrikasari N, Liberty IA, Marini H, Elagali A, Herlinda S, Maharani FE. Risk factors of malaria transmission in mining workers in Muara Enim, South Sumatra, Indonesia. Sci Rep 2023; 13:14755. [PMID: 37679466 PMCID: PMC10484942 DOI: 10.1038/s41598-023-40418-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 08/09/2023] [Indexed: 09/09/2023] Open
Abstract
Eliminating malaria by 2030 is stated as goal three in the UN's Sustainable Development Goals (SDGs). However, malaria still remains a significant public health problem. This study aims to identify the factors determining malaria transmission in artisanal or small-scale miner (ASM) communities in three villages: Tanjung Agung, Tanjung Lalang, and Penyandingan, located in the Tanjung Enim District, Muara Enim, South Sumatra, Indonesia. Researchers conducted a cross-sectional study involving 92 participants from the study area. They used a logistic regression model to investigate the risk factors related to malaria occurrence. The multivariable analysis revealed that age (Adjusted Prevalence Ratio (APR) = 7.989 with 95% CI 1.724-37.002) and mosquito breeding (APR = 7.685 with 95% CI 1.502-39.309) were risk factors for malaria. On the other hand, higher education (APR = 0.104 with 95% CI 0.027-0.403), the use of mosquito repellent (APR = 0.138 with 95% CI 0.035-0.549), and the condition of house walls (APR = 0.145 with 95% CI 0.0414-0.511) were identified as protective factors. The current study highlights age and mosquito breeding sites as risk factors for malaria. Additionally, higher education, insect repellent use, and the condition of house walls are protective factors against malaria. Therefore, reducing risk factors and increasing protective measures through effective communication, information, and education are highly recommended to eliminate malaria in mining areas.
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Affiliation(s)
- Hamzah Hasyim
- Faculty of Public Health, Universitas Sriwijaya, Palembang, Indonesia.
- Faculty of Medicine, Institute for Occupational Medicine, Social Medicine and Environmental Medicine, Goethe University, Frankfurt Am Main, Germany.
| | - Wita Citra Dewi
- Faculty of Public Health, Universitas Sriwijaya, Palembang, Indonesia
| | | | - Rostika Flora
- Faculty of Public Health, Universitas Sriwijaya, Palembang, Indonesia
| | | | - Iche Andriyani Liberty
- Faculty of Medicine, Department of Public Health and Community Medicine, Universitas Sriwijaya, Palembang, Indonesia
| | - Heni Marini
- Faculty of Public Health, Universitas Sriwijaya, Palembang, Indonesia
| | - Ahmed Elagali
- School of Biological Sciences, The University of Western Australia, Perth, Australia
- Minderoo Foundation, Perth, Australia
| | - Siti Herlinda
- Faculty of Agriculture, Department of Plant Protection, Universitas Sriwijaya, Palembang, Indonesia
- Research Center for Sub-Optimal Lands (PUR-PLSO), Universitas Sriwijaya, Palembang, Indonesia
| | - Fadhilah Eka Maharani
- Faculty of Mathematics and Natural Sciences, Biology Department, Universitas Sriwijaya, Palembang, Indonesia
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Thierry DN, Djamouko-Djonkam L, Gisèle FD, Audrey MMP, Timoléon T, Serge Hubert ZT, Sinclair WC, Christophe AN. Assessment of the impact of the biological larvicide VectoMax G: Combination of Bacillus thuringiensis and Lysinibacillus sphaericus on non-target aquatic organisms in Yaoundé-Cameroon. Heliyon 2023; 9:e17723. [PMID: 37533979 PMCID: PMC10391952 DOI: 10.1016/j.heliyon.2023.e17723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 08/04/2023] Open
Abstract
There has been a renewed interest for larviciding during the recent decade. Although biological larvicides are considered not to be harmful to non-target organisms, there is still not sufficient data on the effect of new long-lasting larvicide formulations such as VectoMax G combining Bacillus thuringiensis israelensis and Lysinibacullus sphaericus on the environment especially on non-target organisms. The present study aimed to assess the possible influence of VectoMax G on the diversity and abundance of the aquatic fauna cohabiting with mosquito larvae in breeding habitats during a larviciding trial in the city of Yaoundé. Twelve districts of the city of Yaoundé divided into 6 intervention and 6 control sites were chosen for the study. In each district 4 semi-permanent or permanent aquatic habitats were followed. VectoMax G application was done once every two weeks during 6 months and aquatic organisms were collected 48 h after each treatment. All collected organisms were brought to the laboratory for identification. Physico-chemical parameters were recorded as well. A high diversity of the zooplankton was recorded in the intervention areas with 28 species collected against 14 species in the control areas. Cladocerans were the most represented group in both sites while Ostracods were found only in control sites. A total of 19 macro-invertebrates species were recorded in the control areas vs 16 species in the intervention areas. Gasteropods were the most represented groups of macro-invertebrates. Vertebrates such as larvivorous fishes and amphibians larvae were also found in approximately similar densities in both sites. The study indicated no significant influence of larviciding with VectoMax G on the diversity and abundance of the non-target aquatic fauna in the city of Yaoundé.
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Affiliation(s)
- Djepand-Ngognouak Thierry
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
- Faculty of Science, University of Yaoundé I, P.O. Box 337, Yaoundé, Cameroon
| | - Landre Djamouko-Djonkam
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
- Vector Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Foko Dadji Gisèle
- Laboratory of Zoology, Higher Teacher Training College, University of Yaoundé I, P.O. Box 47, Yaoundé, Cameroon
| | - Mayi Marie Paul Audrey
- Vector Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P.O. Box 067, Dschang, Cameroon
| | - Tchuinkam Timoléon
- Vector Borne Diseases Laboratory of the Applied Biology and Ecology Research Unit (VBID-URBEA), Department of Animal Biology, Faculty of Sciences of the University of Dschang, P.O. Box 067, Dschang, Cameroon
| | | | - Wondji Charles Sinclair
- Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L3 5QA, Liverpool, UK
- Centre for Research in Infectious Disease (CRID), Yaoundé, P.O. Box 13591, Cameroon
| | - Antonio-Nkondjio Christophe
- Malaria Research Laboratory, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale (OCEAC), P.O. Box 288, Yaoundé, Cameroon
- Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, L3 5QA, Liverpool, UK
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Laursen WJ, Budelli G, Tang R, Chang EC, Busby R, Shankar S, Gerber R, Greppi C, Albuquerque R, Garrity PA. Humidity sensors that alert mosquitoes to nearby hosts and egg-laying sites. Neuron 2023; 111:874-887.e8. [PMID: 36640768 PMCID: PMC10023463 DOI: 10.1016/j.neuron.2022.12.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/23/2022] [Accepted: 12/19/2022] [Indexed: 01/15/2023]
Abstract
To reproduce and to transmit disease, female mosquitoes must obtain blood meals and locate appropriate sites for egg laying (oviposition). While distinct sensory cues drive each behavior, humidity contributes to both. Here, we identify the mosquito's humidity sensors (hygrosensors). Using generalizable approaches designed to simplify genetic analysis in non-traditional model organisms, we demonstrate that the ionotropic receptor Ir93a mediates mosquito hygrosensation as well as thermosensation. We further show that Ir93a-dependent sensors drive human host proximity detection and blood-feeding behavior, consistent with the overlapping short-range heat and humidity gradients these targets generate. After blood feeding, gravid females require Ir93a to seek high humidity associated with preferred egg-laying sites. Reliance on Ir93a-dependent sensors to promote blood feeding and locate potential oviposition sites is shared between the malaria vector Anopheles gambiae and arbovirus vector Aedes aegypti. These Ir93a-dependent systems represent potential targets for efforts to control these human disease vectors.
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Affiliation(s)
- Willem J Laursen
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Gonzalo Budelli
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Ruocong Tang
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Elaine C Chang
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Rachel Busby
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Shruti Shankar
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Rachel Gerber
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Chloe Greppi
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Rebecca Albuquerque
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA
| | - Paul A Garrity
- Department of Biology and Volen Center for Complex Systems, Brandeis University, Waltham, MA 02453, USA.
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Olagunju EA. Is the presence of mosquitoes an indicator of poor environmental sanitation? JOURNAL OF WATER AND HEALTH 2023; 21:385-401. [PMID: 37338318 PMCID: wh_2023_280 DOI: 10.2166/wh.2023.280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
The World Health Organization has designated mosquitoes as the most lethal animal since they are known to spread pathogen-transmitting organisms. Understanding the many environmental elements that contribute to the spread of these vectors is one of the many strategies used to stop them. If there are mosquitoes around people, it may indicate that there is not an appropriate environmental sanitation program in place in the community or region. Environmental sanitation involves improving any elements of the physical environment that could have a negative impact on a person's survival, health, or physical environment. Keywords containing 'Aedes,' 'Culex,' 'Anopheles,' 'dengue,' 'malaria,' 'yellow fever,' 'Zika,' 'West Nile,' 'chikungunya,' 'resident,' 'environment,' 'sanitation,' 'mosquito control,' and 'breeding sites' of published articles on PubMed, Google Scholar, and ResearchGate were reviewed. It was discovered that the general population should be involved in mosquito and mosquito-borne disease control. Collaboration between health professionals and the general population is essential. The purpose of this paper is to increase public awareness of environmental health issues related to diseases carried by mosquitoes.
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Affiliation(s)
- Emmanuel Ajibola Olagunju
- Department of Crop and Environmental Protection, Faculty of Agricultural Sciences, Ladoke Akintola University of Technology, Ogbomoso, Nigeria E-mail:
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Katusi GC, Hermy MRG, Makayula SM, Ignell R, Govella NJ, Hill SR, Mnyone LL. Seasonal variation in abundance and blood meal sources of primary and secondary malaria vectors within Kilombero Valley, Southern Tanzania. Parasit Vectors 2022; 15:479. [PMID: 36539892 PMCID: PMC9768911 DOI: 10.1186/s13071-022-05586-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 08/20/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Existing control tools have significantly reduced malaria over the past two decades. However, progress has been stalled due to increased resistance in primary vectors and the increasing role of secondary vectors. This study aimed to investigate the impact of seasonal change on primary and secondary vector abundance and host preference. Understanding the impact of seasonal dynamics of primary and secondary vectors on disease transmission will inform effective strategies for vector management and control. METHODS Vector abundance was measured through longitudinal collection of mosquitoes, conducted monthly during the wet and dry seasons, in Sagamaganga, a village in the Kilombero Valley, Tanzania. Mosquitoes were collected indoors using CDC light traps and backpack aspirators, and outdoors using resting buckets baited with cattle urine. In addition, a direct measure of host preference was taken monthly using human- and cattle-baited mosquito electrocuting traps. A host census was conducted to provide an indirect measure of host preference together with monthly blood meal source analysis. All collected mosquitoes were assayed for Plasmodium sporozoites. RESULTS A total of 2828 anophelines were collected, of which 78.5% and 21.4%, were primary and secondary vectors, respectively. The abundance of the primary vectors, Anopheles arabiensis and Anopheles funestus, and of the secondary vectors varied seasonally. Indirect measures of host preference indicated that all vectors varied blood meal choice seasonally, with the direct measure confirming this for An. arabiensis. All anopheline mosquitoes tested negative for sporozoites. CONCLUSIONS At the study location, the abundance of both primary and secondary vectors changed seasonally. Indirect and direct measures of host preference demonstrated that An. arabiensis varied from being zoophilic to being more opportunistic during the wet and dry seasons. A similar trend was observed for the other vectors.
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Affiliation(s)
- Godfrey C. Katusi
- grid.414543.30000 0000 9144 642XDepartment of Environmental Health and Ecological Sciences, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O. Box 53, Morogoro, Tanzania ,grid.11887.370000 0000 9428 8105Department of Microbiology, Parasitology and Biotechnology, College of Veterinary Medicine and Biomedical Sciences, Sokoine University of Agriculture, P.O. Box 3019, Morogoro, Tanzania
| | - Marie R. G. Hermy
- grid.6341.00000 0000 8578 2742Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P.O. Box 190, 234 22 Lomma, Sweden
| | - Samwely M. Makayula
- grid.414543.30000 0000 9144 642XDepartment of Environmental Health and Ecological Sciences, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O. Box 53, Morogoro, Tanzania
| | - Rickard Ignell
- grid.6341.00000 0000 8578 2742Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P.O. Box 190, 234 22 Lomma, Sweden
| | - Nicodem J. Govella
- grid.414543.30000 0000 9144 642XDepartment of Environmental Health and Ecological Sciences, Ifakara Health Institute, Off Mlabani Passage, Ifakara, P.O. Box 53, Morogoro, Tanzania ,grid.451346.10000 0004 0468 1595School of Life Sciences and Bioengineering, Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania
| | - Sharon R. Hill
- grid.6341.00000 0000 8578 2742Disease Vector Group, Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, P.O. Box 190, 234 22 Lomma, Sweden
| | - Ladslaus L. Mnyone
- grid.11887.370000 0000 9428 8105Pest Management Centre, Sokoine University of Agriculture, P.O. Box 3110, Morogoro, Tanzania
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Katusiime M, Kabwama SN, Rukundo G, Kwesiga B, Bulage L, Rutazaana D, Ario AR, Harris J. Malaria outbreak facilitated by engagement in activities near swamps following increased rainfall and limited preventive measures: Oyam District, Uganda. PLOS GLOBAL PUBLIC HEALTH 2022; 2:e0000239. [PMID: 36962711 PMCID: PMC10021189 DOI: 10.1371/journal.pgph.0000239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 07/11/2022] [Indexed: 11/18/2022]
Abstract
In April 2019, the District Health Office of Oyam District, Uganda reported an upsurge in malaria cases exceeding expected epidemic thresholds, requiring outbreak response. We investigated the scope of outbreak and identified exposures for transmission to inform control measures. A confirmed case was a positive malaria rapid diagnostic test or malaria microscopy from 1 January-30 June 2019 in a resident or visitor of Acaba Sub-county, Oyam District. We reviewed medical records at health facilities to get case-patients. We conducted entomological and environmental assessments to determine vector density, and identify aquatic Anopheles habitats, conducted a case-control study to determine exposures associated with illness. Of 9,235 case-patients (AR = 33%), females (AR = 38%) were more affected than males (AR = 20%) (p<0.001). Children <18 years were more affected (AR = 37%) than adults (p<0.001). Among 83 case-patients and 83 asymptomatic controls, 65 (78%) case-patients and 33 (40%) controls engaged in activities <500m from a swamp (ORMH = 12, 95%CI 3.6-38); 18 (22%) case-patients and four (5%) controls lived <500m from rice irrigation sites (ORMH = 8.2, 95%CI 1.8-36); and 23 (28%) case-patients and four (5%) controls had water pools <100m from household for 3-5 days after rainfall (ORMH = 7.3, 95%CI 2.2-25). Twenty three (28%) case-patients and four (5%) controls did not sleep under bed nets the previous night (ORMH = 20, 95%CI 2.7-149); 68 (82%) case-patients and 43(52%) controls did not wear long-sleeved clothes during evenings (ORMH = 9.3, 95%CI 2.8-31). Indoor resting vector density was 4.7 female mosquitoes/household/night. All Anopheles aquatic habitats had Anopheles larvae. Weekly rainfall in 2019 was heavier (6.0±7.2mm) than same period in 2018 (1.8±1.8mm) (p = 0.006). This outbreak was facilitated by Anopheles aquatic habitats near homes created by human activities, following increased rainfall compounded by inadequate use of individual preventive measures. We recommended awareness on use of insecticide-treated bed nets, protective clothing, and avoiding creation of Anopheles aquatic habitats.
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Affiliation(s)
- Maureen Katusiime
- Uganda Public Health Fellowship Program, Ministry of Health, Kampala, Uganda
| | | | - Gerald Rukundo
- Uganda Public Health Fellowship Program, Ministry of Health, Kampala, Uganda
| | - Benon Kwesiga
- Uganda Public Health Fellowship Program, Ministry of Health, Kampala, Uganda
| | - Lilian Bulage
- Uganda Public Health Fellowship Program, Ministry of Health, Kampala, Uganda
| | - Damian Rutazaana
- National Malaria Control Division, Ministry of Health, Kampala, Uganda
| | - Alex Riolexus Ario
- Uganda Public Health Fellowship Program, Ministry of Health, Kampala, Uganda
- Ministry of Health, Kampala, Uganda
| | - Julie Harris
- US Centers for Disease Control and Prevention, Kampala, Uganda
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Sunish IP, Shriram AN, De A, Sugunan AP, Vijayachari P. Characterization of the anopheline vector breeding habitats: Implications for elimination of malaria in tribal inhabited Car Nicobar Island. Indian J Med Res 2022; 156:240-249. [PMID: 36629183 PMCID: PMC10057366 DOI: 10.4103/ijmr.ijmr_3189_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Background & objectives Malaria is an important public health problem in Andaman & Nicobar archipelago. Among the three districts, Nicobar is the most endemic district where API is >2. In this district, the malaria incidence in Car Nicobar Tehsil has declined steadily over the past 10 years. A renewed initiative to consolidate this gain is being made with the ultimate objective of achieving zero indigenous transmission of malaria in Car Nicobar. So, the present study undertook a close environmental monitoring of water bodies for assessing changes in the risk potential of mosquito vector breeding habitats which can augment the elimination programme. Methods The breeding habitats of anopheline mosquitoes were sampled in 16 areas of Car Nicobar Island for eight time periods during 2017-2020. Along with anophelines, various associated water parameters (n=60) were estimated, viz. physicochemical (n=13), and biological, which included culicine mosquito immatures, insect predators (n=5), phytoplanktons (n=31) and zooplanktons (n=10). Results In the 16 study sites, overall 1126 surface water stagnating bodies constituting 21 different habitat types were surveyed. Of these, 17 were positive for anopheline breeding. Water bodies from three villages were consistently found to be positive for anopheline breeding. However, early instars of anopheline larvae were more abundant compared to the late instars. Four anopheline species were recorded, including Anopheles sundaicus, A. barbirostris, A. insulaeflorum and A. subpictus, in which 48 per cent were A. sundaicus. Multivariable analysis indicated that anopheline density was significantly higher in permanent water bodies than in temporary habitats (P<0.05) (high risk of anophelines). The highest pH (≥8.2), dissolved solids (≥0.39) levels showed significantly (P<0.05) decreased larval densities (lower risk of breeding), adjusted with breeding sites and season. Nitrite levels increased (P=0.022) larval densities. Interpretation & conclusions The present study facilitated estimating the productive period of a larval habitat enabling target larval sources to reduce adult populations. Implementing larviciding strategy before monsoon season is presumably the most cost-effective strategy. The output can be utilized for environmental monitoring of mosquito breeding risk in other malaria endemic areas, particularly where medium/large water bodies are the predominant breeding sites for malaria vectors.
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Affiliation(s)
- I P Sunish
- ICMR-Regional Medical Research Centre, Port Blair, Andaman & Nicobar Islands
| | - A N Shriram
- ICMR-Regional Medical Research Centre, Port Blair, Andaman & Nicobar Islands; ICMR-Vector Control Research Centre, Puducherry, India
| | - Amitabha De
- Directorate of Health Services, Port Blair, Andaman & Nicobar Islands
| | - A P Sugunan
- ICMR-Regional Medical Research Centre, Port Blair, Andaman & Nicobar Islands
| | - P Vijayachari
- ICMR-Regional Medical Research Centre, Port Blair, Andaman & Nicobar Islands
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10
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Abstract
Given the stagnating progress in the fight against malaria, there is an urgent need for area-wide integrated vector management strategies to complement existing intra-domiciliary tools, i.e., insecticide-treated bednets and indoor residual spraying. In this study, we describe a pilot trial using drones for aerial application of Aquatain Mosquito Formulation (AMF), a monomolecular surface film with larvicidal activity, against the African malaria mosquito Anopheles arabiensis in an irrigated rice agro-ecosystem in Unguja island, Zanzibar, Tanzania. Nine rice paddies were randomly assigned to three treatments: (a) control (drone spraying with water only), (b) drone spraying with 1 mL/m2, or (c) drone spraying with 5 mL/m2 of AMF. Compared to control paddies, AMF treatments resulted in highly significant (p < 0.001) reductions in the number of larvae and pupae and >90% fewer emerging adults. The residual effect of AMF treatment lasted for a minimum of 5 weeks post-treatment, with reductions in larval densities reaching 94.7% in week 5 and 99.4% in week 4 for the 1 and 5 mL/m2 AMF treatments, respectively. These results merit a review of the WHO policy regarding larval source management (LSM), which primarily recommends its use in urban environments with ‘few, fixed, and findable’ breeding sites. Unmanned aerial vehicles (UAVs) can rapidly treat many permanent, temporary, or transient mosquito breeding sites over large areas at low cost, thereby significantly enhancing the role of LSM in contemporary malaria control and elimination efforts.
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11
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Viveros-Santos V, Hernández-Triana LM, Ibáñez-Bernal S, Ortega-Morales AI, Nikolova NI, Pairot P, Fooks AR, Casas-Martínez M. Integrated Approaches for the Identification of Mosquitoes (Diptera: Culicidae) from the Volcanoes of Central America Physiographic Subprovince of the State of Chiapas, Mexico. Vector Borne Zoonotic Dis 2022; 22:120-137. [PMID: 35175140 DOI: 10.1089/vbz.2021.0034] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nowadays, there is a lack of information on the mosquito's fauna and DNA barcoding sequence reference library from many areas in Mexico, including the Volcanoes of Central America physiographic subprovince in the state of Chiapas. Consequently, a survey was undertaken to delineate the mosquito (Diptera: Culicidae) fauna in this region across different seasons using different collecting techniques. All species were identified by morphology and DNA barcoding, and their ecological features were also defined. In total, 62 taxa were morphologically examined, 60 of these were successfully identified based on morphological characteristics, but two were unable to be identified at the species level. The genera Aedes, Anopheles, Culex, and Wyeomyia are the most diverse among mosquito genera collected and include several species of medical and veterinary importance. Ecological characteristics of the immature habitats indicated that they were grouped into four categories namely, (1) large water bodies at ground level, (2) small and shady phytotelmata (e.g., tree holes and bamboo internodes), (3) large phytotelmata (e.g., plant leaves and axis bromeliad), and (4) artificial containers. The cytochrome c oxidase subunit I (COI) DNA barcoding sequences successfully separated the majority of these species, although specific species showed >2% intraspecific genetic divergences.
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Affiliation(s)
- Vicente Viveros-Santos
- Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, México
| | | | | | - Aldo I Ortega-Morales
- Departamento de Parasitología, Universidad Autónoma Agraria Antonio Narro Unidad Laguna, Torreón, México
| | - Nadya I Nikolova
- Biodiversity Institute of Ontario, Universidad de Guelph, Ontario, Canadá
| | - Pramual Pairot
- Department of Biology, Faculty of Science, Mahasarakham University, Mahasarakham, Thailand
| | - Anthony R Fooks
- Virology Department, Animal and Plant Health Agency, Weybridge, United Kingdom
- Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Mauricio Casas-Martínez
- Centro Regional de Investigación en Salud Pública, Instituto Nacional de Salud Pública, Tapachula, México
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12
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Grass-like plants release general volatile cues attractive for gravid Anopheles gambiae sensu stricto mosquitoes. Parasit Vectors 2021; 14:552. [PMID: 34706760 PMCID: PMC8554987 DOI: 10.1186/s13071-021-04939-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 08/09/2021] [Indexed: 11/16/2022] Open
Abstract
Background Understanding the ecology and behaviour of disease vectors, including the olfactory cues used to orient and select hosts and egg-laying sites, are essential for the development of novel, insecticide-free control tools. Selected graminoid plants have been shown to release volatile chemicals attracting malaria vectors; however, whether the attraction is selective to individual plants or more general across genera and families is still unclear. Methods To contribute to the current evidence, we implemented bioassays in two-port airflow olfactometers and in large field cages with four live graminoid plant species commonly found associated with malaria vector breeding sites in western Kenya: Cyperus rotundus and C. exaltatus of the Cyperaceae family, and Panicum repens and Cynodon dactylon of the Poaceae family. Additionally, we tested one Poaceae species, Cenchrus setaceus, not usually associated with water. The volatile compounds released in the headspace of the plants were identified using gas chromatography/mass spectrometry. Results All five plants attracted gravid vectors, with the odds of a mosquito orienting towards the choice-chamber with the plant in an olfactometer being 2–5 times higher than when no plant was present. This attraction was maintained when tested with free-flying mosquitoes over a longer distance in large field cages, though at lower strength, with the odds of attracting a female 1.5–2.5 times higher when live plants were present than when only water was present in the trap. Cyperus rotundus, previously implicated in connection with an oviposition attractant, consistently elicited the strongest response from gravid vectors. Volatiles regularly detected were limonene, β-pinene, β-elemene and β-caryophyllene, among other common plant compounds previously described in association with odour-orientation of gravid and unfed malaria vectors. Conclusions The present study confirms that gravid Anopheles gambiae sensu stricto use chemical cues released from graminoid plants to orientate. These cues are released from a variety of graminoid plant species in both the Cyperaceae and Poaceae family. Given the general nature of these cues, it appears unlikely that they are exclusively used for the location of suitable oviposition sites. The utilization of these chemical cues for attract-and-kill trapping strategies must be explored under natural conditions to investigate their efficiency when in competition with complex interacting natural cues. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04939-4.
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13
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Dada N, Benedict AC, López F, Lol JC, Sheth M, Dzuris N, Padilla N, Lenhart A. Comprehensive characterization of internal and cuticle surface microbiota of laboratory-reared F 1 Anopheles albimanus originating from different sites. Malar J 2021; 20:414. [PMID: 34688298 PMCID: PMC8542342 DOI: 10.1186/s12936-021-03934-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 09/30/2021] [Indexed: 11/14/2022] Open
Abstract
Background Research on mosquito-microbe interactions may lead to new tools for mosquito and mosquito-borne disease control. To date, such research has largely utilized laboratory-reared mosquitoes that typically lack the microbial diversity of wild populations. A logical progression in this area involves working under controlled settings using field-collected mosquitoes or, in most cases, their progeny. Thus, an understanding of how laboratory colonization affects the assemblage of mosquito microbiota would aid in advancing mosquito microbiome studies and their applications beyond laboratory settings. Methods Using high throughput 16S rRNA amplicon sequencing, the internal and cuticle surface microbiota of F1 progeny of wild-caught adult Anopheles albimanus from four locations in Guatemala were characterized. A total of 132 late instar larvae and 135 2–5 day-old, non-blood-fed virgin adult females that were reared under identical laboratory conditions, were pooled (3 individuals/pool) and analysed. Results Results showed location-associated heterogeneity in both F1 larval internal (p = 0.001; pseudo-F = 9.53) and cuticle surface (p = 0.001; pseudo-F = 8.51) microbiota, and only F1 adult cuticle surface (p = 0.001; pseudo-F = 4.5) microbiota, with a more homogenous adult internal microbiota (p = 0.12; pseudo-F = 1.6) across collection sites. Overall, ASVs assigned to Leucobacter, Thorsellia, Chryseobacterium and uncharacterized Enterobacteriaceae, dominated F1 larval internal microbiota, while Acidovorax, Paucibacter, and uncharacterized Comamonadaceae, dominated the larval cuticle surface. F1 adults comprised a less diverse microbiota compared to larvae, with ASVs assigned to the genus Asaia dominating both internal and cuticle surface microbiota, and constituting at least 70% of taxa in each microbial niche. Conclusions These results suggest that location-specific heterogeneity in filed mosquito microbiota can be transferred to F1 progeny under normal laboratory conditions, but this may not last beyond the F1 larval stage without adjustments to maintain field-derived microbiota. These findings provide the first comprehensive characterization of laboratory-colonized F1An. albimanus progeny from field-derived mothers. This provides a background for studying how parentage and environmental conditions differentially or concomitantly affect mosquito microbiome composition, and how this can be exploited in advancing mosquito microbiome studies and their applications beyond laboratory settings. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03934-5.
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Affiliation(s)
- Nsa Dada
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, United States Centers for Diseases Control and Prevention, Atlanta, GA, USA. .,American Society for Microbiology, Washington, DC, USA. .,Tropical Infectious Diseases Research Center, University of Abomey-Calavi, Cotonou, Benin.
| | - Ana Cristina Benedict
- Grupo de Biología Y Control de Vectores, Centro de Estudios en Salud, Universidad del Valle de Guatemala, Guatemala City, Guatemala
| | - Francisco López
- Grupo de Biología Y Control de Vectores, Centro de Estudios en Salud, Universidad del Valle de Guatemala, Guatemala City, Guatemala
| | - Juan C Lol
- Grupo de Biología Y Control de Vectores, Centro de Estudios en Salud, Universidad del Valle de Guatemala, Guatemala City, Guatemala
| | - Mili Sheth
- Biotechnology Core Facility Branch, Division of Scientific Resources, National Center for Emerging & Zoonotic Infectious Diseases, United States Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Nicole Dzuris
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, United States Centers for Diseases Control and Prevention, Atlanta, GA, USA
| | - Norma Padilla
- Grupo de Biología Y Control de Vectores, Centro de Estudios en Salud, Universidad del Valle de Guatemala, Guatemala City, Guatemala
| | - Audrey Lenhart
- Entomology Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, United States Centers for Diseases Control and Prevention, Atlanta, GA, USA
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14
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Runge M, Mapua S, Nambunga I, Smith TA, Chitnis N, Okumu F, Pothin E. Evaluation of different deployment strategies for larviciding to control malaria: a simulation study. Malar J 2021; 20:324. [PMID: 34315473 PMCID: PMC8314573 DOI: 10.1186/s12936-021-03854-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Accepted: 07/16/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Larviciding against malaria vectors in Africa has been limited to indoor residual spraying and insecticide-treated nets, but is increasingly being considered by some countries as a complementary strategy. However, despite progress towards improved larvicides and new tools for mapping or treating mosquito-breeding sites, little is known about the optimal deployment strategies for larviciding in different transmission and seasonality settings. METHODS A malaria transmission model, OpenMalaria, was used to simulate varying larviciding strategies and their impact on host-seeking mosquito densities, entomological inoculation rate (EIR) and malaria prevalence. Variations in coverage, duration, frequency, and timing of larviciding were simulated for three transmission intensities and four transmission seasonality profiles. Malaria transmission was assumed to follow rainfall with a lag of one month. Theoretical sub-Saharan African settings with Anopheles gambiae as the dominant vector were chosen to explore impact. Relative reduction compared to no larviciding was predicted for each indicator during the simulated larviciding period. RESULTS Larviciding immediately reduced the predicted host-seeking mosquito densities and EIRs to a maximum that approached or exceeded the simulated coverage. Reduction in prevalence was delayed by approximately one month. The relative reduction in prevalence was up to four times higher at low than high transmission. Reducing larviciding frequency (i.e., from every 5 to 10 days) resulted in substantial loss in effectiveness (54, 45 and 53% loss of impact for host-seeking mosquito densities, EIR and prevalence, respectively). In seasonal settings the most effective timing of larviciding was during or at the beginning of the rainy season and least impactful during the dry season, assuming larviciding deployment for four months. CONCLUSION The results highlight the critical role of deployment strategies on the impact of larviciding. Overall, larviciding would be more effective in settings with low and seasonal transmission, and at the beginning and during the peak densities of the target species populations. For maximum impact, implementers should consider the practical ranges of coverage, duration, frequency, and timing of larviciding in their respective contexts. More operational data and improved calibration would enable models to become a practical tool to support malaria control programmes in developing larviciding strategies that account for the diversity of contexts.
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Affiliation(s)
- Manuela Runge
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Salum Mapua
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Ismail Nambunga
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Fredros Okumu
- Environmental Health and Ecological Sciences Department, Ifakara Health Institute, Ifakara, Tanzania
| | - Emilie Pothin
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Clinton Health Access Initiative, Boston, USA
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15
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Girard M, Martin E, Vallon L, Raquin V, Bellet C, Rozier Y, Desouhant E, Hay AE, Luis P, Valiente Moro C, Minard G. Microorganisms Associated with Mosquito Oviposition Sites: Implications for Habitat Selection and Insect Life Histories. Microorganisms 2021; 9:1589. [PMID: 34442667 PMCID: PMC8401263 DOI: 10.3390/microorganisms9081589] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 07/08/2021] [Accepted: 07/21/2021] [Indexed: 01/03/2023] Open
Abstract
Mosquitoes are considered one of the most important threats worldwide due to their ability to vector pathogens. They are responsible for the transmission of major pathogens such as malaria, dengue, zika, or chikungunya. Due to the lack of treatments or prophylaxis against many of the transmitted pathogens and an increasing prevalence of mosquito resistance to insecticides and drugs available, alternative strategies are now being explored. Some of these involve the use of microorganisms as promising agent to limit the fitness of mosquitoes, attract or repel them, and decrease the replication and transmission of pathogenic agents. In recent years, the importance of microorganisms colonizing the habitat of mosquitoes has particularly been investigated since they appeared to play major roles in their development and diseases transmission. In this issue, we will synthesize researches investigating how microorganisms present within water habitats may influence breeding site selection and oviposition strategies of gravid mosquito females. We will also highlight the impact of such microbes on the fate of females' progeny during their immature stages with a specific focus on egg hatching, development rate, and larvae or pupae survival.
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Affiliation(s)
- Maxime Girard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Edwige Martin
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Laurent Vallon
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Vincent Raquin
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Christophe Bellet
- Entente Interdépartementale Rhône-Alpes pour la Démoustication, F-73310 Chindrieux, France; (C.B.); (Y.R.)
| | - Yves Rozier
- Entente Interdépartementale Rhône-Alpes pour la Démoustication, F-73310 Chindrieux, France; (C.B.); (Y.R.)
| | - Emmanuel Desouhant
- Univ. Lyon, Université Claude Bernard Lyon 1, Laboratoire de Biométrie et de Biologie Evolutive, UMR CNRS 5558, VetAgro Sup, F-69622 Villeurbanne, France;
| | - Anne-Emmanuelle Hay
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Patricia Luis
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Claire Valiente Moro
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
| | - Guillaume Minard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, INRAE, VetAgro Sup, UMR Ecologie Microbienne, F-69622 Villeurbanne, France; (M.G.); (E.M.); (L.V.); (V.R.); (A.-E.H.); (P.L.); (C.V.M.)
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16
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Morris AL, Ghani A, Ferguson N. Fine-scale estimation of key life-history parameters of malaria vectors: implications for next-generation vector control technologies. Parasit Vectors 2021; 14:311. [PMID: 34103094 PMCID: PMC8188720 DOI: 10.1186/s13071-021-04789-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 05/11/2021] [Indexed: 11/12/2022] Open
Abstract
Background Mosquito control has the potential to significantly reduce malaria burden on a region, but to influence public health policy must also show cost-effectiveness. Gaps in our knowledge of mosquito population dynamics mean that mathematical modelling of vector control interventions have typically made simplifying assumptions about key aspects of mosquito ecology. Often, these assumptions can distort the predicted efficacy of vector control, particularly next-generation tools such as gene drive, which are highly sensitive to local mosquito dynamics. Methods We developed a discrete-time stochastic mathematical model of mosquito population dynamics to explore the fine-scale behaviour of egg-laying and larval density dependence on parameter estimation. The model was fitted to longitudinal mosquito population count data using particle Markov chain Monte Carlo methods. Results By modelling fine-scale behaviour of egg-laying under varying density dependence scenarios we refine our life history parameter estimates, and in particular we see how model assumptions affect population growth rate (Rm), a crucial determinate of vector control efficacy. Conclusions Subsequent application of these new parameter estimates to gene drive models show how the understanding and implementation of fine-scale processes, when deriving parameter estimates, may have a profound influence on successful vector control. The consequences of this may be of crucial interest when devising future public health policy. Graphic abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04789-0.
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Affiliation(s)
- Aaron L Morris
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK.
| | - Azra Ghani
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Neil Ferguson
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College London, Norfolk Place, London, W2 1PG, UK
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17
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Chen D, Shevade V, Baer A, He J, Hoffman-Hall A, Ying Q, Li Y, Loboda TV. A Disease Control-Oriented Land Cover Land Use Map for Myanmar. DATA 2021; 6:63. [PMID: 34504894 PMCID: PMC8425379 DOI: 10.3390/data6060063] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Malaria is a serious infectious disease that leads to massive casualties globally. Myanmar is a key battleground for the global fight against malaria because it is where the emergence of drug-resistant malaria parasites has been documented. Controlling the spread of malaria in Myanmar thus carries global significance, because the failure to do so would lead to devastating consequences in vast areas where malaria is prevalent in tropical/subtropical regions around the world. Thanks to its wide and consistent spatial coverage, remote sensing has become increasingly used in the public health domain. Specifically, remote sensing-based land cover/land use (LCLU) maps present a powerful tool that provides critical information on population distribution and on the potential human-vector interactions interfaces on a large spatial scale. Here, we present a 30-meter LCLU map that was created specifically for the malaria control and eradication efforts in Myanmar. This bottom-up approach can be modified and customized to other vector-borne infectious diseases in Myanmar or other Southeastern Asian countries.
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Affiliation(s)
- Dong Chen
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
| | - Varada Shevade
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
| | - Allison Baer
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
| | - Jiaying He
- Department of Earth System Science, Tsinghua University, Beijing 100084, China
| | - Amanda Hoffman-Hall
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
| | - Qing Ying
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
- Department of Geosciences, Texas Tech University, Lubbock, TX 79409, USA
| | - Yao Li
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
| | - Tatiana V. Loboda
- Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USA
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18
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Lupenza ET, Kihonda J, Limwagu AJ, Ngowo HS, Sumaye RD, Lwetoijera DW. Using pastoralist community knowledge to locate and treat dry-season mosquito breeding habitats with pyriproxyfen to control Anopheles gambiae s.l. and Anopheles funestus s.l. in rural Tanzania. Parasitol Res 2021; 120:1193-1202. [PMID: 33409645 DOI: 10.1007/s00436-020-07040-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Accepted: 12/25/2020] [Indexed: 10/22/2022]
Abstract
Fundamentally, larviciding with pyriproxyfen (PPF) has potential to complement Long Lasting Insecticide Nets (LLINs) and indoor residual sprays (IRS) in settings where resistance to pyrethroids and residual malaria transmission exist. In this study, we evaluated the field effectiveness of larviciding using PPF to reduce dry season productivity of mosquito breeding habitats that were located by pastoralists within the study area. Using pastoralist knowledge, dry season breeding habitats in Mofu village rural Tanzania were located and monitored for larval productivity for a period of 8 months before PPF intervention. During the intervention, six out of twelve breeding habitats were treated with Sumilarv 0.5G PPF granules. The impact of deposited PPF was monitored by recording emergence inhibition of larvae collected from treated habitats compared to the appropriate control group for a period of three months and half post-intervention. During baseline, the average proportion (+SD) of adult emerged was similar between two clusters, with (0.89 + 0.22) for the control cluster and (0.93 + 0.16) for the treatment cluster of breeding habitats. Following treatment with PPF, the average proportion (+SD) of adult emerged in the treated breeding habitats was significantly low (0.096 + 0.22) compared to adults that emerged from larvae in the untreated habitats (0.99 + 0.22) (p < 0.0001). Of all emerged adults, approximately 94% were An. gambiae s.l. and the remaining 6% were An. funestus s.l. This is the first study demonstrating the usefulness of engaging pastoralist community to locate and identify hard to find mosquito breeding habitats. Reduced productivity of the targeted habitats with PPF offers prospect of implementing PPF larviciding in dry season when habitats are few and permanent to control mosquito population in rural settings.
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Affiliation(s)
- Eliza T Lupenza
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Japhet Kihonda
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Alex J Limwagu
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Halfan S Ngowo
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Robert D Sumaye
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania
| | - Dickson W Lwetoijera
- Environmental Health and Ecological Science Department, Ifakara Health Institute, P.O. Box 53, Ifakara, Tanzania. .,School of Life Science and Bioengineering, Nelson Mandela African Institution of Science & Technology, Arusha, Tanzania.
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19
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Mwingira V, Mboera LEG, Dicke M, Takken W. Exploiting the chemical ecology of mosquito oviposition behavior in mosquito surveillance and control: a review. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2020; 45:155-179. [PMID: 33207066 DOI: 10.1111/jvec.12387] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Vector control is an important component of the interventions aimed at mosquito-borne disease control. Current and future mosquito control strategies are likely to rely largely on the understanding of the behavior of the vector, by exploiting mosquito biology and behavior, while using cost-effective, carefully timed larvicidal and high-impact, low-volume adulticidal applications. Here we review the knowledge on the ecology of mosquito oviposition behavior with emphasis on the potential role of infochemicals in surveillance and control of mosquito-borne diseases. A search of PubMed, Embase, Web of Science, Global Health Archive, and Google Scholar databases was conducted using the keywords mosquito, infochemical, pheromone, kairomone, allomone, synomone, apneumone, attractant, host-seeking, and oviposition. Articles in English from 1974 to 2019 were reviewed to gain comprehensive understanding of current knowledge on infochemicals in mosquito resource-searching behavior. Oviposition of many mosquito species is mediated by infochemicals that comprise pheromones, kairomones, synomones, allomones, and apneumones. The novel putative infochemicals that mediate oviposition in the mosquito subfamilies Anophelinae and Culicinae were identified. The role of infochemicals in surveillance and control of these and other mosquito tribes is discussed with respect to origin of the chemical cues and how these affect gravid mosquitoes. Oviposition attractants and deterrents can potentially be used for manipulation of mosquito behavior by making protected resources unsuitable for mosquitoes (push) while luring them towards attractive sources (pull). In this review, strategies of targeting breeding sites with environmentally friendly larvicides with the aim to develop appropriate trap-and-kill techniques are discussed.
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Affiliation(s)
- Victor Mwingira
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
- National Institute for Medical Research, Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, P.O. Box 3297 Chuo Kikuu, Morogoro, Tanzania
| | - Marcel Dicke
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University and Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands
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Bokore GE, Ouma P, Onyango PO, Bukhari T, Fillinger U. A cross-sectional observational study investigating the association between sedges (swamp grasses, Cyperaceae) and the prevalence of immature malaria vectors in aquatic habitats along the shore of Lake Victoria, western Kenya. F1000Res 2020; 9:1032. [PMID: 33093949 PMCID: PMC7551511 DOI: 10.12688/f1000research.25673.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/24/2020] [Indexed: 12/01/2022] Open
Abstract
Background: Strategies that involve manipulations of the odour-orientation of gravid malaria vectors could lead to novel attract-and-kill interventions. Recent work has highlighted the potential involvement of graminoid plants in luring vectors to oviposition sites. This study aimed to analyse the association between water-indicating graminoid plants (Cyperaceae, sedges), other abiotic and biotic factors and the presence and abundance of early instar
Anopheles larvae in aquatic habitats as a proxy indicator for oviposition. Methods: A cross-sectional survey of 110 aquatic habitats along the shores of Lake Victoria was done during the rainy season. Habitats were sampled for mosquito larvae using the sweep-net method and habitat characteristics recorded. Results:
Anopheles arabiensis was the dominant species identified from aquatic habitats. Larvae of the secondary malaria vectors such as
Anopheles coustani, An. rufipes and
An. maculipalpis were found only in habitats covered with graminoids, whereas
An. arabiensis, An. ziemanni and
An. pharoensis were found in both habitats with and without graminoid plants. The hypothesis that sedges might be positively associated with the presence and abundance of early instar
Anopheles larvae could not be confirmed. The dominant graminoid plants in the habitats were
Panicum repens,
Cynodon dactylon in the Poaceae family and
Cyperus rotundus in the Cyperaceae family. All of these habitats supported abundant immature vector populations. The presence of early instar larvae was significantly and positively associated with swamp habitat types (OR=22, 95% CI=6-86, P<0.001) and abundance of late
Anopheles larvae (OR=359, CI=33-3941, P<0.001), and negatively associated with the presence of tadpoles (OR=0.1, CI=0.0.01-0.5, P=0.008). Conclusions: Early instar malaria vectors were abundant in habitats densely vegetated with graminoid plants in the study area but no specific preference could be detected for any species or family. In search for oviposition cues, it might be useful to screen for chemical volatiles released from all dominant plant species.
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Affiliation(s)
- Getachew E Bokore
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya.,School of Physical and Biological Sciences, Department of Zoology, Maseno University, P.O. Box 333 - 40105, Maseno, Kenya.,Public Health Entomology Team, Ethiopian Public Health Institute, P.O. Box 1242, Addis Ababa, Ethiopia
| | - Paul Ouma
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya
| | - Patrick O Onyango
- School of Physical and Biological Sciences, Department of Zoology, Maseno University, P.O. Box 333 - 40105, Maseno, Kenya
| | - Tullu Bukhari
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya.,School of Physical and Biological Sciences, Department of Zoology, Maseno University, P.O. Box 333 - 40105, Maseno, Kenya
| | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology (icipe), P.O. Box 30772-00100, Nairobi, Kenya
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Gowelo S, Chirombo J, Koenraadt CJM, Mzilahowa T, van den Berg H, Takken W, McCann RS. Characterisation of anopheline larval habitats in southern Malawi. Acta Trop 2020; 210:105558. [PMID: 32485166 PMCID: PMC7673143 DOI: 10.1016/j.actatropica.2020.105558] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Revised: 05/22/2020] [Accepted: 05/22/2020] [Indexed: 10/24/2022]
Abstract
INTRODUCTION Increasing the knowledgebase of anopheline larval ecology could enable targeted deployment of malaria control efforts and consequently reduce costs of implementation. In Malawi, there exists a knowledge gap in anopheline larval ecology and, therefore, basis for targeted deployment of larval source management (LSM) for malaria control, specifically larvicides. We set out to characterize anopheline larval habitats in the Majete area of Malawi on the basis of habitat ecology and anopheline larval productivity to create a basis for larval control initiatives in the country. METHODS Longitudinal surveys were conducted in randomly selected larval habitats over a period of fifteen months in Chikwawa district, southern Malawi. Biotic and abiotic parameters of the habitats were modelled to determine their effect on the occurrence and densities of anopheline larvae. RESULTS Seventy aquatic habitats were individually visited between 1-7 times over the study period. A total of 5,123 immature mosquitoes (3,359 anophelines, 1,497 culicines and 267 pupae) were collected. Anopheline and culicine larvae were observed in sympatry in aquatic habitats. Of the nine habitat types followed, dams, swamps, ponds, borehole runoffs and drainage channels were the five most productive habitat types for anopheline mosquitoes. Anopheline densities were higher in aquatic habitats with bare soil making up part of the surrounding land cover (p<0.01) and in aquatic habitats with culicine larvae (p<0.01) than in those surrounded by vegetation and not occupied by culicine larvae. Anopheline densities were significantly lower in highly turbid habitats than in clearer habitats (p<0.01). Presence of predators in the aquatic habitats significantly reduced the probability of anopheline larvae being present (p=0.04). CONCLUSIONS Anopheline larval habitats are widespread in the study area. Presence of bare soil, culicine larvae, predators and the level of turbidity of water are the main determinants of anopheline larval densities in aquatic habitats in Majete, Malawi. While the most productive aquatic habitats should be prioritised, for the most effective control of vectors in the area all available aquatic habitats should be targeted, even those that are not characterized by the identified predictors. Further research is needed to determine whether targeted LSM would be cost-effective when habitat characterisation is included in cost analyses and to establish what methods would make the characterisation of habitats easier.
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Affiliation(s)
- Steven Gowelo
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands; Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi
| | - James Chirombo
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, Blantyre, Malawi
| | | | | | - Henk van den Berg
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands.
| | - Robert S McCann
- Laboratory of Entomology, Wageningen University & Research, Wageningen, The Netherlands; Training and Research Unit of Excellence, School of Public Health, College of Medicine, Blantyre, Malawi; Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
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Alkhayat FA, Ahmad AH, Rahim J, Dieng H, Ismail BA, Imran M, Sheikh UAA, Shahzad MS, Abid AD, Munawar K. Charaterization of mosquito larval habitats in Qatar. Saudi J Biol Sci 2020; 27:2358-2365. [PMID: 32884417 PMCID: PMC7451668 DOI: 10.1016/j.sjbs.2020.07.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2020] [Revised: 06/24/2020] [Accepted: 07/05/2020] [Indexed: 01/21/2023] Open
Abstract
Mosquito borne diseases have remained a grave threat to human health and are posing a significant burden on health authorities around the globe. The understanding and insight of mosquito breeding habitats features is crucial for their effective management. Comprehensive larval surveys were carried out at 14 sites in Qatar. A total of 443 aquatic habitats were examined, among these 130 were found positive with Culex pipiens, Cx. quinquefasciatus, Cx. mattinglyi, Ochlerotatus dorsalis, Oc. caspius and Anopheles stephensi. The majority of positive breeding habitats were recorded in urban areas (67.6%), followed by livestock (13.8%), and least were in agriculture (10.7%). An. stephensi larvae were positively correlated with Cx. pipien, Cx. quinquefasciatus, and negatively with water salinity. Large and shaded habitats were the most preferred by An. stephensi. In addition, Cx. pipiens was positively associated with the turbidity and pH, and was negatively associated with vegetation and habitat size. A negative association of Cx. quinquefasciatus with dissolved oxygen, water temperature, and salinity, while positive with habitat surface area was observed. Oc. dorsalis was negatively correlated with pH, water temperature, depth, and habitat surface area, whereas salinity water was more preferable site for females to lay their eggs. These results demonstrate that environmental factors play a significant role in preference of both anopheline and culicine for oviposition, while their effective management must be developed as the most viable tool to minimize mosquito borne diseases.
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Affiliation(s)
- Fatima Abdulla Alkhayat
- School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia.,Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
| | - Abu H Ahmad
- School of Biological Sciences, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
| | - Junaid Rahim
- Department of Entomology, Faculty of Agriculture, University of Poonch Rawalakot, Poonch, Azad Jammu and Kashmir, Pakistan
| | - Hamady Dieng
- Mosquito Research and Control Unit, 99, Red Gate Road, George Town, Grand Cayman KY1-1106, Cayman Islands
| | | | - Muhammad Imran
- Department of Entomology, Faculty of Agriculture, University of Poonch Rawalakot, Poonch, Azad Jammu and Kashmir, Pakistan
| | - Umer Ayyaz Aslam Sheikh
- Department of Entomology, Faculty of Agriculture, University of Poonch Rawalakot, Poonch, Azad Jammu and Kashmir, Pakistan
| | - Muhmmad Sohail Shahzad
- Department of Plant Protection (Karachi), Ministry of National Food Security and Research, Pakistan
| | - Allah Ditta Abid
- Department of Plant Protection (Karachi), Ministry of National Food Security and Research, Pakistan
| | - Kashif Munawar
- Plant Protection Department, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Saudi Arabia
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South J, Botha TL, Wolmarans NJ, Wepener V, Weyl OLF. Playing with food: Detection of prey injury cues stimulates increased functional foraging traits in Xenopus laevis. AFRICAN ZOOLOGY 2020. [DOI: 10.1080/15627020.2020.1723439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Josie South
- DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa
| | - Tarryn L Botha
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Nico J Wolmarans
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
- Department of Biology, University of Antwerp, Antwerp, Belgium
| | - Victor Wepener
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
| | - Olaf LF Weyl
- DST/NRF Research Chair in Inland Fisheries and Freshwater Ecology, South African Institute for Aquatic Biodiversity (SAIAB), Grahamstown, South Africa
- Unit for Environmental Sciences and Management, North-West University, Potchefstroom, South Africa
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Anopheles larval species composition and characterization of breeding habitats in two localities in the Ghibe River Basin, southwestern Ethiopia. Malar J 2020; 19:65. [PMID: 32046734 PMCID: PMC7014609 DOI: 10.1186/s12936-020-3145-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 01/30/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Documentation of the species composition of Anopheles mosquitoes and characterization of larval breeding sites is of major importance for the implementation of larval control as part of malaria vector control interventions in Ethiopia. The aims of this study were to determine the Anopheles larval species composition, larval density, available habitat types and the effects of related environmental and physico-chemical parameters of habitats in the Ghibe River basin of southwestern Ethiopia. METHODS Anopheles larvae were sampled from November 2014 to October 2016 on a monthly basis and 3rd and 4th instars were identified microscopically to species. The larval habitats were characterized based on habitat perimeter, water depth, intensity of light, water current, water temperature, water pH, water turbidity, distance to the nearest house, vegetation coverage, permanence of the habitat, surface debris coverage, emergent plant coverage, habitat type and substrate type. RESULTS In total, 9277 larvae of Anopheles mosquitoes and 494 pupae were sampled from borrow pits, hoof prints, rain pools, pools at river edges, pools in drying river beds, rock pools, tire tracks and swamps. Anopheles larval density was highest in pools in drying river beds (35.2 larvae per dip) and lowest in swamps (2.1 larvae per dip) at Darge, but highest in rain pools (11.9 larvae per dip), borrow pits (11.2 larvae per dip) and pools at river edges (7.9 larvae per dip), and lowest in swamps (0.5 larvae per dip) at Ghibe. A total of 3485 late instar Anopheles mosquito larvae were morphologically identified. Anopheles gambiae sensu lato was the primary Anopheles mosquito found in all larval habitats except in swamps. Temperature at the time of sampling and emergent vegetation, were the most important variables for Anopheles mosquito larval density. Anopheles gambiae density was significantly associated with habitats that had smaller perimeters, were sunlit, had low vegetation cover, and a lack of emergent plants. Generally, Anopheles mosquito larval density was not significantly associated with water pH, water temperature, water turbidity, algal content, and larval habitat depth. CONCLUSION Different species of Anopheles larvae were identified including An. gambiae s.l., the main malaria vector in Ethiopia. Anopheles gambiae s.l. is the most abundant species that bred in most of the larval habitat types identified in the study area. The density of this species was high in sunlit habitat, absence of emergent plants, lack of vegetation near habitat and habitats closer to human habitation. Rainfall plays a great role in determining the availability of breeding habitats. The presence of rain enable to create some of the habitat types, but alter the habitats formed at the edge of the rivers due to over flooding. Controlling the occurrence of mosquito larvae through larval source management during the dry season, targeting the pools in drying river bed and pools formed at the edge of the rivers as the water receded can be very crucial to interrupt the re-emergence of malaria vectors on the onset of rainy season.
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Saddler A, Kreppel KS, Chitnis N, Smith TA, Denz A, Moore JD, Tambwe MM, Moore SJ. The development and evaluation of a self-marking unit to estimate malaria vector survival and dispersal distance. Malar J 2019; 18:441. [PMID: 31870365 PMCID: PMC6929409 DOI: 10.1186/s12936-019-3077-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 12/14/2019] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND A clear understanding of mosquito biology is fundamental to the control efforts of mosquito-borne diseases such as malaria. Mosquito mark-release-recapture (MMRR) experiments are a popular method of measuring the survival and dispersal of disease vectors; however, examples with African malaria vectors are limited. Ethical and technical difficulties involved in carrying out MMRR studies may have held back research in this area and, therefore, a device that marks mosquitoes as they emerge from breeding sites was developed and evaluated to overcome the problems of MMRR. METHODS A modified self-marking unit that marks mosquitoes with fluorescent pigment as they emerge from their breeding site was developed based on a previous design for Culex mosquitoes. The self-marking unit was first evaluated under semi-field conditions with laboratory-reared Anopheles arabiensis to determine the marking success and impact on mosquito survival. Subsequently, a field evaluation of MMRR was conducted in Yombo village, Tanzania, to examine the feasibility of the system. RESULTS During the semi-field evaluation the self-marking units successfully marked 86% of emerging mosquitoes and there was no effect of fluorescent marker on mosquito survival. The unit successfully marked wild male and female Anopheles gambiae sensu lato (s.l.) in sufficiently large numbers to justify its use in MMRR studies. The estimated daily survival probability of An. gambiae s.l. was 0.87 (95% CI 0.69-1.10) and mean dispersal distance was 579 m (95% CI 521-636 m). CONCLUSIONS This study demonstrates the successful use of a self-marking device in an MMRR study with African malaria vectors. This method may be useful in investigating population structure and dispersal of mosquitoes for deployment and evaluation of future vector control tools, such as gene drive, and to better parameterize mathematical models.
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Affiliation(s)
- Adam Saddler
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania.
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland.
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland.
| | - Katharina S Kreppel
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Nelson Mandela African Institution of Science and Technology, P.O. Box 447, Tengeru, Tanzania
| | - Nakul Chitnis
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Thomas A Smith
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Adrian Denz
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Jason D Moore
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Mgeni M Tambwe
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
| | - Sarah J Moore
- Ifakara Health Institute, Environmental Health and Ecological Sciences, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical & Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland
- University of Basel, Petersplatz 1, 4001, Basel, Switzerland
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Mbare O, Lindsay SW, Fillinger U. Testing a pyriproxyfen auto-dissemination station attractive to gravid Anopheles gambiae sensu stricto for the development of a novel attract-release -and-kill strategy for malaria vector control. BMC Infect Dis 2019; 19:800. [PMID: 31510931 PMCID: PMC6740013 DOI: 10.1186/s12879-019-4438-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Accepted: 09/04/2019] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Larviciding is an effective supplementary tool for malaria vector control, but the identification and accessibility of aquatic habitats impedes application. Dissemination of the insect growth regulator, pyriproxyfen (PPF), by gravid Anopheles might constitute a novel application strategy. This study aimed to explore the feasibility of using an attractive bait-station to contaminate gravid Anopheles gambiae sensu stricto with PPF and subsequently transfer PPF to larval habitats. METHODS A bait-station was developed comprising of an artificial pond containing water treated with 20 ppm cedrol, an oviposition attractant, and a netting-cover treated with PPF. Three identical semi-field cages were used to assess the potential of gravid Anopheles to transfer PPF from the bait-station to ponds. Gravid females were released in two semi-field cages, one with PPF on its bait-station (test) and one without PPF (control). No mosquitoes were released in the third cage with a PPF-treated station (control). Transfer of PPF to open ponds was assessed by monitoring emergence of late instar insectary-reared larvae introduced into the ponds. The amount of PPF carried by a mosquito and transferred to water was quantified using liquid chromatography-mass spectrometry. RESULTS In the controls, 86% (95% CI 81-89%) of larvae introduced into open ponds developed into adults, indicating that wind did not distribute PPF in absence of mosquitoes. Emergence inhibition was observed in the test cage but was dependent on the distance between pond and bait-station. Only 25% (95% CI 22-29%) of larvae emerged as adults from ponds 4 m from the bait-station, but 92% (95% CI 89-94%) emerged from ponds 10 m away. Each mosquito was contaminated on average with 112 μg (95% CI 93-123 μg) PPF resulting in the transfer of 230 ng/L (95% CI 180-290 ng/L) PPF to 100 ml volumes of water. CONCLUSIONS The bait-stations successfully attracted gravid females which were subsequently dusted with effective levels of PPF. However, in this study design, attraction and dissemination was limited to short distances. To make this approach feasible for malaria vector control, stronger attractants that lure gravid females from longer distances, in landscapes with many water bodies, and better PPF delivery systems are needed.
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Affiliation(s)
- Oscar Mbare
- International Centre of Insect Physiology and Ecology, Human Health Theme, Nairobi, Kenya
- London School of Hygiene and Tropical Medicine, London, UK
| | | | - Ulrike Fillinger
- International Centre of Insect Physiology and Ecology, Human Health Theme, Nairobi, Kenya
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Waewwab P, Sungvornyothin S, Okanurak K, Soonthornworasiri N, Potiwat R, Raksakoon C. Characteristics of water containers influencing the presence of Aedes immatures in an ecotourism area of Bang Kachao Riverbend, Thailand. JOURNAL OF HEALTH RESEARCH 2019. [DOI: 10.1108/jhr-09-2018-0096] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Purpose
The purpose of this paper is to investigate the influence of breeding containers on the production of Aedes mosquitoes after a vector-control program in households that might support dengue transmission in tourist attraction areas of Bang Kachao Riverbend, Thailand.
Design/methodology/approach
A cross-sectional study was conducted in an ecotourism area of Bang Kachao Riverbend, Thailand, during the period October 2016 to September 2017. A total of 832 households from five villages participated in the study. Data collection employed an interview questionnaire, larval mosquito survey and measurements of the chemical properties of the water in each container. A binary logistic regression model was used to investigate the characteristics of water containers influencing the presence or absence of Aedes immatures.
Findings
The study found that water containers located inside households had a highly presence of Aedes immatures (2.22 times) compared with outdoor containers. Water containers without lids and water containers with ineffective had a high presence of Aedes immatures (3.69 and 2.54 times, respectively). In addition, the chemical properties of the water inside the containers, such as pH, influenced the presence of Aedes immatures (1.76 times) (OR=1.76, 95% CI=1.59–1.96).
Originality/value
The study results emphasized the characteristics of water containers in households located in a tourist attraction area. The findings may inform public health vector-control messages for households located in the tourist attraction area.
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McCormack CP, Ghani AC, Ferguson NM. Fine-scale modelling finds that breeding site fragmentation can reduce mosquito population persistence. Commun Biol 2019; 2:273. [PMID: 31372512 PMCID: PMC6658551 DOI: 10.1038/s42003-019-0525-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/27/2019] [Indexed: 02/03/2023] Open
Abstract
Fine-scale geographic variation in the transmission intensity of mosquito-borne diseases is primarily caused by variation in the density of female adult mosquitoes. Therefore, an understanding of fine-scale mosquito population dynamics is critical to understanding spatial heterogeneity in disease transmission and persistence at those scales. However, mathematical models of dengue and malaria transmission, which consider the dynamics of mosquito larvae, generally do not account for the fragmented structure of larval breeding sites. Here, we develop a stochastic metapopulation model of mosquito population dynamics and explore the impact of accounting for breeding site fragmentation when modelling fine-scale mosquito population dynamics. We find that, when mosquito population densities are low, fragmentation can lead to a reduction in population size, with population persistence dependent on mosquito dispersal and features of the underlying landscape. We conclude that using non-spatial models to represent fine-scale mosquito population dynamics may substantially underestimate the stochastic volatility of those populations.
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Affiliation(s)
- Clare P. McCormack
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
| | - Azra C. Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
| | - Neil M. Ferguson
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG UK
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Boakye DA, Frempong KK, Ogoussan KT, Otoo S, Rebollo Polo M, Dadzie SK, de Souza DK. Implementing a community vector collection strategy for monitoring vector-borne diseases in Ghana. Gates Open Res 2019. [DOI: 10.12688/gatesopenres.12933.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Background: Monitoring vector-borne diseases requires sampling of very large numbers of disease vectors in order to corroborate infections in the human population. This can be challenging, as current vector collection tools are either inefficient, or expensive to implement from a public health perspective. To circumvent this challenge, this study compared a community vector collection strategy using a double-netted mosquito collection method (a tent trap (TT)) to the traditional human landing collection (HLC) method in three communities in lymphatic filariasis-endemic districts in Ghana. Methods: Following community entry and sensitization, community volunteers appointed by the community leaders were trained in the mosquito collection and storage methods and provided with supplies for mosquito collection over a 7-month period. They were visited occasionally by the study team to retrieve the mosquito samples for identification. The collectors were also assessed to evaluate their perspectives on using community vector collectors for monitoring vector-borne diseases. Results: The results of the study indicated that the TT method collected significantly more mosquitoes (63%) over the collection period than HLC (37%). Thus, the TTs were observed to be performing relatively better than the HLC (P<0.001). The collectors knew the importance of mosquitoes in transmitting diseases, could identify the main diseases that were locally transmitted within their communities. They appreciated the involvement of the community in the collection as this enhanced community ownership of the programme as well as providing some financial incentives to those directly involved in the collection. Conclusions: The study revealed that use of community volunteers for the collection of mosquitoes for xenomonitoring purposes can be a viable strategy in the monitoring of vector-borne diseases. However, further development of the strategies and assessments of the costs involved will be required to make this a sustainable approach to monitoring vector-borne disease interventions and enhance community ownership of the programmes.
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Automatic Detection of Open and Vegetated Water Bodies Using Sentinel 1 to Map African Malaria Vector Mosquito Breeding Habitats. REMOTE SENSING 2019. [DOI: 10.3390/rs11050593] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Providing timely and accurate maps of surface water is valuable for mapping malaria risk and targeting disease control interventions. Radar satellite remote sensing has the potential to provide this information but current approaches are not suitable for mapping African malarial mosquito aquatic habitats that tend to be highly dynamic, often with emergent vegetation. We present a novel approach for mapping both open and vegetated water bodies using serial Sentinel-1 imagery for Western Zambia. This region is dominated by the seasonally inundated Upper Zambezi floodplain that suffers from a number of public health challenges. The approach uses open source segmentation and machine learning (extra trees classifier), applied to training data that are automatically derived using freely available ancillary data. Refinement is implemented through a consensus approach and Otsu thresholding to eliminate false positives due to dry flat sandy areas. The results indicate a high degree of accuracy (mean overall accuracy 92% st dev 3.6) providing a tractable solution for operationally mapping water bodies in similar large river floodplain unforested environments. For the period studied, 70% of the total water extent mapped was attributed to vegetated water, highlighting the importance of mapping both open and vegetated water bodies for surface water mapping.
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Boakye DA, Frempong KK, Ogoussan KT, Otoo S, Rebollo Polo M, Dadzie SK, de Souza DK. Implementing a community vector collection strategy for monitoring vector-borne diseases in Ghana. Gates Open Res 2019. [DOI: 10.12688/gatesopenres.12933.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background: Monitoring vector-borne diseases requires sampling of very large numbers of disease vectors in order to corroborate infections in the human population. This can be challenging, as current vector collection tools are either inefficient, or expensive to implement from a public health perspective. To circumvent this challenge, this study compared a community vector collection strategy using a double-netted mosquito collection method (a tent trap (TT)) to the traditional human landing collection (HLC) method in three communities in lymphatic filariasis-endemic districts in Ghana. Methods: Following community entry and sensitization, community volunteers appointed by the community leaders were trained in the mosquito collection and storage methods and provided with supplies for mosquito collection over a 7-month period. They were visited occasionally by the study team to retrieve the mosquito samples for identification. The collectors were also assessed to evaluate their perspectives on using community vector collectors for monitoring vector-borne diseases. Results: The results of the study indicated that the TT method collected significantly more mosquitoes (63%) over the collection period than HLC (37%). Thus, the TTs were observed to be performing relatively better than the HLC (P<0.001). The collectors knew the importance of mosquitoes in transmitting diseases, could identify the main diseases that were locally transmitted within their communities. They appreciated the involvement of the community in the collection as this enhanced community ownership of the programme as well as providing some financial incentives to those directly involved in the collection. Conclusions: The study revealed that use of community volunteers for the collection of mosquitoes for xenomonitoring purposes can be a viable strategy in the monitoring of vector-borne diseases. However, further development of the strategies and assessments of the costs involved will be required to make this a sustainable approach to monitoring vector-borne disease interventions and enhance community ownership of the programmes.
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Eneh LK, Fillinger U, Borg Karlson AK, Kuttuva Rajarao G, Lindh J. Anopheles arabiensis oviposition site selection in response to habitat persistence and associated physicochemical parameters, bacteria and volatile profiles. MEDICAL AND VETERINARY ENTOMOLOGY 2019; 33:56-67. [PMID: 30168151 PMCID: PMC6359949 DOI: 10.1111/mve.12336] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 05/11/2018] [Accepted: 07/24/2018] [Indexed: 05/16/2023]
Abstract
A better understanding of the oviposition behaviour of malaria vectors might facilitate the development of new vector control tools. However, the factors that guide the aquatic habitat selection of gravid females are poorly understood. The present study explored the relative attractiveness of similar artificial ponds (0.8 m2 ) aged at varying lengths prior to opening in such a way that wild Anopheles arabiensis could choose between ponds that were freshly set up, or were aged 4 or 17 days old, to lay eggs. Physicochemical parameters, bacterial profile and volatile organic compounds emitted from ponds were investigated over three experimental rounds. Fresh ponds contained on average twice as many An. arabiensis instar larvae (mean 50, 95% confidence interval (CI) = 29-85) as the ponds that had aged 4 days (mean = 24, 95% CI = 14-42) and 17 days (mean = 20, 95% CI: 12-34). Fresh ponds were associated with a significantly higher turbidity combined with higher water temperature, higher nitrite levels and a lower pH and chlorophyll level than the older ponds. Round by round analyses suggested that bacteria communities differed between age groups and also that 4-heptanone, 2-ethylhexanal and an isomer of octenal were exclusively detected from the fresh ponds. These characteristics may be useful with respect to developing attract and kill strategies for malaria vector control.
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Affiliation(s)
- L K Eneh
- Chemical Ecology, Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - U Fillinger
- International Centre of Insect Physiology and Ecology, Human Health Theme, Thomas Odhiambo Campus, Mbita, Kenya
| | - A K Borg Karlson
- Chemical Ecology, Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - G Kuttuva Rajarao
- Department of Industrial Biotechnology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH, Royal Institute of Technology, Stockholm, Sweden
| | - J Lindh
- Chemical Ecology, Department of Chemistry, School of Engineering Science in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
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Animut A, Negash Y. Dry season occurrence of Anopheles mosquitoes and implications in Jabi Tehnan District, West Gojjam Zone, Ethiopia. Malar J 2018; 17:445. [PMID: 30497495 PMCID: PMC6267885 DOI: 10.1186/s12936-018-2599-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 11/26/2018] [Indexed: 11/20/2022] Open
Abstract
Background Generating evidence on the dry season occurrence of the larval and adult stages of Anopheles mosquitoes helps to design effective malaria vector control strategy as the populations of the vectors is expected to be low. Methods Larval and adult stages of Anopheles were surveyed during dry seasons in Mender Meter, Jiga Yehlmidar and Wongie Berkegn villages, Jabi Tehnan District, West Gojjam Zone, Ethiopia. Larvae were surveyed (along the available surface water collections), sampled, identified into genus, counted and late instars of the genus Anopheles identified into species. Indoor-resting adult mosquitoes were collected using insecticide aerosol spray, processed and identified into species. Data was analysed using SPSS version 20.0 to determine frequencies, mean differences and associations. Results A total of 3127 Anopheles larvae were collected among which most (91.7%; 2869/3127) were from streams followed by ponds (4.3%; 136/3127) and swamps (3.9%; 122/3127). Anopheles gambiae sensu lato was the most prevalent (84.9%; 921/1085) followed by Anopheles cinereus (7.0%; 76/1085), Anopheles chrysti (3.7%; 40/1085), Anopheles demeilloni (2.8%; 30/1085) and Anopheles rhodesiensis (1.6%; 18/1085). The mean number (mean = 15.3) of An. gambiae from Jiga Yehlmidar was significantly (p = 0.024) higher than the corresponding number (mean = 3.2) from Mender Meter. The mean number (mean = 36.3) of An. gambiae larvae in April 2017 was significantly (p = 0.001) higher than the number (mean = 4.0) in December 2013 and the number (mean = 2.6) in March 2013. A total of 1324 adult Anopheles were collected of which the highest proportion (79.1%; 1048/1324) was An. gambiae, followed by An. chrysti (11.7%; 155/1324), An. demeilloni (6%; 80/1324), An. cinereus (2.6%; 35/1324) and Anopheles coustani (0.5%; 6/1324). The highest proportion (54.3%; 569/1048) of the An. gambiae was collected from Wongie Berkegn followed by Jiga Yehlmidar (23.6%; 247/1048) and Mender Meter (22.1%; 232/1048). The mean number (mean = 7.8) of adult An. gambiae caught in Wongie Berkegn was significantly (p = 0.018) higher compared to the number (mean = 3.0) in Mender Meter. No significant difference was observed in the mean number of adult An. gambiae between the seasons. Conclusion and implication Streams were prolific breeding habitats of Anopheles mosquitoes followed by ponds and swamps in the dry seasons. In addition, a high population of indoor resting An. gambiae was caught from indoors. This implies the need for a strengthened vector control during dry seasons using breeding habitat management and improved housing in addition to the existing insecticide (LLINs and IRS) based interventions in Jabi Tehnan District, West Gojjam Zone, Ethiopia.
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Affiliation(s)
- Abebe Animut
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia.
| | - Yohannes Negash
- Aklilu Lemma Institute of Pathobiology, Addis Ababa University, P. O. Box 1176, Addis Ababa, Ethiopia
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Hurtado LA, Rigg CA, Calzada JE, Dutary S, Bernal D, Koo SI, Chaves LF. Population Dynamics of Anopheles albimanus (Diptera: Culicidae) at Ipetí-Guna, a Village in a Region Targeted for Malaria Elimination in Panamá. INSECTS 2018; 9:insects9040164. [PMID: 30453469 PMCID: PMC6316695 DOI: 10.3390/insects9040164] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 07/16/2018] [Accepted: 07/17/2018] [Indexed: 11/20/2022]
Abstract
Anopheles albimanus Wiedemann is a major malaria vector in Mesoamerica and the Caribbean whose population dynamics, in response to changing environments, has been relatively poorly studied. Here, we present monthly adult and larvae data collected from May 2016 to December 2017 in Ipetí-Guna, a village within an area targeted for malaria elimination in the República de Panamá. During the study period we collected a total of 1678 Anopheles spp. mosquitoes (1602 adults and 76 larvae). Over 95% of the collected Anopheles spp. mosquitoes were An. albimanus. Using time series analysis techniques, we found that population dynamics of larvae and adults were not significantly correlated with each other at any time lag, though correlations were highest at one month lag between larvae and adults and four months lag between adults and larvae. Larvae population dynamics had cycles of three months and were sensitive to changes in temperature with 5 months lag, while adult abundance was correlated with itself (1 month lag) and with the normalized difference vegetation index (NDVI) with three months lag. A key observation from our study is the absence of both larvae and adults of An. albimanus between January and April from environments associated with Guna population’s daily activities, which suggests this time window could be the best time to implement elimination campaigns aimed at clearing Plasmodium spp. parasites from Guna populations using, for example, mass drug administration.
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Affiliation(s)
- Lisbeth Amarilis Hurtado
- Departamento de Análisis Epidemiológico y Bioestadísticas, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - Chystrie A Rigg
- Departamento de Investigación en Parasitología, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - José E Calzada
- Departamento de Investigación en Parasitología, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - Sahir Dutary
- Departamento de Análisis Epidemiológico y Bioestadísticas, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - Damaris Bernal
- Departamento de Investigación en Entomología Médica, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - Susana Isabel Koo
- Departamento de Investigación en Entomología Médica, Instituto Conmemorativo Gorgas de Estudios de la Salud, Apartado Postal 0816-02593, Panamá, Republic of Panama.
| | - Luis Fernando Chaves
- Instituto Costarricense de Investigación y Enseñanza en Nutrición y Salud (INCIENSA), Apartado Postal 4-2250, Tres Ríos, Cartago, Costa Rica.
- Programa de Investigación en Enfermedades Tropicales (PIET), Escuela de Medicina Veterinaria, Universidad Nacional, Apartado Postal 304-3000, Heredia, Costa Rica.
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Barbosa S, Kay K, Chitnis N, Hastings IM. Modelling the impact of insecticide-based control interventions on the evolution of insecticide resistance and disease transmission. Parasit Vectors 2018; 11:482. [PMID: 30153869 PMCID: PMC6114906 DOI: 10.1186/s13071-018-3025-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/18/2018] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Current strategies to control mosquito-transmitted infections use insecticides targeted at various stages of the mosquito life-cycle. Control is increasingly compromised by the evolution of insecticide resistance but there is little quantitative understanding of its impact on control effectiveness. We developed a computational approach that incorporates the stage-structured mosquito life-cycle and allows tracking of insecticide resistant genotypes. This approach makes it possible to simultaneously investigate: (i) the population dynamics of mosquitoes throughout their whole life-cycle; (ii) the impact of common vector control interventions on disease transmission; (iii) how these interventions drive the spread of insecticide resistance; and (iv) the impact of resistance once it has arisen and, in particular, whether it is sufficient for malaria transmission to resume. The model consists of a system of difference equations that tracks the immature (eggs, larvae and pupae) and adult stages, for males and females separately, and incorporates density-dependent regulation of mosquito larvae in breeding sites. RESULTS We determined a threshold level of mosquitoes below which transmission of malaria is interrupted. It is based on a classic Ross-Macdonald derivation of the malaria basic reproductive number (R0) and may be used to assess the effectiveness of different control strategies in terms of whether they are likely to interrupt disease transmission. We simulated different scenarios of insecticide deployment by changing key parameters in the model to explore the comparative impact of insecticide treated nets, indoor residual spraying and larvicides. CONCLUSIONS Our simulated results suggest that relatively low degrees of resistance (in terms of reduced mortality following insecticide contact) can induce failure of interventions, and the rate of spread of resistance is faster when insecticides target the larval stages. The optimal disease control strategy depends on vector species demography and local environmental conditions but, in our illustrative parametrisation, targeting larval stages achieved the greatest reduction of the adult population, followed by targeting of non-host-seeking females, as provided by indoor residual spraying. Our approach is designed to be flexible and easily generalizable to many scenarios using different calibrations and to diseases other than malaria.
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Affiliation(s)
- Susana Barbosa
- Parasitology Group, Liverpool School of Tropical Medicine, L3 5QA, Liverpool, UK
- Present address: Université Côte d’Azur, Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Katherine Kay
- Parasitology Group, Liverpool School of Tropical Medicine, L3 5QA, Liverpool, UK
- Present address: Department of Pharmaceutical Sciences, State University of New York at Buffalo, Buffalo, New York 14214 USA
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4002 Basel, Switzerland
- University of Basel, Petersplatz 1, 4003 Basel, Switzerland
| | - Ian M. Hastings
- Parasitology Group, Liverpool School of Tropical Medicine, L3 5QA, Liverpool, UK
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Derua YA, Kahindi SC, Mosha FW, Kweka EJ, Atieli HE, Wang X, Zhou G, Lee M, Githeko AK, Yan G. Microbial larvicides for mosquito control: Impact of long lasting formulations of Bacillus thuringiensis var. israelensis and Bacillus sphaericus on non-target organisms in western Kenya highlands. Ecol Evol 2018; 8:7563-7573. [PMID: 30151171 PMCID: PMC6106196 DOI: 10.1002/ece3.4250] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 04/11/2018] [Accepted: 05/18/2018] [Indexed: 11/14/2022] Open
Abstract
The microbial larvicides Bacillus thuringiensis var. israelensis and Bacillus sphaericus have been used extensively for mosquito control and have been found to be effective and safe to non-target organisms cohabiting with mosquito larvae. Recently developed long lasting microbial larvicides (LLML), although evading the previous challenge of short duration of activity, increase the risk of persistence of toxins in the treated larval habitats. This study monitored the impact of LLML FourStar® and LL3 on non-target organisms cohabiting with mosquito larvae in an operational study to control malaria vectors in western Kenya highlands. A total of 300 larval habitats were selected in three highland villages. The habitats were first monitored for 5 weeks to collect baseline data on non-target organisms cohabiting with mosquito larvae and then randomized into two treatment arms (respective FourStar® and LL3) and one control arm. Non-target organisms were sampled weekly for 5 months after treatment to assess the impact of LLML intervention. Before treatment, the mean density of all non-target organisms combined in the control, LL3 and FourStar® treated habitats was 1.42, 1.39 and 1.49 individuals per habitat per sampling occasion, respectively. Following treatment, this density remained fairly unchanged for 21 weeks at which time it was 1.82, 2.11, and 2.05 for the respective control, LL3 and FourStar® treated habitats. Statistical analysis revealed that LL3 and FourStar® did not significantly alter abundance, richness or diversity of the 11 taxa studied, when comparing the intervention and control larval habitats. However, both FourStar® and LL3 significantly reduced the density of malaria vectors. In conclusion, one round of label rate application of FourStar® or LL3 in natural larval habitats did not alter richness, abundance or diversity of the monitored aquatic non-target organisms cohabiting with mosquito larvae to an ecologically significant level.
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Affiliation(s)
- Yahya A. Derua
- Kilimanjaro Christian Medical University CollegeTumaini University MakumiraMoshiTanzania
- National Institute for Medical ResearchAmani Research CentreTangaTanzania
| | - Samuel C. Kahindi
- Department of ZoologySchool of Pure and Applied SciencesPwani UniversityKilifiKenya
| | - Franklin W. Mosha
- Kilimanjaro Christian Medical University CollegeTumaini University MakumiraMoshiTanzania
| | - Eliningaya J. Kweka
- Division of Livestock and Human Diseases Vector ControlTropical Pesticides Research InstituteArushaTanzania
- Department of Medical Parasitology and EntomologyCatholic University of Health and Allied SciencesMwanzaTanzania
| | | | - Xiaoming Wang
- Program in Public HealthCollege of Health SciencesUniversity of CaliforniaIrvineCalifornia
| | - Guofa Zhou
- Program in Public HealthCollege of Health SciencesUniversity of CaliforniaIrvineCalifornia
| | - Ming‐Chieh Lee
- Program in Public HealthCollege of Health SciencesUniversity of CaliforniaIrvineCalifornia
| | - Andrew K. Githeko
- Climate and Human Health Research UnitCentre for Global Health ResearchKenya Medical Research InstituteKisumuKenya
| | - Guiyun Yan
- Program in Public HealthCollege of Health SciencesUniversity of CaliforniaIrvineCalifornia
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Obopile M, Segoea G, Waniwa K, Ntebela DS, Moakofhi K, Motlaleng M, Mosweunyane T, Edwards JK, Namboze J, Butt W, Manzi M, Takarinda KC, Owiti P. Did microbial larviciding contribute to a reduction in malaria cases in eastern Botswana in 2012-2013? Public Health Action 2018; 8:S50-S54. [PMID: 29713595 DOI: 10.5588/pha.17.0012] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 09/17/2017] [Indexed: 11/10/2022] Open
Abstract
Setting: Larviciding has potential as a component of integrated vector management for the reduction of malaria transmission in Botswana by complementing long-lasting insecticide nets and indoor residual sprays. Objective: To evaluate the susceptibility of local Anopheles to commonly used larvicides. Design: This field test of the efficacy of Bacillus thuringiensis subsp. israliensis vs. Anopheles was performed by measuring larval density before treatment and 24 h and 48 h after treatment in seven sites of Bobirwa district, eastern Botswana, in 2012 and 2013. Vector density and malaria cases were compared between Bobirwa and Ngami (northwestern Botswana), with no larviciding in the control arm. Results: Larviciding reduced larval density by 95% in Bobirwa in 2012, with two cases of malaria, while in 2013 larval density reduction was 81%, with 11 cases. Adult mosquito density was zero for both years in Robelela village (Bobirwa), compared to respectively four and 26 adult mosquitoes per room in Shorobe village (Ngami) in 2012 and 2013. There were no cases of malaria in Robelela in either year, but in Shorobe there were 20 and 70 cases, respectively, in 2012 and 2013. Conclusion: Larviciding can reduce the larval density of mosquitoes and reduce malaria transmission in Botswana. Large-scale, targeted implementation of larviciding in districts at high risk for malaria is recommended.
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Affiliation(s)
- M Obopile
- Botswana University of Agriculture and Natural Resources, Gaborone, Botswana
| | - G Segoea
- National Malaria Programme, Botswana Ministry of Health, Gaborone, Botswana
| | - K Waniwa
- National Malaria Programme, Botswana Ministry of Health, Gaborone, Botswana
| | - D S Ntebela
- National Malaria Programme, Botswana Ministry of Health, Gaborone, Botswana
| | - K Moakofhi
- World Health Organization (WHO) Country Office for Botswana, Gaborone, Botswana
| | - M Motlaleng
- National Malaria Programme, Botswana Ministry of Health, Gaborone, Botswana
| | - T Mosweunyane
- National Malaria Programme, Botswana Ministry of Health, Gaborone, Botswana
| | | | - J Namboze
- Inter-Country Support Team, WHO, Harare, Zimbabwe
| | - W Butt
- Inter-Country Support Team, WHO, Harare, Zimbabwe
| | - M Manzi
- Médecins Sans Frontières, Brussels, Belgium
| | - K C Takarinda
- International Union Against Tuberculosis and Lung Disease, Paris, France
| | - P Owiti
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
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Wondwosen B, Birgersson G, Tekie H, Torto B, Ignell R, Hill SR. Sweet attraction: sugarcane pollen-associated volatiles attract gravid Anopheles arabiensis. Malar J 2018; 17:90. [PMID: 29466989 PMCID: PMC5822481 DOI: 10.1186/s12936-018-2245-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Accepted: 02/18/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Anopheles arabiensis is a key vector for the transmission of human malaria in sub-Saharan Africa. Over the past 10,000 years, humans have successfully cultivated grasses and altered the landscape, creating An. arabiensis favourable environments that contain excellent habitats for both larvae and adults. Sugarcane is the most expanding agricultural system in sub-Saharan Africa, and is linked to the increased threat of malaria in rural communities. The prolific production and wind dispersal of sugarcane pollen, together with standing pools of water, often provide, as a result of irrigation, a nutrient-rich environment for the offspring of gravid malaria mosquitoes. RESULTS In the present study, sugarcane pollen-associated volatiles from two cultivars are shown to attract gravid An. arabiensis in a still air two-port olfactometer and stimulate egg laying in an oviposition bioassay. Through combined gas chromatography and electroantennographic detection, as well as combined gas chromatography and mass spectrometric analyses, we identified the bioactive volatiles and generated a synthetic blend that reproduced the full behavioural repertoire of gravid mosquitoes in the Y-tube assay. Two subtractive odour blends, when compared with the full blend, were significantly more attractive. These three and four-component subtractive blends share the compounds (1R)-(+)-α-pinene, nonanal and benzaldehyde, of which, (1R)-(+)-α-pinene and nonanal are found in the attractive odour blends from rice plants and maize pollen. In pairwise comparisons, the rice synthetic odour blend was more attractive to gravid mosquitoes than either of the pollen blends, whereas the pollen blends did not differ in attraction. CONCLUSIONS The attraction of gravid females to sugarcane pollen volatiles demonstrated in this study, together with the previously found grass-associated volatiles, raise the potential of developing a bioactive chimeric blend to attract gravid malaria mosquitoes. This is discussed in relation to the development of novel and cost-effective vector control measures.
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Affiliation(s)
- Betelehem Wondwosen
- Department of Zoological Sciences, Addis Ababa University, Box 1176, Addis Ababa, Ethiopia
| | - Göran Birgersson
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, Sundsvägen 14, 230 53, Alnarp, Sweden
| | - Habte Tekie
- Department of Zoological Sciences, Addis Ababa University, Box 1176, Addis Ababa, Ethiopia
| | - Baldwyn Torto
- Behavioural and Chemical Ecology Department, International Centre of Insect Physiology and Ecology, P. O. Box 30772, Nairobi, 00100, Kenya
| | - Rickard Ignell
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, Sundsvägen 14, 230 53, Alnarp, Sweden
| | - Sharon R Hill
- Disease Vector Group, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, Sundsvägen 14, 230 53, Alnarp, Sweden.
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Stone CM, Witt AB, Walsh GC, Foster WA, Murphy ST. Would the control of invasive alien plants reduce malaria transmission? A review. Parasit Vectors 2018; 11:76. [PMID: 29391041 PMCID: PMC5793375 DOI: 10.1186/s13071-018-2644-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/12/2018] [Indexed: 12/31/2022] Open
Abstract
Vector control has been the most effective preventive measure against malaria and other vector-borne diseases. However, due to concerns such as insecticide resistance and budget shortfalls, an integrated control approach will be required to ensure sustainable, long-term effectiveness. An integrated management strategy should entail some aspects of environmental management, relying on coordination between various scientific disciplines. Here, we review one such environmental control tactic: invasive alien plant management. This covers salient plant-mosquito interactions for both terrestrial and aquatic invasive plants and how these affect a vector's ability to transmit malaria. Invasive plants tend to have longer flowering durations, more vigorous growth, and their spread can result in an increase in biomass, particularly in areas where previously little vegetation existed. Some invasive alien plants provide shelter or resting sites for adult mosquitoes and are also attractive nectar-producing hosts, enhancing their vectorial capacity. We conclude that these plants may increase malaria transmission rates in certain environments, though many questions still need to be answered, to determine how often this conclusion holds. However, in the case of aquatic invasive plants, available evidence suggests that the management of these plants would contribute to malaria control. We also examine and review the opportunities for large-scale invasive alien plant management, including options for biological control. Finally, we highlight the research priorities that must be addressed in order to ensure that integrated vector and invasive alien plant management operate in a synergistic fashion.
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Affiliation(s)
- Christopher M. Stone
- Illinois Natural History Survey, University of Illinois, Urbana, Champaign, IL 61820 USA
| | - Arne B.R. Witt
- CABI Africa, 673 Limuru Road, Muthaiga, PO Box 633-00621, Nairobi, Kenya
| | - Guillermo Cabrera Walsh
- Fundación para el Estudio de Especies Invasivas (FuEDEI), Bolivar 1559, Hurlingham, Buenos Aires, Argentina
| | - Woodbridge A. Foster
- Department of Evolution, Ecology and Organismal Biology, Ohio State University, Columbus, OH 43210 USA
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Nikookar SH, Fazeli-Dinan M, Azari-Hamidian S, Mousavinasab SN, Arabi M, Ziapour SP, Shojaee J, Enayati A. Species composition and abundance of mosquito larvae in relation with their habitat characteristics in Mazandaran Province, northern Iran. BULLETIN OF ENTOMOLOGICAL RESEARCH 2017; 107:598-610. [PMID: 28956526 DOI: 10.1017/s0007485317000074] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Mosquitoes transmit a variety of diseases to humans. Their abundance and distribution are related to the characteristics of larval habitats. Mosquito larvae were collected from 120 natural and artificial habitats in 30 villages of 16 counties using standard 350 ml dippers and pipette, on a monthly basis from May-December 2014 in Mazandaran Province, northern Iran. Larval habitat characteristics were recorded separately, based on the conditions of the habitats (permanent or temporary, stagnant or running), type of habitats (natural or artificial), vegetation, exposure to sun, type of bed, water condition (clear or turbid), expanse (m), depth (cm, m) and temperature (°C) of habitats. The relationship between larval density and environmental variables was assessed by Chi-square tests. Totally, 19,840 larvae from three genera and 16 species were collected and identified. Anopheles maculipennis s.l. and Culex pipiens were the dominant species and collected with the highest density in plain areas. The highest number of larvae were collected from natural habitats (60.34%), including; river edge, marsh, pit and wetlands; with temporary and stagnant water, expanse of 0-5 m, depth of 1-25 cm, without plant, shadow-sun, muddy floor, turbid water, temperature 20-25°C and in sunny conditions. River edge and rice fields for An. maculipennis s.l and, wetlands and discarded tires for Cx. pipiens were the main larval habitats in the province. Statistical analysis revealed significant relation between occurrence of An. maculipennis s.l., Cx. pipiens, Culex torrentium, Culex mimeticus and Cs. annulata with each of the environmental variables (P < 0.001). These findings are essential in expanding our knowledge of the vectors ecology specially the type of habitat preference and will be beneficial in larval control programs.
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Affiliation(s)
- S H Nikookar
- Student Research Committee,Department of Medical Entomology and Vector Control,Health Sciences Research Center,School of Public Health, Mazandaran University of Medical Sciences,Sari,Iran
| | - M Fazeli-Dinan
- Department of Medical Entomology and Vector Control,School of Public Health and Health Sciences Research Center,Mazandaran University of Medical Science,Sari,Iran
| | - S Azari-Hamidian
- School of Health, Research Center of Health and Environment, Guilan University of Medical Sciences,Rasht,Iran
| | - S N Mousavinasab
- Department of Biostatistics,Mazandaran University of Medical Sciences,Sari,Iran
| | - M Arabi
- Department of Epidemiology, Faculty of Medicine,Mazandaran University of Medical Sciences,Sari,Iran
| | - S P Ziapour
- Student Research Committee,Department of Medical Entomology and Vector Control,Health Sciences Research Center,School of Public Health, Mazandaran University of Medical Sciences,Sari,Iran
| | - J Shojaee
- Health Sciences Research Center,Students Research Committee,Mazandaran University of Medical Sciences,Sari,Iran
| | - A Enayati
- Head of Medical Entomology Department,School of Public Health and Health Sciences Research Center,Mazandaran University of Medical Sciences,Sari,Iran
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Asmare Y, Hopkins RJ, Tekie H, Hill SR, Ignell R. Grass Pollen Affects Survival and Development of Larval Anopheles arabiensis (Diptera: Culicidae). JOURNAL OF INSECT SCIENCE (ONLINE) 2017; 17:4107058. [PMID: 28922900 PMCID: PMC5597869 DOI: 10.1093/jisesa/iex067] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 05/10/2023]
Abstract
Nutrients in breeding sites are critical for the survival and development of malaria mosquitoes, having a direct impact on vectorial capacity. Yet, there is a limited understanding about the natural larval diet and its impact on the individual fitness of mosquitoes. Recent studies have shown that gravid Anopheles arabiensis Patton (Diptera: Culicidae) are attracted by and oviposit in grass-associated habitats. The pollen provided by these grasses is a potential source of nutrients for the larvae. Here, we assess the effect of Typha latifolia L. (Poales: Typhaceae), Echinochloa pyramidalis Lamarck, Pennisetum setaceum Forsskål, and Zea mays L. pollen on larval survival and rate of development in An. arabiensis under laboratory conditions. In addition, we characterize the carbon to nitrogen ratio and the size of pollen grains as a measure of diet quality. Carbon-rich pollen with a small grain size (T. latifolia and P. setaceum; 9.7 ± 0.3 × 103 and 5.5 ± 0.2 × 104 µm3, respectively) resulted in enhanced rates of development of An. arabiensis. In contrast, the larva fed on the nitrogen-rich control diet (TetraMin) was slower to develop, but demonstrated the highest larval survival. Larvae fed on carbon-rich and large-grained Z. mays pollen (4.1 ± 0.2 × 105 µm3) survived at similar levels as those fed on the control diet and also took a longer time to develop compared with larvae fed on the other pollens. While males and females did not appear to develop differently on the different pollen diets, males consistently emerged faster than their female counterparts. These results are discussed in relation to integrated vector management.
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Affiliation(s)
- Yelfwagash Asmare
- Department of Zoological Sciences, Addis Ababa University, PO. Box 1176, Addis Ababa, Ethiopia
- Department of Biological Sciences, Debre Markos University, Debre Markos, Ethiopia
| | - Richard J Hopkins
- Natural Resources Institute, University of Greenwich, London, United Kingdom
| | - Habte Tekie
- Department of Zoological Sciences, Addis Ababa University, PO. Box 1176, Addis Ababa, Ethiopia
| | - Sharon R Hill
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden, and
| | - Rickard Ignell
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Alnarp, Sweden, and
- Corresponding author, e-mail:
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Longbottom J, Browne AJ, Pigott DM, Sinka ME, Golding N, Hay SI, Moyes CL, Shearer FM. Mapping the spatial distribution of the Japanese encephalitis vector, Culex tritaeniorhynchus Giles, 1901 (Diptera: Culicidae) within areas of Japanese encephalitis risk. Parasit Vectors 2017; 10:148. [PMID: 28302156 PMCID: PMC5356256 DOI: 10.1186/s13071-017-2086-8] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/10/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Japanese encephalitis (JE) is one of the most significant aetiological agents of viral encephalitis in Asia. This medically important arbovirus is primarily spread from vertebrate hosts to humans by the mosquito vector Culex tritaeniorhynchus. Knowledge of the contemporary distribution of this vector species is lacking, and efforts to define areas of disease risk greatly depend on a thorough understanding of the variation in this mosquito's geographical distribution. RESULTS We assembled a contemporary database of Cx. tritaeniorhynchus presence records within Japanese encephalitis risk areas from formal literature and other relevant resources, resulting in 1,045 geo-referenced, spatially and temporally unique presence records spanning from 1928 to 2014 (71.9% of records obtained between 2001 and 2014). These presence data were combined with a background dataset capturing sample bias in our presence dataset, along with environmental and socio-economic covariates, to inform a boosted regression tree model predicting environmental suitability for Cx. tritaeniorhynchus at each 5 × 5 km gridded cell within areas of JE risk. The resulting fine-scale map highlights areas of high environmental suitability for this species across India, Nepal and China that coincide with areas of high JE incidence, emphasising the role of this vector in disease transmission and the utility of the map generated. CONCLUSIONS Our map contributes towards efforts determining the spatial heterogeneity in Cx. tritaeniorhynchus distribution within the limits of JE transmission. Specifically, this map can be used to inform vector control programs and can be used to identify key areas where the prevention of Cx. tritaeniorhynchus establishment should be a priority.
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Affiliation(s)
- Joshua Longbottom
- Spatial Ecology & Epidemiology Group, Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Annie J. Browne
- Spatial Ecology & Epidemiology Group, Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - David M. Pigott
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA USA
| | - Marianne E. Sinka
- Oxford Long Term Ecology Laboratory, Department of Zoology, University of Oxford, Oxford, UK
| | - Nick Golding
- Quantitative & Applied Ecology Group, School of BioSciences, University of Melbourne, Parkville, VIC Australia
| | - Simon I. Hay
- Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA USA
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Catherine L. Moyes
- Spatial Ecology & Epidemiology Group, Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Freya M. Shearer
- Spatial Ecology & Epidemiology Group, Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
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Asmare Y, Hill SR, Hopkins RJ, Tekie H, Ignell R. The role of grass volatiles on oviposition site selection by Anopheles arabiensis and Anopheles coluzzii. Malar J 2017; 16:65. [PMID: 28173804 PMCID: PMC5297170 DOI: 10.1186/s12936-017-1717-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Accepted: 01/31/2017] [Indexed: 11/23/2022] Open
Abstract
Background The reproductive success and population dynamics, of Anopheles malaria mosquitoes is strongly influenced by the oviposition site selection of gravid females. Mosquitoes select oviposition sites at different spatial scales, starting with selecting a habitat in which to search. This study utilizes the association of larval abundance in the field with natural breeding habitats, dominated by various types of wild grasses, as a proxy for oviposition site selection by gravid mosquitoes. Moreover, the role of olfactory cues emanating from these habitats in the attraction and oviposition stimulation of females was analysed. Methods The density of Anopheles larvae in breeding sites associated with Echinochloa pyramidalis, Echinochloa stagnina, Typha latifolia and Cyperus papyrus, was sampled and the larvae identified to species level. Headspace volatile extracts of the grasses were collected and used to assess behavioural attraction and oviposition stimulation of gravid Anopheles arabiensis and Anopheles coluzzii mosquitoes in wind tunnel and two-choice oviposition assays, respectively. The ability of the mosquitoes to differentiate among the grass volatile extracts was tested in multi-choice tent assays. Results Anopheles arabiensis larvae were the most abundant species found in the various grass-associated habitats. The larval densities described a hierarchical distribution, with Poaceae (Echinochloa pyramidalis and Echinochloa stagnina)-associated habitat sites demonstrating higher densities than that of Typha-associated sites, and where larvae were absent from Cyperus-associated sites. This hierarchy was maintained by gravid An. arabiensis and An. coluzzii mosquitoes in attraction, oviposition and multi-choice assays to grass volatile extracts. Conclusions The demonstrated hierarchical preference of gravid An. coluzzii and An. arabiensis for grass volatiles indicates that vegetation cues associated with larval habitats are instrumental in the oviposition site choice of the malaria mosquitoes. Identifying volatile cues from grasses that modulate gravid malaria mosquito behaviours has distinct potential for the development of tools to be used in future monitoring and control methods.
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Affiliation(s)
- Yelfwagash Asmare
- Department of Zoological Sciences, Addis Ababa University, PO. Box 1176, Addis Ababa, Ethiopia.,Department of Biological Sciences, Debre Markos University, Debre Markos, Ethiopia
| | - Sharon R Hill
- Department of Plant Protection Biology, Unit of Chemical Ecology, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | | | - Habte Tekie
- Department of Zoological Sciences, Addis Ababa University, PO. Box 1176, Addis Ababa, Ethiopia
| | - Rickard Ignell
- Department of Plant Protection Biology, Unit of Chemical Ecology, Swedish University of Agricultural Sciences, Alnarp, Sweden.
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Dambach P, Schleicher M, Stahl HC, Traoré I, Becker N, Kaiser A, Sié A, Sauerborn R. Routine implementation costs of larviciding with Bacillus thuringiensis israelensis against malaria vectors in a district in rural Burkina Faso. Malar J 2016; 15:380. [PMID: 27449023 PMCID: PMC4957841 DOI: 10.1186/s12936-016-1438-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 07/12/2016] [Indexed: 11/25/2022] Open
Abstract
Background The key tools in malaria control are early diagnosis and treatment of cases as well as vector control. Current strategies for malaria vector control in sub-Saharan Africa are largely based on long-lasting insecticide-treated nets (LLINs) and to a much smaller extent on indoor residual spraying (IRS). An additional tool in the fight against malaria vectors, larval source management (LSM), has not been used in sub-Saharan Africa on a wider scale since the abandonment of environmental spraying of DDT. Increasing concerns about limitations of LLINs and IRS and encouraging results from large larvicide-based LSM trials make a strong case for using biological larviciding as a complementary tool to existing control measures. Arguments that are often quoted against such a combined approach are the alleged high implementation costs of LSM. This study makes the first step to test this argument. The implementation costs of larval source management based on Bacillus thuringiensis israelensis (Bti) (strain AM65-52) spraying under different implementation scenarios were analysed in a rural health district in Burkina Faso. Methods The analysis draws on detailed cost data gathered during a large-scale LSM intervention between 2013 and 2015. All 127 villages in the study setup were assigned to two treatment arms and one control group. Treatment either implied exhaustive spraying of all available water collections or targeted spraying of the 50 % most productive larval sources via remote-sensing derived and entomologically validated risk maps. Based on the cost reports from both intervention arms, the per capita programme costs were calculated under the assumption of covering the whole district with either intervention scenario. Cost calculations have been generalized by providing an adaptable cost formula. In addition, this study assesses the sensitivity of per capita programme costs with respect to changes in the underlying cost components. Results The average annual per capita costs of exhaustive larviciding with Bti during the main malaria transmission period (June–October) in the Nouna health district were calculated to be US$ 1.05. When targeted spraying of the 50 % most productive larval sources is used instead, average annual per capita costs decrease by 27 % to US$ 0.77. Additionally, a high sensitivity of per capita programme costs against changes in total surface of potential larval sources and the number of spraying repetitions was found. Discussion The per capita costs for larval source management interventions with Bti are roughly a third of the annual per capita expenditures for anti-malarial drugs and those for LLINs in Burkina Faso which are US$ 3.80 and 3.00, respectively. The average LSM costs compare to those of IRS and LLINs for sub-Saharan Africa. The authors argue that in such a setting LSM based on Bti spraying is within the range of affordable anti-malarial strategies and, consequently, should deserve more attention in practice. Future research includes a cost-benefit calculation, based on entomological and epidemiological data collected during the research project. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1438-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Peter Dambach
- Institute of Public Health, University of Heidelberg, Heidelberg, Germany.
| | | | | | - Issouf Traoré
- Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
| | - Norbert Becker
- German Mosquito Control Association (KABS), Speyer, Germany.,Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Achim Kaiser
- German Mosquito Control Association (KABS), Speyer, Germany
| | - Ali Sié
- Centre de Recherche en Santé de Nouna, Nouna, Burkina Faso
| | - Rainer Sauerborn
- Institute of Public Health, University of Heidelberg, Heidelberg, Germany
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Low M, Tsegaye AT, Ignell R, Hill S, Elleby R, Feltelius V, Hopkins R. The importance of accounting for larval detectability in mosquito habitat-association studies. Malar J 2016; 15:253. [PMID: 27142303 PMCID: PMC4855760 DOI: 10.1186/s12936-016-1308-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 04/23/2016] [Indexed: 11/10/2022] Open
Abstract
Background Mosquito habitat-association studies are an important basis for disease control programmes and/or vector distribution models. However, studies do not explicitly account for incomplete detection during larval presence and abundance surveys, with potential for significant biases because of environmental influences on larval behaviour and sampling efficiency. Methods Data were used from a dip-sampling study for Anopheles larvae in Ethiopia to evaluate the effect of six factors previously associated with larval sampling (riparian vegetation, direct sunshine, algae, water depth, pH and temperature) on larval presence and detectability. Comparisons were made between: (i) a presence-absence logistic regression where samples were pooled at the site level and detectability ignored, (ii) a success versus trials binomial model, and (iii) a presence-detection mixture model that separately estimated presence and detection, and fitted different explanatory variables to these estimations. Results Riparian vegetation was consistently highlighted as important, strongly suggesting it explains larval presence (−). However, depending on how larval detectability was estimated, the other factors showed large variations in their statistical importance. The presence-detection mixture model provided strong evidence that larval detectability was influenced by sunshine and water temperature (+), with weaker evidence for algae (+) and water depth (−). For larval presence, there was also some evidence that water depth (−) and pH (+) influenced site occupation. The number of dip-samples needed to determine if larvae were likely present at a site was condition dependent: with sunshine and warm water requiring only two dips, while cooler water and cloud cover required 11. Conclusions Environmental factors influence true larval presence and larval detectability differentially when sampling in field conditions. Researchers need to be more aware of the limitations and possible biases in different analytical approaches used to associate larval presence or abundance with local environmental conditions. These effects can be disentangled using data that are routinely collected (i.e., multiple dip samples at each site) by employing a modelling approach that separates presence from detectability. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1308-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Matthew Low
- Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, 75007, Uppsala, Sweden.
| | - Admasu Tassew Tsegaye
- Ethiopian Institute of Water Resources, Addis Ababa University, Addis Ababa, Ethiopia
| | - Rickard Ignell
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, 23053, Alnarp, Sweden
| | - Sharon Hill
- Unit of Chemical Ecology, Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, 23053, Alnarp, Sweden
| | - Rasmus Elleby
- Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, 75007, Uppsala, Sweden.,Department of Earth Sciences, Uppsala University, Uppsala, Sweden
| | - Vilhelm Feltelius
- Department of Ecology, Swedish University of Agricultural Sciences, Box 7044, 75007, Uppsala, Sweden.,Department of Earth Sciences, Uppsala University, Uppsala, Sweden
| | - Richard Hopkins
- Natural Resources Institute, University of Greenwich, London, UK
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Suh E, Choe DH, Saveer AM, Zwiebel LJ. Suboptimal Larval Habitats Modulate Oviposition of the Malaria Vector Mosquito Anopheles coluzzii. PLoS One 2016; 11:e0149800. [PMID: 26900947 PMCID: PMC4768836 DOI: 10.1371/journal.pone.0149800] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 02/04/2016] [Indexed: 01/08/2023] Open
Abstract
Selection of oviposition sites by gravid females is a critical behavioral step in the reproductive cycle of Anopheles coluzzii, which is one of the principal Afrotropical malaria vector mosquitoes. Several studies suggest this decision is mediated by semiochemicals associated with potential oviposition sites. To better understand the chemosensory basis of this behavior and identify compounds that can modulate oviposition, we examined the generally held hypothesis that suboptimal larval habitats give rise to semiochemicals that negatively influence the oviposition preference of gravid females. Dual-choice bioassays indicated that oviposition sites conditioned in this manner do indeed foster significant and concentration dependent aversive effects on the oviposition site selection of gravid females. Headspace analyses derived from aversive habitats consistently noted the presence of dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS) and 6-methyl-5-hepten-2-one (sulcatone) each of which unitarily affected An. coluzzii oviposition preference. Electrophysiological assays across the antennae, maxillary palp, and labellum of gravid An. coluzzii revealed differential responses to these semiochemicals. Taken together, these findings validate the hypothesis in question and suggest that suboptimal environments for An. coluzzii larval development results in the release of DMDS, DMTS and sulcatone that impact the response valence of gravid females.
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Affiliation(s)
- Eunho Suh
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Dong-Hwan Choe
- Department of Entomology, University of California, Riverside, California, United States of America
| | - Ahmed M. Saveer
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Laurence J. Zwiebel
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, United States of America
- Department of Pharmacology, Vanderbilt Brain Institute, Program in Developmental Biology, and Institutes of Chemical Biology and Global Health, Vanderbilt University Medical Center, Tennessee, United States of America
- * E-mail:
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dos Reis IC, Codeço CT, Degener CM, Keppeler EC, Muniz MM, de Oliveira FGS, Cortês JJC, de Freitas Monteiro A, de Souza CAA, Rodrigues FCM, Maia GR, Honório NA. Contribution of fish farming ponds to the production of immature Anopheles spp. in a malaria-endemic Amazonian town. Malar J 2015; 14:452. [PMID: 26573145 PMCID: PMC4647295 DOI: 10.1186/s12936-015-0947-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 10/21/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In the past decade fish farming has become an important economic activity in the Occidental Brazilian Amazon, where the number of new fish farms is rapidly increasing. One of the primary concerns with this phenomenon is the contribution of fishponds to the maintenance and increase of the anopheline mosquito population, and the subsequent increase in human malaria burden. This study reports the results of a 2-year anopheline abundance survey in fishponds and natural water bodies in a malaria-endemic area in northwest Brazil. The objective of this study was to investigate the contribution of natural water bodies (rivers, streams, creeks, ponds, and puddles) and artificial fishponds as breeding sites for Anopheles spp. in Mâncio Lima, Acre and to investigate the effect of limnological and environmental variables on Anopheles spp. larval abundance. METHODS Natural water bodies and fishponds were sampled at eight different times over 2 years (early, mid and late rainy season, dry season) in the Amazonian town of Mâncio Lima, Acre. Anopheline larvae were collected with an entomological dipper, and physical, chemical and ecological characteristics of each water body were measured. Management practices of fishpond owners were ascertained with a systematic questionnaire. RESULTS Fishponds were four times more infested with anopheline larvae than natural water bodies. Electrical conductivity and the distance to the nearest house were both significant inverse predictors of larval abundance in natural water bodies. The density of larvae in fishponds raised with increasing border vegetation. Fishponds owned by different farmers varied in the extent of anopheline larval infestation but ponds owned by the same individual had similar infestation patterns over time. Commercial fishponds were 1.7-times more infested with anopheline larvae compared to fishponds for family use. CONCLUSIONS These results suggest that fishponds are important breeding sites for anopheline larvae, and that adequate management activities, such as removal of border vegetation could reduce the abundance of mosquito larvae, most importantly Anopheles darlingi.
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Affiliation(s)
- Izabel Cristina dos Reis
- Programa de Computação Científica-PROCC, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil.
- Núcleo Operacional Sentinela de Mosquitos Vetores, NOSMOVE (Parceria DIRAC-IOC-VPAAPS/FIOCRUZ), Rio de Janeiro, RJ, Brazil.
| | - Cláudia Torres Codeço
- Programa de Computação Científica-PROCC, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
| | - Carolin Marlen Degener
- Programa de Computação Científica-PROCC, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil.
| | | | - Mauro Menezes Muniz
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil.
| | | | - José Joaquin Carvajal Cortês
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil.
- Núcleo Operacional Sentinela de Mosquitos Vetores, NOSMOVE (Parceria DIRAC-IOC-VPAAPS/FIOCRUZ), Rio de Janeiro, RJ, Brazil.
- Laboratório de Doenças Parasitárias, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil.
| | | | | | | | | | - Nildimar Alves Honório
- Laboratório de Transmissores de Hematozoários, Instituto Oswaldo Cruz (Fiocruz), Rio de Janeiro, RJ, Brazil.
- Núcleo Operacional Sentinela de Mosquitos Vetores, NOSMOVE (Parceria DIRAC-IOC-VPAAPS/FIOCRUZ), Rio de Janeiro, RJ, Brazil.
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Conn JE, Norris DE, Donnelly MJ, Beebe NW, Burkot TR, Coulibaly MB, Chery L, Eapen A, Keven JB, Kilama M, Kumar A, Lindsay SW, Moreno M, Quinones M, Reimer LJ, Russell TL, Smith DL, Thomas MB, Walker ED, Wilson ML, Yan G. Entomological Monitoring and Evaluation: Diverse Transmission Settings of ICEMR Projects Will Require Local and Regional Malaria Elimination Strategies. Am J Trop Med Hyg 2015; 93:28-41. [PMID: 26259942 PMCID: PMC4574272 DOI: 10.4269/ajtmh.15-0009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 05/20/2015] [Indexed: 01/29/2023] Open
Abstract
The unprecedented global efforts for malaria elimination in the past decade have resulted in altered vectorial systems, vector behaviors, and bionomics. These changes combined with increasingly evident heterogeneities in malaria transmission require innovative vector control strategies in addition to the established practices of long-lasting insecticidal nets and indoor residual spraying. Integrated vector management will require focal and tailored vector control to achieve malaria elimination. This switch of emphasis from universal coverage to universal coverage plus additional interventions will be reliant on improved entomological monitoring and evaluation. In 2010, the National Institutes for Allergies and Infectious Diseases (NIAID) established a network of malaria research centers termed ICEMRs (International Centers for Excellence in Malaria Research) expressly to develop this evidence base in diverse malaria endemic settings. In this article, we contrast the differing ecology and transmission settings across the ICEMR study locations. In South America, Africa, and Asia, vector biologists are already dealing with many of the issues of pushing to elimination such as highly focal transmission, proportionate increase in the importance of outdoor and crepuscular biting, vector species complexity, and "sub patent" vector transmission.
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Affiliation(s)
- Jan E. Conn
- *Address correspondence to Jan E. Conn, Griffin Laboratory, The Wadsworth Center, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY 12159. E-mail:
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Okal MN, Lindh JM, Torr SJ, Masinde E, Orindi B, Lindsay SW, Fillinger U. Analysing the oviposition behaviour of malaria mosquitoes: design considerations for improving two-choice egg count experiments. Malar J 2015; 14:250. [PMID: 26088669 PMCID: PMC4474426 DOI: 10.1186/s12936-015-0768-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 06/06/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Choice egg-count bioassays are a popular tool for analysing oviposition substrate preferences of gravid mosquitoes. This study aimed at improving the design of two-choice experiments for measuring oviposition substrates preferences of the malaria vector Anopheles gambiae senso lato, a mosquito that lays single eggs. METHODS In order to achieve high egg-laying success of female An. gambiae sensu stricto (s.s.) and Anopheles arabiensis mosquitoes in experiments, four factors were evaluated: (1) the time provided for mating; (2) the impact of cage size, mosquito age and female body size on insemination; (3) the peak oviposition time; and, (4) the host sources of blood meal. Choice bioassays, with one mosquito released in each cage containing two oviposition cups both with the same oviposition substrate (100 ml water), were used to measure and adjust for egg-laying characteristics of the species. Based on these characteristics an improved design for the egg-count bioassay is proposed. RESULTS High oviposition rates [84%, 95% confidence interval (CI) 77-89%] were achieved when 300 male and 300 blood-fed female An. gambiae s.s. were held together in a cage for 4 days. The chances for oviposition dropped (odds ratio 0.30; 95% CI 0.14-0.66) when human host source of blood meal was substituted with a rabbit but egg numbers per female were not affected. The number of eggs laid by individual mosquitoes was overdispersed (median = 52, eggs, interquartile range 1-214) and the numbers of eggs laid differed widely between replicates, leading to a highly heterogeneous variance between groups and/or rounds of experiments. Moreover, one-third of mosquitoes laid eggs unequally in both cups with similar substrates giving the illusion of choice. Sample size estimations illustrate that it takes 165 individual mosquitoes to power bioassays sufficiently (power = 0.8, p = 0.05) to detect a 15% shift in comparative preferences of two treatments. CONCLUSION Two-choice egg count bioassays with Anopheles are best done with a two-tier design that (1) implements a parallel series of experiments with mosquitoes given a choice of two identical substrates choices and, (2) uses a single mosquito in each test cage rather than groups of mosquitoes to assess the preference of a test or control solution. This approach, with sufficient replication, lowers the risk detecting pseudopreferences.
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Affiliation(s)
- Michael N Okal
- Disease Control Department, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. .,International Centre of Insect Physiology and Ecology, Thomas Odhiambo Campus, Mbita, 40305, Kenya.
| | - Jenny M Lindh
- Royal Institute of Technology, 100 44, Stockholm, Sweden.
| | - Steve J Torr
- Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK. .,Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Elizabeth Masinde
- International Centre of Insect Physiology and Ecology, Thomas Odhiambo Campus, Mbita, 40305, Kenya.
| | - Benedict Orindi
- International Centre of Insect Physiology and Ecology, Biostatistics Unit, Nairobi, 00100, Kenya.
| | - Steve W Lindsay
- School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK.
| | - Ulrike Fillinger
- Disease Control Department, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. .,International Centre of Insect Physiology and Ecology, Thomas Odhiambo Campus, Mbita, 40305, Kenya.
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Chirebvu E, Chimbari MJ. Characteristics of Anopheles arabiensis larval habitats in Tubu village, Botswana. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2015; 40:129-138. [PMID: 26047193 DOI: 10.1111/jvec.12141] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 10/31/2014] [Indexed: 06/04/2023]
Abstract
Documented information on the ecology of larval habitats in Botswana is lacking but is critical for larval control programs. Therefore, this study determined the characteristics of these habitats and the influences of biotic and abiotic factors in Tubu village, Botswana. Eight water bodies were sampled between January and December, 2013. The aquatic vegetation and invertebrate species present were characterized. Water parameters measured were turbidity (NTU), conductivity (μS/cm), oxygen (mg/l), and pH. Larval densities of Anopheles arabiensis mosquitoes and their correlation with abiotic factors were determined. Larval breeding was associated with 'short' aquatic vegetation, a variety of habitats fed by both rainfall and flood waters and sites with predators and competitors. The monthly mean (± SE(mean)) larval density was 8.16±1.33. The monthly mean (±SE(mean)) pH, conductivity, oxygen, and turbidity were 7.65±0.13, 1152.834±69.171, 5.59±1.33, and 323.421±33.801, respectively. There was a significant negative correlation between larval density and conductivity (r = -0.839; p < 0.01), while a significant positive correlation occurred between turbidity and larval density (r = 0.685; p < 0.05). Oxygen (r = 0.140; p > 0.05) and pH (r = 0.252; p > 0.05) were not correlated with larval density. Floods and diversified breeding sites contributed to prolonged and prolific larval breeding. 'Short' aquatic vegetation and predator-infested waters offered suitable environments for larval breeding. Turbidity and conductivity were good indicators for potential breeding places and can be used as early warning indices for predicting larval production levels.
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Affiliation(s)
- Elijah Chirebvu
- Okavango Research Institute, University of Botswana, Private Bag 285, Maun, Botswana.
| | - Moses J Chimbari
- University of Kwazulu-Natal, College of Health Sciences, Howard Campus, Durban, South Africa, 4041
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