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Wagman J, Chanda B, Chanda J, Saili K, Orange E, Mambo P, Muyabe R, Kaniki T, Mwenya M, Ng'andu M, Sakala J, Ngulube W, Miller J, Arnzen A, Silumbe K, Mwaanga G, Simubali L, Mungo A, Mburu MM, Simulundu E, Mambwe B, Kasaro R, Mulube C, Mwenda M, Hamainza B, Ashton RA, Eisele TP, Harris AF, Entwistle J, Yukich J, Slutsker L, Burkot TR, Littrell M. Entomological effects of attractive targeted sugar bait station deployment in Western Zambia: vector surveillance findings from a two-arm cluster randomized phase III trial. Malar J 2024; 23:214. [PMID: 39026236 PMCID: PMC11264679 DOI: 10.1186/s12936-024-05045-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Accepted: 07/16/2024] [Indexed: 07/20/2024] Open
Abstract
BACKGROUND Attractive targeted sugar bait (ATSB) stations are a novel tool with potential to complement current approaches to malaria vector control. To assess the public health value of ATSB station deployment in areas of high coverage with standard vector control, a two-arm cluster-randomized controlled trial (cRCT) of Sarabi ATSB® stations (Westham Ltd., Hod-Hasharon, Israel) was conducted in Western Province, Zambia, a high-burden location were Anopheles funestus is the dominant vector. The trial included 70 clusters and was designed to measure the effect of ATSBs on case incidence and infection prevalence over two 7-month deployments. Reported here are results of the vector surveillance component of the study, conducted in a subset of 20 clusters and designed to provide entomological context to guide overall interpretation of trial findings. METHODS Each month, 200 paired indoor-outdoor human landing catch (HLC) and 200 paired light trap (LT) collections were conducted to monitor An. funestus parity, abundance, biting rates, sporozoite prevalence, and entomological inoculation rates (EIR). RESULTS During the study 20,337 female An. funestus were collected, 11,229 from control and 9,108 from intervention clusters. A subset of 3,131 HLC specimens were assessed for parity: The mean non-parous proportion was 23.0% (95% CI 18.2-28.7%, total n = 1477) in the control and 21.2% (95% CI 18.8-23.9%, total n = 1654) in the intervention arm, an OR = 1.05 (95% CI 0.82-1.34; p = 0.688). A non-significant reduction in LT abundance (RR = 0.65 [95% CI 0.30-1.40, p = 0.267]) was associated with ATSB deployment. HLC rates were highly variable, but model results indicate a similar non-significant trend with a RR = 0.68 (95%CI 0.22-2.00; p = 0.479). There were no effects on sporozoite prevalence or EIR. CONCLUSIONS Anopheles funestus parity did not differ across study arms, but ATSB deployment was associated with a non-significant 35% reduction in vector LT density, results that are consistent with the epidemiological impact reported elsewhere. Additional research is needed to better understand how to maximize the potential impact of ATSB approaches in Zambia and other contexts. TRIAL REGISTRATION NUMBER This trial was registered with Clinicaltrials.gov (NCT04800055, 16 March 2021).
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Ruth A Ashton
- Centre for Applied Malaria Research and Evaluation, Tulane School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | - Thomas P Eisele
- Centre for Applied Malaria Research and Evaluation, Tulane School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | | | | | - Joshua Yukich
- Centre for Applied Malaria Research and Evaluation, Tulane School of Public Health and Tropical Medicine, New Orleans, LA, USA
| | | | - Thomas R Burkot
- Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
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Mwaanga G, Ford J, Yukich J, Chanda B, Ashton RA, Chanda J, Munsanje B, Muntanga E, Mulota M, Simuyandi C, Mulala B, Simubali L, Saili K, Simulundu E, Miller J, Hamainza B, Orange E, Wagman J, Mburu MM, Harris AF, Entwistle J, Littrell M. Residual bioefficacy of attractive targeted sugar bait stations targeting malaria vectors during seasonal deployment in Western Province of Zambia. Malar J 2024; 23:169. [PMID: 38811947 PMCID: PMC11138038 DOI: 10.1186/s12936-024-04990-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Accepted: 05/18/2024] [Indexed: 05/31/2024] Open
Abstract
BACKGROUND The primary vector control interventions in Zambia are long-lasting insecticidal nets and indoor residual spraying. Challenges with these interventions include insecticide resistance and the outdoor biting and resting behaviours of many Anopheles mosquitoes. Therefore, new vector control tools targeting additional mosquito behaviours are needed to interrupt transmission. Attractive targeted sugar bait (ATSB) stations, which exploit the sugar feeding behaviours of mosquitoes, may help in this role. This study evaluated the residual laboratory bioefficacy of Westham prototype ATSB® Sarabi v.1.2.1 Bait Station (Westham Ltd., Hod-Hasharon, Israel) in killing malaria vectors in Western Province, Zambia, during the first year of a large cluster randomized phase-III trial (Clinical Trials.gov Identifier: NCT04800055). METHODS This was a repeat cross-sectional study conducted within three districts, Nkeyema, Kaoma, and Luampa, in Western Province, Zambia. The study was conducted in 12 intervention clusters among the 70 trial clusters (35 interventions, 35 controls) between December 2021 and June 2022. Twelve undamaged bait stations installed on the outer walls of households were collected monthly (one per cluster per month) for bioassays utilizing adult female and male Anopheles gambiae sensu stricto (Kisumu strain) mosquitoes from a laboratory colony. RESULTS A total of 84 field-deployed ATSB stations were collected, and 71 ultimately met the study inclusion criteria for remaining in good condition. Field-deployed stations that remained in good condition (intact, non-depleted of bait, and free of dirt as well as mold) retained high levels of bioefficacy (mean induced mortality of 95.3% in males, 71.3% in females, 83.9% combined total) over seven months in the field but did induce lower mortality rates than non-deployed ATSB stations (mean induced mortality of 96.4% in males, 87.0% in females, 91.4% combined total). There was relatively little variation in corrected mortality rates between monthly rounds for those ATSB stations that had been deployed to the field. CONCLUSION While field-deployed ATSB stations induced lower mortality rates than non-deployed ATSB stations, these stations nonetheless retained relatively high and stable levels of bioefficacy across the 7-month malaria transmission season. While overall mean mosquito mortality rates exceeded 80%, mean mortality rates for females were 24 percentage points lower than among males and these differences merit attention and further evaluation in future studies. The duration of deployment was not associated with lower bioefficacy. Westham prototype ATSB stations can still retain bioefficacy even after deployment in the field for 7 months, provided they do not meet predetermined criteria for replacement.
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Affiliation(s)
| | - Jacob Ford
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
| | - Joshua Yukich
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
| | | | - Ruth A Ashton
- Center for Applied Malaria Research and Evaluation, Department of Tropical Medicine, Tulane University School of Public Health and Tropical Medicine, New Orleans, USA
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Fairbanks EL, Saeung M, Pongsiri A, Vajda E, Wang Y, McIver DJ, Richardson JH, Tatarsky A, Lobo NF, Moore SJ, Ponlawat A, Chareonviriyaphap T, Ross A, Chitnis N. Inference for entomological semi-field experiments: Fitting a mathematical model assessing personal and community protection of vector-control interventions. Comput Biol Med 2024; 168:107716. [PMID: 38039890 DOI: 10.1016/j.compbiomed.2023.107716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 09/19/2023] [Accepted: 11/15/2023] [Indexed: 12/03/2023]
Abstract
The effectiveness of vector-control tools is often assessed by experiments as a reduction in mosquito landings using human landing catches (HLCs). However, HLCs alone only quantify a single characteristic and therefore do not provide information on the overall impacts of the intervention product. Using data from a recent semi-field study which used time-stratified HLCs, aspiration of non-landing mosquitoes, and blood feeding, we suggest a Bayesian inference approach for fitting such data to a stochastic model. This model considers both personal protection, through a reduction in biting, and community protection, from mosquito mortality and disarming (prolonged inhibition of blood feeding). Parameter estimates are then used to predict the reduction of vectorial capacity induced by etofenpox-treated clothing, picaridin topical repellents, transfluthrin spatial repellents and metofluthrin spatial repellents, as well as combined interventions for Plasmodium falciparum malaria in Anopleles minimus. Overall, all interventions had both personal and community effects, preventing biting and killing or disarming mosquitoes. This led to large estimated reductions in the vectorial capacity, with substantial impact even at low coverage. As the interventions aged, fewer mosquitoes were killed; however the impact of some interventions changed from killing to disarming mosquitoes. Overall, this inference method allows for additional modes of action, rather than just reduction in biting, to be parameterised and highlights the tools assessed as promising malaria interventions.
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Affiliation(s)
- Emma L Fairbanks
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland.
| | - Manop Saeung
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Arissara Pongsiri
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | - Elodie Vajda
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | - Yuqian Wang
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - David J McIver
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Allison Tatarsky
- Malaria Elimination Initiative, Institute for Global Health Sciences, University of California, San Francisco, USA
| | | | - Sarah J Moore
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland; Vector Control Product Testing Unit, Ifakara Health Institute, Bagamoyo, United Republic of Tanzania; The Nelson Mandela, African Institution of Science and Technology, School of Life Sciences and Bio Engineering, Tengeru, Arusha, United Republic of Tanzania
| | - Alongkot Ponlawat
- Department of Entomology, Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand
| | | | - Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health, Institute, Allschwill, Switzerland; University of Basel, Basel, Switzerland
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Njoroge TM, Hamid-Adiamoh M, Duman-Scheel M. Maximizing the Potential of Attractive Targeted Sugar Baits (ATSBs) for Integrated Vector Management. INSECTS 2023; 14:585. [PMID: 37504591 PMCID: PMC10380652 DOI: 10.3390/insects14070585] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/23/2023] [Accepted: 06/24/2023] [Indexed: 07/29/2023]
Abstract
Due to the limitations of the human therapeutics and vaccines available to treat and prevent mosquito-borne diseases, the primary strategy for disease mitigation is through vector control. However, the current tools and approaches used for mosquito control have proven insufficient to prevent malaria and arboviral infections, such as dengue, Zika, and lymphatic filariasis, and hence, these diseases remain a global public health threat. The proven ability of mosquito vectors to adapt to various control strategies through insecticide resistance, invasive potential, and behavioral changes from indoor to outdoor biting, combined with human failures to comply with vector control requirements, challenge sustained malaria and arboviral disease control worldwide. To address these concerns, increased efforts to explore more varied and integrated control strategies have emerged. These include approaches that involve the behavioral management of vectors. Attractive targeted sugar baits (ATSBs) are a vector control approach that manipulates and exploits mosquito sugar-feeding behavior to deploy insecticides. Although traditional approaches have been effective in controlling malaria vectors indoors, preventing mosquito bites outdoors and around human dwellings is challenging. ATSBs, which can be used to curb outdoor biting mosquitoes, have the potential to reduce mosquito densities and clinical malaria incidence when used in conjunction with existing vector control strategies. This review examines the available literature regarding the utility of ATSBs for mosquito control, providing an overview of ATSB active ingredients (toxicants), attractants, modes of deployment, target organisms, and the potential for integrating ATSBs with existing vector control interventions.
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Affiliation(s)
- Teresia Muthoni Njoroge
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Raclin-Carmichael Hall, 1234 Notre Dame Ave., South Bend, IN 46617, USA
- Eck Institute for Global Health, The University of Notre Dame, Notre Dame, South Bend, IN 46556, USA
| | - Majidah Hamid-Adiamoh
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Raclin-Carmichael Hall, 1234 Notre Dame Ave., South Bend, IN 46617, USA
- Eck Institute for Global Health, The University of Notre Dame, Notre Dame, South Bend, IN 46556, USA
| | - Molly Duman-Scheel
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Raclin-Carmichael Hall, 1234 Notre Dame Ave., South Bend, IN 46617, USA
- Eck Institute for Global Health, The University of Notre Dame, Notre Dame, South Bend, IN 46556, USA
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Muyaga LL, Meza FC, Kahamba NF, Njalambaha RM, Msugupakulya BJ, Kaindoa EW, Ngowo HS, Okumu FO. Effects of vegetation densities on the performance of attractive targeted sugar baits (ATSBs) for malaria vector control: a semi-field study. Malar J 2023; 22:190. [PMID: 37344867 DOI: 10.1186/s12936-023-04625-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 06/16/2023] [Indexed: 06/23/2023] Open
Abstract
BACKGROUND Attractive targeted sugar baits (ATSBs) control sugar-feeding mosquitoes with oral toxicants, and may effectively complement core malaria interventions, such as insecticide-treated nets even where pyrethroid-resistance is widespread. The technology is particularly efficacious in arid and semi-arid areas. However, their performance remains poorly-understood in tropical areas with year-round malaria transmission, and where the abundant vegetation constitutes competitive sugar sources for mosquitoes. This study compared the efficacies of ATSBs (active ingredient: 2% boric acid) in controlled settings with different vegetation densities. METHODS Potted mosquito-friendly plants were introduced inside semi-field chambers (9.6 m by 9.6 m) to simulate densely-vegetated, sparsely-vegetated, and bare sites without any vegetation (two chambers/category). All chambers had volunteer-occupied huts. Laboratory-reared Anopheles arabiensis were released nightly (200/chamber) and host-seeking females recaptured using human landing catches outdoors (8.00 p.m.-9.00 p.m.) and CDC-light traps indoors (9.00 p.m.-6.00 a.m.). Additionally, resting mosquitoes were collected indoors and outdoors each morning using Prokopack aspirators. The experiments included a "before-and-after" set-up (with pre-ATSBs, ATSBs and post-ATSBs phases per chamber), and a "treatment vs. control" set-up (where similar chambers had ATSBs or no ATSBs). The experiments lasted 84 trap-nights. RESULTS In the initial tests when all chambers had no vegetation, the ATSBs reduced outdoor-biting by 69.7%, indoor-biting by 79.8% and resting mosquitoes by 92.8%. In tests evaluating impact of vegetation, the efficacy of ATSBs against host-seeking mosquitoes was high in bare chambers (outdoors: 64.1% reduction; indoors: 46.8%) but modest or low in sparsely-vegetated (outdoors: 34.5%; indoors: 26.2%) and densely-vegetated chambers (outdoors: 25.4%; indoors: 16.1%). Against resting mosquitoes, the ATSBs performed modestly across settings (non-vegetated chambers: 37.5% outdoors and 38.7% indoors; sparsely-vegetated: 42.9% outdoors and 37.5% indoors; densely-vegetated: 45.5% outdoors and 37.5% indoors). Vegetation significantly reduced the ATSBs efficacies against outdoor-biting and indoor-biting mosquitoes but not resting mosquitoes. CONCLUSION While vegetation can influence the performance of ATSBs, the devices remain modestly efficacious in both sparsely-vegetated and densely-vegetated settings. Higher efficacies may occur in places with minimal or completely no vegetation, but such environments are naturally unlikely to sustain Anopheles populations or malaria transmission in the first place. Field studies therefore remain necessary to validate the efficacies of ATSBs in the tropics.
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Affiliation(s)
- Letus L Muyaga
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania.
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, UK.
| | - Felician C Meza
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
| | - Najat F Kahamba
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Rukiyah M Njalambaha
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
| | - Betwel J Msugupakulya
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Emmanuel W Kaindoa
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- School of Life Sciences and Biotechnology, Nelson Mandela African Institution of Science and Technology, Arusha, United Republic of Tanzania
- Faculty of Health Sciences, School of Pathology, Centre for Emerging Zoonotic and Parasitic Diseases, Wits Research Institute for Malaria, University of the Witwatersrand, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Halfan S Ngowo
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, UK
| | - Fredros O Okumu
- Department of Environmental Health, and Ecological Science, Ifakara Health Institute, Morogoro, United Republic of Tanzania.
- School of Biodiversity, One Health & Veterinary Medicine, University of Glasgow, Glasgow, UK.
- School of Life Sciences and Biotechnology, Nelson Mandela African Institution of Science and Technology, Arusha, United Republic of Tanzania.
- School of Public Health, University of the Witwatersrand, Johannesburg, South Africa.
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Coleman S, Yihdego Y, Gyamfi F, Kolyada L, Tongren JE, Zigirumugabe S, Dery DB, Badu K, Obiri-Danso K, Boakye D, Szumlas D, Armistead JS, Dadzie SK. Estimating malaria transmission risk through surveillance of human-vector interactions in northern Ghana. Parasit Vectors 2023; 16:205. [PMID: 37337221 DOI: 10.1186/s13071-023-05793-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 04/28/2023] [Indexed: 06/21/2023] Open
Abstract
BACKGROUND Vector bionomics are important aspects of vector-borne disease control programs. Mosquito-biting risks are affected by environmental, mosquito behavior and human factors, which are important for assessing exposure risk and intervention impacts. This study estimated malaria transmission risk based on vector-human interactions in northern Ghana, where indoor residual spraying (IRS) and insecticide-treated nets (ITNs) have been deployed. METHODS Indoor and outdoor human biting rates (HBRs) were measured using monthly human landing catches (HLCs) from June 2017 to April 2019. Mosquitoes collected were identified to species level, and Anopheles gambiae sensu lato (An. gambiae s.l.) samples were examined for parity and infectivity. The HBRs were adjusted using mosquito parity and human behavioral observations. RESULTS Anopheles gambiae was the main vector species in the IRS (81%) and control (83%) communities. Indoor and outdoor HBRs were similar in both the IRS intervention (10.6 vs. 11.3 bites per person per night [b/p/n]; z = -0.33, P = 0.745) and control communities (18.8 vs. 16.4 b/p/n; z = 1.57, P = 0.115). The mean proportion of parous An. gambiae s.l. was lower in IRS communities (44.6%) than in control communities (71.7%). After adjusting for human behavior observations and parity, the combined effect of IRS and ITN utilization (IRS: 37.8%; control: 57.3%) on reducing malaria transmission risk was 58% in IRS + ITN communities and 27% in control communities with ITNs alone (z = -4.07, P < 0.001). However, this also revealed that about 41% and 31% of outdoor adjusted bites in IRS and control communities respectively, occurred before bed time (10:00 pm). The mean directly measured annual entomologic inoculation rates (EIRs) during the study were 6.1 infective bites per person per year (ib/p/yr) for IRS communities and 16.3 ib/p/yr for control communities. After considering vector survival and observed human behavior, the estimated EIR for IRS communities was 1.8 ib/p/yr, which represents about a 70% overestimation of risk compared to the directly measured EIR; for control communities, it was 13.6 ib/p/yr (16% overestimation). CONCLUSION Indoor residual spraying significantly impacted entomological indicators of malaria transmission. The results of this study indicate that vector bionomics alone do not provide an accurate assessment of malaria transmission exposure risk. By accounting for human behavior parameters, we found that high coverage of ITNs alone had less impact on malaria transmission indices than combining ITNs with IRS, likely due to observed low net use. Reinforcing effective communication for behavioral change in net use and IRS could further reduce malaria transmission.
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Affiliation(s)
- Sylvester Coleman
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana.
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Yemane Yihdego
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Frank Gyamfi
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Lena Kolyada
- U.S. President's Malaria Initiative VectorLink Project, Accra, Ghana
| | - Jon Eric Tongren
- U.S. President's Malaria Initiative, Malaria Branch, U.S. Centers for Disease Control and Prevention, Accra, Ghana
| | - Sixte Zigirumugabe
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Accra, Ghana
| | - Dominic B Dery
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Accra, Ghana
| | - Kingsley Badu
- Kwame Nkrumah University of Science and Technology, Kumasi, Ghana
| | | | - Daniel Boakye
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
| | - Daniel Szumlas
- Armed Forces Pest Management Board, 172 Forney Road, Forest Glen Annex, Silver Spring, MD, 20910, USA
| | - Jennifer S Armistead
- U.S. President's Malaria Initiative, U.S. Agency for International Development, Washington, DC, USA
| | - Samuel K Dadzie
- Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Accra, Ghana
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Chanda J, Wagman J, Chanda B, Kaniki T, Ng’andu M, Muyabe R, Mwenya M, Sakala J, Miller J, Mwaanga G, Simubali L, Mburu MM, Simulundu E, Mungo A, Fraser K, Mwandigha L, Ashton R, Yukich J, Harris AF, Burkot TR, Orange E, Littrell M, Entwistle J. Feeding rates of malaria vectors from a prototype attractive sugar bait station in Western Province, Zambia: results of an entomological validation study. Malar J 2023; 22:70. [PMID: 36855105 PMCID: PMC9974387 DOI: 10.1186/s12936-023-04491-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Accepted: 02/13/2023] [Indexed: 03/02/2023] Open
Abstract
BACKGROUND Attractive targeted sugar bait (ATSB) stations are a promising new approach to malaria vector control that could compliment current tools by exploiting the natural sugar feeding behaviors of mosquitoes. Recent proof of concept work with a prototype ATSB® Sarabi Bait Station (Westham Co., Hod-Hasharon, Israel) has demonstrated high feeding rates and significant reductions in vector density, human biting rate, and overall entomological inoculation rate for Anopheles gambiae sensu lato (s.l.) in the tropical savannah of western Mali. The study reported here was conducted in the more temperate, rainier region of Western Province, Zambia and was designed to confirm the primary vector species in region and to estimate corresponding rates of feeding from prototype attractive sugar bait (ASB) Sarabi Bait Stations. METHODS The product evaluated was the Sarabi v1.1.1 ASB station, which did not include insecticide but did include 0.8% uranine as a dye allowing for the detection, using UV fluorescence light microscopy, of mosquitoes that have acquired a sugar meal from the ASB. A two-phase, crossover study design was conducted in 10 village-based clusters in Western Province, Zambia. One study arm initially received 2 ASB stations per eligible structure while the other initially received 3. Primary mosquito sampling occurred via indoor and outdoor CDC Miniature UV Light Trap collection from March 01 through April 09, 2021 (Phase 1) and from April 19 to May 28, 2021 (Phase 2). RESULTS The dominant vector in the study area is Anopheles funestus s.l., which was the most abundant species group collected (31% of all Anophelines; 45,038/144,5550), had the highest sporozoite rate (3.16%; 66 positives out of 2,090 tested), and accounted for 94.3% (66/70) of all sporozoite positive specimens. Of those An. funestus specimens further identified to species, 97.2% (2,090/2,150) were An. funestus sensu stricto (s.s.). Anopheles gambiae s.l. (96.8% of which were Anopheles arabiensis) is a likely secondary vector and Anopheles squamosus may play a minor role in transmission. Overall, 21.6% (9,218/42,587) of An. funestus specimens and 10.4% (201/1,940) of An. gambiae specimens collected were positive for uranine, translating into an estimated daily feeding rate of 8.9% [7.7-9.9%] for An. funestus (inter-cluster range of 5.5% to 12.7%) and 3.9% [3.3-4.7%] for An. gambiae (inter-cluster range of 1.0-5.2%). Feeding rates were no different among mosquitoes collected indoors or outdoors, or among mosquitoes from clusters with 2 or 3 ASBs per eligible structure. Similarly, there were no correlations observed between feeding rates and the average number of ASB stations per hectare or with weekly rainfall amounts. CONCLUSIONS Anopheles funestus and An. gambiae vector populations in Western Province, Zambia readily fed from the prototype Sarabi v1.1.1 ASB sugar bait station. Observed feeding rates are in line with those thought to be required for ATSB stations to achieve reductions in malaria transmission when used in combination with conventional control methods (IRS or LLIN). These results supported the decision to implement a large-scale, epidemiological cluster randomized controlled trial of ATSB in Zambia, deploying 2 ATSB stations per eligible structure.
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Affiliation(s)
| | | | | | | | | | | | | | - Jimmy Sakala
- PATH, Lusaka, Zambia ,Present Address: Jhpeigo, Lusaka, Zambia
| | | | | | | | | | | | | | - Keith Fraser
- grid.7445.20000 0001 2113 8111Imperial College London, London, UK
| | - Lazaro Mwandigha
- grid.7445.20000 0001 2113 8111Imperial College London, London, UK ,grid.4991.50000 0004 1936 8948Present Address: University of Oxford, Oxford, UK
| | - Ruth Ashton
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, USA
| | - Joshua Yukich
- grid.265219.b0000 0001 2217 8588School of Public Health and Tropical Medicine, Tulane University, New Orleans, USA
| | | | - Thomas R. Burkot
- grid.1011.10000 0004 0474 1797Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, Australia
| | - Erica Orange
- grid.415269.d0000 0000 8940 7771PATH, Seattle, USA
| | - Megan Littrell
- grid.416809.20000 0004 0423 0663PATH, Washington, DC USA
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Eisele TP, Kleinschmidt I, Sarrassat S, terKuile F, Miller J, Chanda J, Silumbe K, Samuels A, Janssen J, Ogwang C, Bradley J, Orange E, Yukich J, Ashton R, Kyomuhangi I, Harris AF, Doumbia S, Toure M, Moumine M, Majambere S, Mburu MM, Mwaanga G, Simubali L, Simulundu E, Bennett A, Slutsker L, Muller G, Ochomo E, Gimnig J, Johnson PCD, Wagman J, Littrell M. Attractive targeted sugar bait phase III trials in Kenya, Mali, and Zambia. Trials 2022; 23:640. [PMID: 35945599 PMCID: PMC9361277 DOI: 10.1186/s13063-022-06555-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 07/16/2022] [Indexed: 12/03/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) target night-time indoor biting mosquitoes and effectively reduce malaria transmission in rural settings across Africa, but additional vector control tools are needed to interrupt transmission. Attractive targeted sugar baits (ATSBs) attract and kill mosquitoes, including those biting outdoors. Deployment of ATSBs incorporating the insecticide dinotefuran was associated with major reductions in mosquito density and longevity in Mali. The impact of this promising intervention on malaria transmission and morbidity now needs to be determined in a range of transmission settings. METHODS/DESIGN We will conduct three similar stand-alone, open-label, two-arm, cluster-randomized, controlled trials (cRCTs) in Mali, Kenya, and Zambia to determine the impact of ATSB + universal vector control versus universal vector control alone on clinical malaria. The trials will use a "fried-egg" design, with primary outcomes measured in the core area of each cluster to reduce spill-over effects. All household structures in the ATSB clusters will receive two ATSBs, but the impact will be measured in the core of clusters. Restricted randomization will be used. The primary outcome is clinical malaria incidence among children aged 5-14 years in Mali and 1-14 years in Kenya and Zambia. A key secondary outcome is malaria parasite prevalence across all ages. The trials will include 76 clusters (38 per arm) in Mali and 70 (35 per arm) in each of Kenya and Zambia. The trials are powered to detect a 30% reduction in clinical malaria, requiring a total of 3850 person-years of follow-up in Mali, 1260 person-years in Kenya, and 1610 person-years in Zambia. These sample sizes will be ascertained using two seasonal 8-month cohorts in Mali and two 6-month seasonal cohorts in Zambia. In Kenya, which has year-round transmission, four 6-month cohorts will be used (total 24 months of follow-up). The design allows for one interim analysis in Mali and Zambia and two in Kenya. DISCUSSION Strengths of the design include the use of multiple study sites with different transmission patterns and a range of vectors to improve external validity, a large number of clusters within each trial site, restricted randomization, between-cluster separation to minimize contamination between study arms, and an adaptive trial design. Noted threats to internal validity include open-label design, risk of contamination between study arms, risk of imbalance of covariates across study arms, variation in durability of ATSB stations, and potential disruption resulting from the COVID-19 pandemic. TRIAL REGISTRATION Zambia: ClinicalTrials.gov NCT04800055 . Registered on March 15, 2021 Mali: ClinicalTrials.gov NCT04149119 . Registered on November 4, 2019 Kenya: ClinicalTrials.gov NCT05219565 . Registered on February 2, 2022.
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Transfluthrin eave-positioned targeted insecticide (EPTI) reduces human landing rate (HLR) of pyrethroid resistant and susceptible malaria vectors in a semi-field simulated peridomestic space. Malar J 2021; 20:357. [PMID: 34461911 PMCID: PMC8404287 DOI: 10.1186/s12936-021-03880-2] [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: 03/08/2021] [Accepted: 08/15/2021] [Indexed: 02/07/2023] Open
Abstract
Background Volatile pyrethroids (VPs) are proven to reduce human–vector contact for mosquito vectors. With increasing resistance to pyrethroids in mosquitoes, the efficacy of VPs, such as transfluthrin, may be compromised. Therefore, experiments were conducted to determine if the efficacy of transfluthrin eave-positioned targeted insecticide (EPTI) depends on the resistance status of malaria vectors. Methods Ribbons treated with 5.25 g transfluthrin or untreated controls were used around the eaves of an experimental hut as EPTI inside a semi-field system. Mosquito strains with different levels of pyrethroid resistance were released simultaneously, recaptured by means of human landing catches (HLCs) and monitored for 24-h mortality. Technical-grade (TG) transfluthrin was used, followed by emulsifiable concentrate (EC) transfluthrin and additional mosquito strains. Generalized linear mixed models with binomial distribution were used to determine the impact of transfluthrin and mosquito strain on mosquito landing rates and 24-h mortality. Results EPTI treated with 5.25 g of either TG or EC transfluthrin significantly reduced HLR of all susceptible and resistant Anopheles mosquitoes (Odds Ratio (OR) ranging from 0.14 (95% Confidence Interval (CI) [0.11–0.17], P < 0.001) to 0.57, (CI [0.42–0.78] P < 0.001). Both TG and EC EPTI had less impact on landing for the resistant Anopheles arabiensis (Mbita strain) compared to the susceptible Anopheles gambiae (Ifakara strain) (OR 1.50 [95% CI 1.18–1.91] P < 0.001) and (OR 1.67 [95% CI 1.29–2.17] P < 0.001), respectively. The EC EPTI also had less impact on the resistant An. arabiensis (Kingani strain) (OR 2.29 [95% CI 1.78–2.94] P < 0.001) compared to the control however the TG EPTI was equally effective against the resistant Kingani strain and susceptible Ifakara strain (OR 1.03 [95% CI 0.82–1.32] P = 0.75). Finally the EC EPTI was equally effective against the susceptible An. gambiae (Kisumu strain) and the resistant An. gambiae (Kisumu-kdr strain) (OR 0.98 [95% CI 0.74–1.30] P = 0.90). Conclusions Transfluthrin-treated EPTI could be useful in areas with pyrethroid-resistant mosquitoes, but it remains unclear whether stronger resistance to pyrethroids will undermine the efficacy of transfluthrin. At this dosage, transfluthrin EPTI cannot be used to kill exposed mosquitoes. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03880-2.
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10
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Mwandigha LM, Fraser KJ, Racine-Poon A, Mouksassi MS, Ghani AC. Power calculations for cluster randomized trials (CRTs) with right-truncated Poisson-distributed outcomes: a motivating example from a malaria vector control trial. Int J Epidemiol 2021; 49:954-962. [PMID: 32011684 PMCID: PMC7394957 DOI: 10.1093/ije/dyz277] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 12/13/2019] [Accepted: 12/18/2019] [Indexed: 11/14/2022] Open
Abstract
Background Cluster randomized trials (CRTs) are increasingly used to study the efficacy of interventions targeted at the population level. Formulae exist to calculate sample sizes for CRTs, but they assume that the domain of the outcomes being considered covers the full range of values of the considered distribution. This assumption is frequently incorrect in epidemiological trials in which counts of infection episodes are right-truncated due to practical constraints on the number of times a person can be tested. Methods Motivated by a malaria vector control trial with right-truncated Poisson-distributed outcomes, we investigated the effect of right-truncation on power using Monte Carlo simulations. Results The results demonstrate that the adverse impact of right-truncation is directly proportional to the magnitude of the event rate, λ, with calculations of power being overestimated in instances where right-truncation was not accounted for. The severity of the adverse impact of right-truncation on power was more pronounced when the number of clusters was ≤30 but decreased the further the right-truncation point was from zero. Conclusions Potential right-truncation should always be accounted for in the calculation of sample size requirements at the study design stage.
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Affiliation(s)
- Lazaro M Mwandigha
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Keith J Fraser
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
| | - Amy Racine-Poon
- Department of Statistical Methodology and Consulting, Novartis Pharma AG, Basel, Switzerland.,Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Mohamad-Samer Mouksassi
- Bill & Melinda Gates Foundation, Seattle, WA, USA.,Department of Strategic Consulting Integrated Drug Development, Certara, Montreal, QC, Canada.,School of Pharmacy, Department of Pharmaceutical Sciences, Lebanese American University, Byblos, Lebanon.,Faculty of Pharmacy, Department of Pharmaceutical Sciences, University of Montreal, Montreal, QC, Canada
| | - Azra C Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UK
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11
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Fraser KJ, Mwandigha L, Traore SF, Traore MM, Doumbia S, Junnila A, Revay E, Beier JC, Marshall JM, Ghani AC, Müller G. Estimating the potential impact of Attractive Targeted Sugar Baits (ATSBs) as a new vector control tool for Plasmodium falciparum malaria. Malar J 2021; 20:151. [PMID: 33731111 PMCID: PMC7968277 DOI: 10.1186/s12936-021-03684-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 03/05/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Attractive targeted sugar baits (ATSBs) are a promising new tool for malaria control as they can target outdoor-feeding mosquito populations, in contrast to current vector control tools which predominantly target indoor-feeding mosquitoes. METHODS It was sought to estimate the potential impact of these new tools on Plasmodium falciparum malaria prevalence in African settings by combining data from a recent entomological field trial of ATSBs undertaken in Mali with mathematical models of malaria transmission. The key parameter determining impact on the mosquito population is the excess mortality due to ATSBs, which is estimated from the observed reduction in mosquito catch numbers. A mathematical model capturing the life cycle of P. falciparum malaria in mosquitoes and humans and incorporating the excess mortality was used to estimate the potential epidemiological effect of ATSBs. RESULTS The entomological study showed a significant reduction of ~ 57% (95% CI 33-72%) in mosquito catch numbers, and a larger reduction of ~ 89% (95% CI 75-100%) in the entomological inoculation rate due to the fact that, in the presence of ATSBs, most mosquitoes do not live long enough to transmit malaria. The excess mortality due to ATSBs was estimated to be lower (mean 0.09 per mosquito per day, seasonal range 0.07-0.11 per day) than the bait feeding rate obtained from one-day staining tests (mean 0.34 per mosquito per day, seasonal range 0.28-0.38 per day). CONCLUSIONS From epidemiological modelling, it was predicted that ATSBs could result in large reductions (> 30% annually) in prevalence and clinical incidence of malaria, even in regions with an existing high malaria burden. These results suggest that this new tool could provide a promising addition to existing vector control tools and result in significant reductions in malaria burden across a range of malaria-endemic settings.
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Affiliation(s)
- Keith J Fraser
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
| | - Lazaro Mwandigha
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK.,Nuffield Department of Primary Care Health Science, University of Oxford, Oxford, UK
| | - Sekou F Traore
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
| | - Mohamed M Traore
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
| | - Seydou Doumbia
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
| | - Amy Junnila
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
| | - Edita Revay
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - John M Marshall
- Division of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, USA
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Gunter Müller
- Malaria Research and Training Centre, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Sciences, Techniques and Technology of Bamako, BP, Bamako, Mali
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12
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Mwingira VS, Mboera LEG, Takken W. Synergism between nonane and emanations from soil as cues in oviposition-site selection of natural populations of Anopheles gambiae and Culex quinquefasciatus. Malar J 2021; 20:52. [PMID: 33478526 PMCID: PMC7819190 DOI: 10.1186/s12936-020-03575-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Accepted: 12/31/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Olfactory cues have been shown to have an important role in guiding gravid mosquito females to selected sites for egg laying. The objective of this study was to determine the influence of emanations from soil from a breeding site and the putative oviposition pheromone nonane on oviposition-site selection of natural populations of Anopheles gambiae sensu lato (s.l.) and Culex quinquefasciatus. METHODS This field-based study was conducted in Mvomero District in East-central Tanzania. In a dual-choice experimental set up, clay bowls were dug into the ground and filled with one of the following treatments: (i) distilled water + autoclaved soil (control), (ii) distilled water + soil from a natural mosquito breeding site, (iii) distilled water + nonane and (iv) distilled water + nonane + soil from a natural breeding site. Soil was dried and autoclaved or dried only before use. After five days of incubation, larvae were collected daily for 10 days. The median number of larvae per bowl per day was used as outcome measure. RESULTS Autoclaved soil had a significant attractive effect on oviposition behaviour of Cx. quinquefasciatus (median values ± s.e: 8.0 ± 1.1; P < 0.005) but no effect on An. gambiae (median value ± s.e: 0.0 ± 0.2; P = 0.18). Nonane and emanations from untreated soil significantly and positively influenced the selection of oviposition sites by both An. gambiae s.l. (median values ± s.e.: 12.0 ± 2.0 and 4.5 ± 1.5, respectively; P < 0.0001) and Cx. quinquefasciatus (median values ± s.e.: 19.0 ± 1.3 and 17.0 ± 2.0, respectively; P < 0.0001). A mixture of nonane and untreated soil caused a synergistic effect on oviposition behaviour in An. gambiae s.l. (median value ± s.e.: 23.5 ± 2.5; P < 0.0001) compared to either nonane (median values ± s.e.: 12.0 ± 2.0; P < 0.0001) or untreated soil alone (median value ± s.e.: 4.5 ± 1.5; P < 0.0001). A synergistic effect of nonane mixed with untreated soil was also found in Cx. quinquefasciatus (median value ± s.e.: 41.0 ± 2.1; P < 0.0001) compared to either nonane (median value ± s.e. 19.0 ± 1.3; P < 0.0001) or untreated soil alone (median value ± s.e.: 17.0 ± 2.0; P < 0.0001). The oviposition activity index for An. gambiae was 0.56 (P < 0.001) and for Cx. quinquefasciatus 0.59 (P < 0.0001). CONCLUSIONS The larval pheromone nonane and emanations from breeding-site soil both induced oviposition in wild An. gambiae s.l. and Cx. quinquefasciatus, with a synergistic effect when both stimuli were present simultaneously. This is the first study in which nonane is shown to cause oviposition under natural conditions, suggesting that this compound can potentially be exploited for the management of mosquito vectors.
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Affiliation(s)
- Victor S Mwingira
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.,SACIDS Foundation for One Health, Sokoine University of Agriculture, Chuo Kikuu, P.O. Box 3297, Morogoro, Tanzania
| | - Leonard E G Mboera
- SACIDS Foundation for One Health, Sokoine University of Agriculture, Chuo Kikuu, P.O. Box 3297, Morogoro, Tanzania
| | - Willem Takken
- Laboratory of Entomology, Wageningen University & Research, P.O. Box 16, 6700 AA, Wageningen, The Netherlands.
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Sougoufara S, Ottih EC, Tripet F. The need for new vector control approaches targeting outdoor biting Anopheline malaria vector communities. Parasit Vectors 2020; 13:295. [PMID: 32522290 PMCID: PMC7285743 DOI: 10.1186/s13071-020-04170-7] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2020] [Accepted: 06/04/2020] [Indexed: 12/13/2022] Open
Abstract
Since the implementation of Roll Back Malaria, the widespread use of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) is thought to have played a major part in the decrease in mortality and morbidity achieved in malaria-endemic regions. In the past decade, resistance to major classes of insecticides recommended for public health has spread across many malaria vector populations. Increasingly, malaria vectors are also showing changes in vector behaviour in response to current indoor chemical vector control interventions. Changes in the time of biting and proportion of indoor biting of major vectors, as well as changes in the species composition of mosquito communities threaten the progress made to control malaria transmission. Outdoor biting mosquito populations contribute to malaria transmission in many parts of sub-Saharan Africa and pose new challenges as they cannot be reliably monitored or controlled using conventional tools. Here, we review existing and novel approaches that may be used to target outdoor communities of malaria vectors. We conclude that scalable tools designed specifically for the control and monitoring of outdoor biting and resting malaria vectors with increasingly complex and dynamic responses to intensifying malaria control interventions are urgently needed. These are crucial for integrated vector management programmes designed to challenge current and future vector populations.
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Affiliation(s)
- Seynabou Sougoufara
- Centre of Applied Entomology and Parasitology, School of Life Sciences, Keele University, Staffordshire, UK
| | - Emmanuel Chinweuba Ottih
- Centre of Applied Entomology and Parasitology, School of Life Sciences, Keele University, Staffordshire, UK
| | - Frederic Tripet
- Centre of Applied Entomology and Parasitology, School of Life Sciences, Keele University, Staffordshire, UK
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14
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Dahan-Moss Y, Hendershot A, Dhoogra M, Julius H, Zawada J, Kaiser M, Lobo NF, Brooke BD, Koekemoer LL. Member species of the Anopheles gambiae complex can be misidentified as Anopheles leesoni. Malar J 2020; 19:89. [PMID: 32093677 PMCID: PMC7038563 DOI: 10.1186/s12936-020-03168-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 02/17/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Accurate Anopheles species identification is key for effective malaria vector control. Identification primarily depends on morphological analysis of field samples as well as molecular species-specific identifications. During an intra-laboratory assessment (proficiency testing) of the Anopheles funestus group multiplex PCR assay, it was noted that Anopheles arabiensis can be misidentified as Anopheles leesoni, a zoophilic member of the An. funestus group. The aim of this project was, therefore, to ascertain whether other members of the Anopheles gambiae complex can also be misidentified as An. leesoni when using the standard An. funestus multiplex PCR. METHODS The An. funestus multiplex PCR was used to amplify DNA from An. gambiae complex specimens. These included specimens from the laboratory colonies and field samples from the Democratic Republic of Congo. Amplified DNA from these specimens, using the universal (UV) and An. leesoni species-specific primers (LEES), were sequence analysed. Additionally, An. leesoni DNA was processed through the diagnostic An. gambiae multiplex PCR to determine if this species can be misidentified as a member of the An. gambiae complex. RESULTS Laboratory-colonized as well as field-collected samples of An. arabiensis, An. gambiae, Anopheles merus, Anopheles quadriannulatus, Anopheles coluzzii as well as Anopheles moucheti produced an amplicon of similar size to that of An. leesoni when using an An. funestus multiplex PCR. Sequence analysis confirmed that the UV and LEES primers amplify a segment of the ITS2 region of members of the An. gambiae complex and An. moucheti. The reverse was not true, i.e. the An. gambiae multiplex PCR does not amplify DNA from An. leesoni. CONCLUSION This investigation shows that An. arabiensis, An. gambiae, An. merus, An. quadriannulatus, An. coluzzii and An. moucheti can be misidentified as An. leesoni when using An. funestus multiplex PCR. This shows the importance of identifying specimens using standard morphological dichotomous keys as far as possible prior to the use of appropriate PCR-based identification methods. Should there be doubt concerning field-collected specimens molecularly identified as An. leesoni, the An. gambiae multiplex PCR and sequencing of the internal transcribed spacer 2 (ITS2) can be used to eliminate false identifications.
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Affiliation(s)
- Yael Dahan-Moss
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa. .,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Allison Hendershot
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Minishca Dhoogra
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Henry Julius
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa
| | - Jacek Zawada
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Maria Kaiser
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Neil F Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA
| | - Basil D Brooke
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Lizette L Koekemoer
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases of the National Health Laboratory Service, Johannesburg, South Africa.,Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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15
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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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Selvaraj P, Wenger EA, Gerardin J. Seasonality and heterogeneity of malaria transmission determine success of interventions in high-endemic settings: a modeling study. BMC Infect Dis 2018; 18:413. [PMID: 30134861 PMCID: PMC6104018 DOI: 10.1186/s12879-018-3319-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 08/07/2018] [Indexed: 11/15/2022] Open
Abstract
Background Malaria transmission is both seasonal and heterogeneous, and mathematical models that seek to predict the effects of possible intervention strategies should accurately capture realistic seasonality of vector abundance, seasonal dynamics of within-host effects, and heterogeneity of exposure, which may also vary seasonally. Methods Prevalence, incidence, asexual parasite and gametocyte densities, and infectiousness measurements from eight study sites in sub-Saharan Africa were used to calibrate an individual-based model with innate and adaptive immunity. Data from the Garki Project was used to fit exposure rates and parasite densities with month-resolution. A model capturing Garki seasonality and seasonal heterogeneity of exposure was used as a framework for characterizing the infectious reservoir of malaria, testing optimal timing of indoor residual spraying, and comparing four possible mass drug campaign implementations for malaria control. Results Seasonality as observed in Garki sites is neither sinusoidal nor box-like, and substantial heterogeneity in exposure arises from dry-season biting. Individuals with dry-season exposure likely account for the bulk of the infectious reservoir during the dry season even when they are a minority in the overall population. Spray campaigns offer the most benefit in prevalence reduction when implemented just prior to peak vector abundance, which may occur as late as a couple months into the wet season, and targeting spraying to homes of individuals with dry-season exposure can be particularly effective. Expanding seasonal malaria chemoprevention programs to cover older children is predicted to increase the number of cases averted per treatment and is therefore recommended for settings of seasonal and intense transmission. Conclusions Accounting for heterogeneity and seasonality in malaria transmission is critical for understanding transmission dynamics and predicting optimal timing and targeting of control and elimination interventions. Electronic supplementary material The online version of this article (10.1186/s12879-018-3319-y) contains supplementary material, which is available to authorized users.
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Mosquito-Borne Diseases: Prevention Is the Cure for Dengue, Chikungunya and Zika Viruses. PARASITOLOGY RESEARCH MONOGRAPHS 2018. [DOI: 10.1007/978-3-319-94075-5_11] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
This paper summarises key advances and priorities since the 2011 presentation of the Malaria Eradication Research Agenda (malERA), with a focus on the combinations of intervention tools and strategies for elimination and their evaluation using modelling approaches. With an increasing number of countries embarking on malaria elimination programmes, national and local decisions to select combinations of tools and deployment strategies directed at malaria elimination must address rapidly changing transmission patterns across diverse geographic areas. However, not all of these approaches can be systematically evaluated in the field. Thus, there is potential for modelling to investigate appropriate 'packages' of combined interventions that include various forms of vector control, case management, surveillance, and population-based approaches for different settings, particularly at lower transmission levels. Modelling can help prioritise which intervention packages should be tested in field studies, suggest which intervention package should be used at a particular level or stratum of transmission intensity, estimate the risk of resurgence when scaling down specific interventions after local transmission is interrupted, and evaluate the risk and impact of parasite drug resistance and vector insecticide resistance. However, modelling intervention package deployment against a heterogeneous transmission background is a challenge. Further validation of malaria models should be pursued through an iterative process, whereby field data collected with the deployment of intervention packages is used to refine models and make them progressively more relevant for assessing and predicting elimination outcomes.
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Abstract
Since the turn of the century, a remarkable expansion has been achieved in the range and effectiveness of products and strategies available to prevent, treat, and control malaria, including advances in diagnostics, drugs, vaccines, and vector control. These advances have once again put malaria elimination on the agenda. However, it is clear that even with the means available today, malaria control and elimination pose a formidable challenge in many settings. Thus, currently available resources must be used more effectively, and new products and approaches likely to achieve these goals must be developed. This paper considers tools (both those available and others that may be required) to achieve and maintain malaria elimination. New diagnostics are needed to direct treatment and detect transmission potential; new drugs and vaccines to overcome existing resistance and protect against clinical and severe disease, as well as block transmission and prevent relapses; and new vector control measures to overcome insecticide resistance and more powerfully interrupt transmission. It is also essential that strategies for combining new and existing approaches are developed for different settings to maximise their longevity and effectiveness in areas with continuing transmission and receptivity. For areas where local elimination has been recently achieved, understanding which measures are needed to maintain elimination is necessary to prevent rebound and the reestablishment of transmission. This becomes increasingly important as more countries move towards elimination.
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Zhu L, Müller GC, Marshall JM, Arheart KL, Qualls WA, Hlaing WM, Schlein Y, Traore SF, Doumbia S, Beier JC. Is outdoor vector control needed for malaria elimination? An individual-based modelling study. Malar J 2017; 16:266. [PMID: 28673298 PMCID: PMC5496196 DOI: 10.1186/s12936-017-1920-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2017] [Accepted: 06/27/2017] [Indexed: 11/17/2022] Open
Abstract
Background Residual malaria transmission has been reported in many areas even with adequate indoor vector control coverage, such as long-lasting insecticidal nets (LLINs). The increased insecticide resistance in Anopheles mosquitoes has resulted in reduced efficacy of the widely used indoor tools and has been linked with an increase in outdoor malaria transmission. There are considerations of incorporating outdoor interventions into integrated vector management (IVM) to achieve malaria elimination; however, more information on the combination of tools for effective control is needed to determine their utilization. Methods A spatial individual-based model was modified to simulate the environment and malaria transmission activities in a hypothetical, isolated African village setting. LLINs and outdoor attractive toxic sugar bait (ATSB) stations were used as examples of indoor and outdoor interventions, respectively. Different interventions and lengths of efficacy periods were tested. Simulations continued for 420 days, and each simulation scenario was repeated 50 times. Mosquito populations, entomologic inoculation rates (EIRs), probabilities of local mosquito extinction, and proportion of time when the annual EIR was reduced below one were compared between different intervention types and efficacy periods. Results In the village setting with clustered houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population and EIR in short term, increased the probability of local mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one compared to 50% LLINs alone, but there was no significant difference in EIR in short term between 50% LLINs and outdoor ATSBs. In the village setting with dispersed houses, the combinational intervention of 50% LLINs plus outdoor ATSBs significantly reduced mosquito population in short term, increased the probability of mosquito extinction, and increased the time when annual EIR is less than one per person compared to 50% LLINs alone; outdoor ATSBs alone significantly reduced mosquito population in short term, but there were no significant difference in the probability of mosquito extinction and the time when annual EIR is less than one between 50% LLIN and outdoor ATSBs; and there was no significant difference in EIR between all three interventions. A minimum of 2 months of efficacy period is needed to bring out the best possible effect of the vector control tools, and to achieve long-term mosquito reduction, a minimum of 3 months of efficacy period is needed. Conclusions The results highlight the value of incorporating outdoor vector control into IVM as a supplement to traditional indoor practices for malaria elimination in Africa, especially in village settings of clustered houses where LLINs alone is far from sufficient.
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Affiliation(s)
- Lin Zhu
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - Günter C Müller
- Department of Microbiology and Molecular Genetics, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem, Israel.,Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali
| | - John M Marshall
- Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, USA
| | - Kristopher L Arheart
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Whitney A Qualls
- Zoonosis Control Branch, Texas Department of State Health Services, Austin, TX, USA
| | - WayWay M Hlaing
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA
| | - Yosef Schlein
- Department of Microbiology and Molecular Genetics, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem, Israel
| | - Sekou F Traore
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali
| | - Seydou Doumbia
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA
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Thomas MB. Biological control of human disease vectors: a perspective on challenges and opportunities. BIOCONTROL (DORDRECHT, NETHERLANDS) 2017; 63:61-69. [PMID: 29391855 PMCID: PMC5769823 DOI: 10.1007/s10526-017-9815-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2016] [Accepted: 05/03/2017] [Indexed: 05/31/2023]
Abstract
Chemical insecticides are the mainstay of contemporary control of human disease vectors. However, the spread of insecticide resistance and the emergence of new disease threats are creating an urgent need for alternative tools. This perspective paper explores whether biological control might be able to make a greater contribution to vector control in the future, and highlights some of the challenges in taking a technology from initial concept through to operational use. The aim is to stimulate a dialogue within biocontrol and vector control communities, in order to make sure that biological control tools can realize their full potential.
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Affiliation(s)
- Matthew B. Thomas
- Department of Entomology and Center for Infectious Disease Dynamics, Penn State, University Park, PA 16802 USA
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22
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Qualls WA, Naranjo DP, Subía MA, Ramon G, Cevallos V, Grijalva I, Gómez E, Arheart KL, Fuller DO, Beier JC. Movement of Aedes aegypti following a sugar meal and its implication in the development of control strategies in Durán, Ecuador. JOURNAL OF VECTOR ECOLOGY : JOURNAL OF THE SOCIETY FOR VECTOR ECOLOGY 2016; 41:224-231. [PMID: 27860016 DOI: 10.1111/jvec.12217] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Accepted: 06/20/2016] [Indexed: 05/15/2023]
Abstract
We evaluated how the presence of sugar sources impacted the distribution of Aedes aegypti in different habitats in Durán, Ecuador. Land cover and normalized difference vegetation index maps were used to guide a random point sampling routine to select study grids (30 m × 30 m) in low vegetation (LV) and high vegetation (HV). Five individual plants, at one home in the LV and HV grid, were treated with a different colored, non-attractive, 60% sucrose solution to determine mosquito feeding and movement. Sugar alone is not attractive to mosquitoes, so spraying vegetation with a dyed sugar solution can be used for visual determination of sugar feeding. Outdoor collections using BG sentinel traps and indoor collections using aspirators were conducted at the treatment home and with collection points at 20, 40, and 60 m surrounding the treatment home for three consecutive days. A total of 3,245 mosquitoes in two genera, Aedes and Culex, was collected. The proportion of stained Ae. aegypti females was 56.8% (510/898) and 0% for males. For Culex, 63.9% (248/388) females and 36.1% (140/388) males were collected stained. Aedes aegypti and Culex spp. were found up to 60 m stained in both LV and HV grids. Significantly more stained females Ae. aegypti were found inside homes compared to females and males of Culex spp. in both habitats. This study identifies that outdoor sugar feeding is a common behavior of Ae. aegypti and can be targeted as a control strategy in urban habitats in Latin America.
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Affiliation(s)
- Whitney A Qualls
- University of Miami Miller School of Medicine, Department of Public Health Sciences, Miami, FL, U.S.A. 33136
- PROMETEO, Secretaría de Educación Superior, Ciencia, Tecnología e Innovación, Quito, Ecuador
| | - Diana P Naranjo
- University of Miami Miller School of Medicine, Department of Public Health Sciences, Miami, FL, U.S.A. 33136
| | | | - Giovanni Ramon
- Instituto Nacional de Investigación en Salud Pública, Quito, Ecuador
| | - Varsovia Cevallos
- Instituto Nacional de Investigación en Salud Pública, Quito, Ecuador
| | - Isabel Grijalva
- Universidad Católica de Santiago de Guayaquil, Facultad de Ciencias Médicas, Guayas, Ecuador
| | - Eduardo Gómez
- Universidad Católica de Santiago de Guayaquil, Facultad de Ciencias Médicas, Guayas, Ecuador
- Ministerio de Salud Pública del Ecuador
| | - Kristopher L Arheart
- University of Miami Miller School of Medicine, Department of Public Health Sciences, Miami, FL, U.S.A. 33136
| | - Douglas O Fuller
- Department of Geography, University of Miami, Coral Gables, FL 33136, U.S.A
| | - John C Beier
- University of Miami Miller School of Medicine, Department of Public Health Sciences, Miami, FL, U.S.A. 33136
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Faraji A, Unlu I. The Eye of the Tiger, the Thrill of the Fight: Effective Larval and Adult Control Measures Against the Asian Tiger Mosquito, Aedes albopictus (Diptera: Culicidae), in North America. JOURNAL OF MEDICAL ENTOMOLOGY 2016; 53:1029-1047. [PMID: 27354440 DOI: 10.1093/jme/tjw096] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Accepted: 05/11/2016] [Indexed: 06/06/2023]
Abstract
The Asian tiger mosquito, Aedes albopictus (Skuse), is a highly invasive container-inhabiting species with a global distribution. This mosquito, similar to other Stegomyia species such as Aedes aegypti (L.), is highly adapted to urban and suburban areas, and commonly oviposits in artificial containers, which are ubiquitous in these peridomestic environments. The increase in speed and amount of international travel and commerce, coupled with global climate change, have aided in the resurgence and expansion of Stegomyia species into new areas of North America. In many parts of their range, both species are implicated as significant vectors of emerging and re-emerging arboviruses such as dengue, chikungunya, and now Zika. Although rapid and major advances have been made in the field of biology, ecology, genetics, taxonomy, and virology, relatively little has changed in the field of mosquito control in recent decades. This is particularly discouraging in regards to container-inhabiting mosquitoes, because traditional integrated mosquito management (IMM) approaches have not been effective against these species. Many mosquito control programs simply do not possess the man-power or necessary financial resources needed to suppress Ae. albopictus effectively. Therefore, control of mosquito larvae, which is the foundation of IMM approaches, is exceptionally difficult over large areas. This review paper addresses larval habitats, use of geographic information systems for habitat preference detection, door-to-door control efforts, source reduction, direct application of larvicides, biological control agents, area-wide low-volume application of larvicides, hot spot treatments, autodissemination stations, public education, adult traps, attractive-toxic sugar bait methods, lethal ovitraps, barrier-residual adulticides, hand-held ultra-low-volume adulticides, area-wide adulticides applied by ground or air, and genetic control methods. The review concludes with future recommendations for practitioners, researchers, private industry, and policy makers.
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Affiliation(s)
- Ary Faraji
- Salt Lake City Mosquito Abatement District, Salt Lake City, UT 84116 Center for Vector Biology, Department of Entomology, Rutgers University, New Brunswick, NJ 08901
| | - Isik Unlu
- Center for Vector Biology, Department of Entomology, Rutgers University, New Brunswick, NJ 08901 Mercer County Mosquito Control, West Trenton, NJ 08628
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Moore SJ. A new perspective on the application of mosquito repellents. THE LANCET. INFECTIOUS DISEASES 2016; 16:1093-1094. [PMID: 27371976 DOI: 10.1016/s1473-3099(16)30207-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 06/21/2016] [Indexed: 01/11/2023]
Affiliation(s)
- Sarah Jane Moore
- Swiss Tropical and Public Health Institute, Basel CH-4002, Switzerland; University of Basel, Basel, Switzerland; Ifakara Health Institute, Bagamoyo, Pwani, Tanzania.
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Stone C, Chitnis N, Gross K. Environmental influences on mosquito foraging and integrated vector management can delay the evolution of behavioral resistance. Evol Appl 2016; 9:502-17. [PMID: 26989441 PMCID: PMC4778105 DOI: 10.1111/eva.12354] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 12/21/2015] [Indexed: 11/29/2022] Open
Abstract
Along with the scaled‐up distribution of long‐lasting insecticidal nets for malaria control has become concern about insecticide resistance. A related concern regards the evolution of host‐seeking periodicity from the nocturnal to the crepuscular periods of the day. Why we observe such shifts in some areas but not others and which methods could prove useful in managing such behavioral resistance remain open questions. We developed a foraging model to explore whether environmental conditions affect the evolution of behavioral resistance. We looked at the role of the abundance of blood hosts and nectar sources and investigated the potential of attractive toxic sugar baits for integrated control. Higher encounter rates with hosts and nectar sources allowed behaviorally resistant populations to persist at higher levels of bed net coverage. Whereas higher encounter rates with nectar increased the threshold where resistance emerged, higher encounter rates of hosts lowered this threshold. Adding sugar baits lowered the coverage level of bed nets required to eliminate the vector population. In certain environments, using lower bed net coverage levels together with toxic sugar baits may delay or prevent the evolution of behavioral resistance. Designing sustainable control strategies will depend on an understanding of vector behavior expressed in local environmental conditions.
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Affiliation(s)
- Chris Stone
- Department of Statistics North Carolina State University Raleigh NC USA
| | - Nakul Chitnis
- Swiss Tropical and Public Health Institute Basel Switzerland; University of Basel Basel Switzerland
| | - Kevin Gross
- Department of Statistics North Carolina State University Raleigh NC USA
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Alimi TO, Fuller DO, Quinones ML, Xue RD, Herrera SV, Arevalo-Herrera M, Ulrich JN, Qualls WA, Beier JC. Prospects and recommendations for risk mapping to improve strategies for effective malaria vector control interventions in Latin America. Malar J 2015; 14:519. [PMID: 26694047 PMCID: PMC4689006 DOI: 10.1186/s12936-015-1052-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 12/12/2015] [Indexed: 11/10/2022] Open
Abstract
With malaria control in Latin America firmly established in most countries and a growing number of these countries in the pre-elimination phase, malaria elimination appears feasible. A review of the literature indicates that malaria elimination in this region will be difficult without locally tailored strategies for vector control, which depend on more research on vector ecology, genetics and behavioural responses to environmental changes, such as those caused by land cover alterations, and human population movements. An essential way to bridge the knowledge gap and improve vector control is through risk mapping. Malaria risk maps based on statistical and knowledge-based modelling can elucidate the links between environmental factors and malaria vectors, explain interactions between environmental changes and vector dynamics, and provide a heuristic to demonstrate how the environment shapes malaria transmission. To increase the utility of risk mapping in guiding vector control activities, definitions of malaria risk for mapping purposes must be standardized. The maps must also possess appropriate scale and resolution in order to become essential tools in integrated vector management (IVM), so that planners can target areas in greatest need of control measures. Fully integrating risk mapping into vector control programmes will make interventions more evidence-based, making malaria elimination more attainable.
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Affiliation(s)
- Temitope O Alimi
- Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA.
| | - Douglas O Fuller
- Department of Geography and Regional Studies, University of Miami, Coral Gables, FL, USA.
| | - Martha L Quinones
- Department of Public Health, Universidad Nacional de Colombia, Bogota, Colombia.
| | - Rui-De Xue
- Anastasia Mosquito Control District, 500 Old Beach Road, St. Augustine, FL, USA.
| | - Socrates V Herrera
- Centro de Investigacion Cientifica Caucaseco, Universidad del Valle, Cali, Colombia. .,School of Health, Valle State University, Cali, Colombia.
| | - Myriam Arevalo-Herrera
- Centro de Investigacion Cientifica Caucaseco, Universidad del Valle, Cali, Colombia. .,School of Health, Valle State University, Cali, Colombia.
| | - Jill N Ulrich
- Abess Center for Ecosystem Science and Policy, University of Miami, Coral Gables, FL, USA.
| | - Whitney A Qualls
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
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Zhu L, Marshall JM, Qualls WA, Schlein Y, McManus JW, Arheart KL, Hlaing WM, Traore SF, Doumbia S, Müller GC, Beier JC. Modelling optimum use of attractive toxic sugar bait stations for effective malaria vector control in Africa. Malar J 2015; 14:492. [PMID: 26643110 PMCID: PMC4672472 DOI: 10.1186/s12936-015-1012-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 11/24/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The development of insecticide resistance and the increased outdoor-biting behaviour of malaria vectors reduce the efficiency of indoor vector control methods. Attractive toxic sugar baits (ATSBs), a method targeting the sugar-feeding behaviours of vectors both indoors and outdoors, is a promising supplement to indoor tools. The number and configuration of these ATSB stations needed for malaria control in a community needs to be determined. METHODS A hypothetical village, typical of those in sub-Saharan Africa, 600 × 600 m, consisting of houses, humans and essential resource requirements of Anopheles gambiae (sugar sources, outdoor resting sites, larval habitats) was simulated in a spatial individual-based model. Resource-rich and resource-poor environments were simulated separately. Eight types of configurations and different densities of ATSB stations were tested. Anopheles gambiae population size, human biting rate (HBR) and entomological inoculation rates (EIR) were compared between different ATSB configurations and densities. Each simulated scenario was run 50 times. RESULTS Compared to the outcomes not altered by ATSB treatment in the control scenario, in resource-rich and resource-poor environments, respectively, the optimum ATSB treatment reduced female abundance by 98.22 and 91.80 %, reduced HBR by 99.52 and 98.15 %, and reduced EIR by 99.99 and 100 %. In resource-rich environments, n × n grid design, stations at sugar sources, resting sites, larval habitats, and random locations worked better in reducing vector population and HBRs than other configurations (P < 0.0001). However, there was no significant difference of EIR reductions between all ATSB configurations (P > 0.05). In resource-poor environments, there was no significant difference of female abundances, HBRs and EIRs between all ATSB configurations (P > 0.05). The optimum number of ATSB stations was about 25 for resource-rich environments and nine for resource-poor environments. CONCLUSIONS ATSB treatment reduced An. gambiae population substantially and reduced EIR to near zero regardless of environmental resource availability. In resource-rich environments, dispersive configurations worked better in reducing vector population, and stations at or around houses worked better in preventing biting and parasite transmission. In resource-poor environments, all configurations worked similarly. Optimum numbers of bait stations should be adjusted according to seasonality when resource availability changes.
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Affiliation(s)
- Lin Zhu
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - John M Marshall
- Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, USA.
| | - Whitney A Qualls
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - Yosef Schlein
- Department of Microbiology and Molecular Genetics, Faculty of Medicine, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Hebrew University, Jerusalem, Israel.
| | - John W McManus
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA.
| | - Kris L Arheart
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - WayWay M Hlaing
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
| | - Sekou F Traore
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali.
| | - Seydou Doumbia
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali.
| | - Günter C Müller
- Department of Microbiology and Molecular Genetics, Faculty of Medicine, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Hebrew University, Jerusalem, Israel.
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, USA.
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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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Qualls WA, Müller GC, Traore SF, Traore MM, Arheart KL, Doumbia S, Schlein Y, Kravchenko VD, Xue RD, Beier JC. Indoor use of attractive toxic sugar bait (ATSB) to effectively control malaria vectors in Mali, West Africa. Malar J 2015; 14:301. [PMID: 26242186 PMCID: PMC4524285 DOI: 10.1186/s12936-015-0819-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 07/22/2015] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND Attractive toxic sugar bait (ATSB) solutions containing any gut toxins can be either sprayed on plants or used in simple bait stations to attract and kill sugar-feeding female and male mosquitoes. This field study in Mali demonstrates the effect of ATSB bait stations inside houses as a vector control method that targets and kills endophilic African malaria vectors. METHODS The studies were conducted in five villages located near the River Niger, Mali. Baseline village-wide assessments of densities for female and male Anopheles gambiae sensu lato were performed by pyrethrum spray collections (PSC) in ten houses in each of five villages. To determine the rate of mosquito feeding on bait stations, one bait station per house containing attractive sugar bait (ASB) (without toxin) plus a food dye marker, was set up in ten houses in each of the five villages. PSC collections were conducted on the following day and the percentage of female and male mosquitoes that had fed was determined by visual inspection for the dye marker. Then, a 50-day field trial was done. In an experimental village, one bait station containing ATSB (1% boric acid active ingredient) was placed per bedroom (58 bedrooms), and indoor densities of female and male An. gambiae s.l. were subsequently determined by PSC, and female mosquitoes were age graded. RESULTS In the five villages, the percentages of An. gambiae s.l. feeding inside houses on the non-toxic bait stations ranged from 28.3 to 53.1% for females and 36.9 to 78.3% for males. Following ATSB indoor bait station presentation, there was a significant reduction, 90% in female and 93% in male populations, of An. gambiae s.l. at the experimental village. A 3.8-fold decrease in the proportion of females that had undergone four or more gonotrophic cycles was recorded at the experimental village, compared to a 1.2-fold increase at the control village. CONCLUSION The field trial demonstrates that An. gambiae s.l. feed readily from ATSB bait stations situated indoors, leading to a substantial reduction in the proportion of older female mosquitoes. This study demonstrates that ATSB inside houses can achieve impressive malaria vector control in Africa.
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Affiliation(s)
- Whitney A Qualls
- Department of Public Health Sciences, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
| | - Günter C Müller
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Kuvin Centre for the Study of Infectious and Tropical Diseases, Hebrew University, Jerusalem, Israel.
| | - Sekou F Traore
- Faculty of Medicine, Pharmacy and Odontostomatology, Malaria Research and Training Center, University of Bamako, BP 1805, Bamako, Mali.
| | - Mohamed M Traore
- Faculty of Medicine, Pharmacy and Odontostomatology, Malaria Research and Training Center, University of Bamako, BP 1805, Bamako, Mali.
| | - Kristopher L Arheart
- Department of Public Health Sciences, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
| | - Seydou Doumbia
- Faculty of Medicine, Pharmacy and Odontostomatology, Malaria Research and Training Center, University of Bamako, BP 1805, Bamako, Mali.
| | - Yosef Schlein
- Department of Microbiology and Molecular Genetics, IMRIC, Faculty of Medicine, Kuvin Centre for the Study of Infectious and Tropical Diseases, Hebrew University, Jerusalem, Israel.
| | | | - Rui-De Xue
- Anastasia Mosquito Control District, St. Augustine, FL, USA.
| | - John C Beier
- Department of Public Health Sciences, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
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Eckhoff PA, Bever CA, Gerardin J, Wenger EA, Smith DL. From puddles to planet: modeling approaches to vector-borne diseases at varying resolution and scale. CURRENT OPINION IN INSECT SCIENCE 2015; 10:118-123. [PMID: 29587999 DOI: 10.1016/j.cois.2015.05.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 04/27/2015] [Accepted: 05/04/2015] [Indexed: 06/08/2023]
Abstract
Since the original Ross-Macdonald formulations of vector-borne disease transmission, there has been a broad proliferation of mathematical models of vector-borne disease, but many of these models retain most to all of the simplifying assumptions of the original formulations. Recently, there has been a new expansion of mathematical frameworks that contain explicit representations of the vector life cycle including aquatic stages, multiple vector species, host heterogeneity in biting rate, realistic vector feeding behavior, and spatial heterogeneity. In particular, there are now multiple frameworks for spatially explicit dynamics with movements of vector, host, or both. These frameworks are flexible and powerful, but require additional data to take advantage of these features. For a given question posed, utilizing a range of models with varying complexity and assumptions can provide a deeper understanding of the answers derived from models.
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Affiliation(s)
- Philip A Eckhoff
- Institute for Disease Modeling, 1555 132nd Ave NE, Bellevue, WA 98005, USA.
| | - Caitlin A Bever
- Institute for Disease Modeling, 1555 132nd Ave NE, Bellevue, WA 98005, USA
| | - Jaline Gerardin
- Institute for Disease Modeling, 1555 132nd Ave NE, Bellevue, WA 98005, USA
| | - Edward A Wenger
- Institute for Disease Modeling, 1555 132nd Ave NE, Bellevue, WA 98005, USA
| | - David L Smith
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford OX1 3PS, UK; Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA
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Kumar S, Kumari R, Pandey R. New insight-guided approaches to detect, cure, prevent and eliminate malaria. PROTOPLASMA 2015; 252:717-753. [PMID: 25323622 DOI: 10.1007/s00709-014-0697-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 09/01/2014] [Indexed: 06/04/2023]
Abstract
New challenges posed by the development of resistance against artemisinin-based combination therapies (ACTs) as well as previous first-line therapies, and the continuing absence of vaccine, have given impetus to research in all areas of malaria control. This review portrays the ongoing progress in several directions of malaria research. The variants of RTS,S and apical membrane antigen 1 (AMA1) are being developed and test adapted as multicomponent and multistage malaria control vaccines, while many other vaccine candidates and methodologies to produce antigens are under experimentation. To track and prevent the spread of artemisinin resistance from Southeast Asia to other parts of the world, rolling circle-enhanced enzyme activity detection (REEAD), a time- and cost-effective malaria diagnosis in field conditions, and a DNA marker associated with artemisinin resistance have become available. Novel mosquito repellents and mosquito trapping and killing techniques much more effective than the prevalent ones are undergoing field testing. Mosquito lines stably infected with their symbiotic wild-type or genetically engineered bacteria that kill sympatric malaria parasites are being constructed and field tested for stopping malaria transmission. A complementary approach being pursued is the addition of ivermectin-like drug molecules to ACTs to cure malaria and kill mosquitoes. Experiments are in progress to eradicate malaria mosquito by making it genetically male sterile. High-throughput screening procedures are being developed and used to discover molecules that possess long in vivo half life and are active against liver and blood stages for the fast cure of malaria symptoms caused by simple or relapsing and drug-sensitive and drug-resistant types of varied malaria parasites, can stop gametocytogenesis and sporogony and could be given in one dose. Target-based antimalarial drug designing has begun. Some of the putative next-generation antimalarials that possess in their scaffold structure several of the desired properties of malaria cure and control are exemplified by OZ439, NITD609, ELQ300 and tafenoquine that are already undergoing clinical trials, and decoquinate, usnic acid, torin-2, ferroquine, WEHI-916, MMV396749 and benzothiophene-type N-myristoyltransferase (NMT) inhibitors, which are candidates for future clinical usage. Among these, NITD609, ELQ300, decoquinate, usnic acid, torin-2 and NMT inhibitors not only cure simple malaria and are prophylactic against simple malaria, but they also cure relapsing malaria.
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Affiliation(s)
- Sushil Kumar
- SKA Institution for Research, Education and Development (SKAIRED), 4/11 SarvPriya Vihar, New Delhi, 110016, India,
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Zhu L, Qualls WA, Marshall JM, Arheart KL, DeAngelis DL, McManus JW, Traore SF, Doumbia S, Schlein Y, Müller GC, Beier JC. A spatial individual-based model predicting a great impact of copious sugar sources and resting sites on survival of Anopheles gambiae and malaria parasite transmission. Malar J 2015; 14:59. [PMID: 25652678 PMCID: PMC4324791 DOI: 10.1186/s12936-015-0555-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 01/08/2015] [Indexed: 11/28/2022] Open
Abstract
Background Agent-based modelling (ABM) has been used to simulate mosquito life cycles and to evaluate vector control applications. However, most models lack sugar-feeding and resting behaviours or are based on mathematical equations lacking individual level randomness and spatial components of mosquito life. Here, a spatial individual-based model (IBM) incorporating sugar-feeding and resting behaviours of the malaria vector Anopheles gambiae was developed to estimate the impact of environmental sugar sources and resting sites on survival and biting behaviour. Methods A spatial IBM containing An. gambiae mosquitoes and humans, as well as the village environment of houses, sugar sources, resting sites and larval habitat sites was developed. Anopheles gambiae behaviour rules were attributed at each step of the IBM: resting, host seeking, sugar feeding and breeding. Each step represented one second of time, and each simulation was set to run for 60 days and repeated 50 times. Scenarios of different densities and spatial distributions of sugar sources and outdoor resting sites were simulated and compared. Results When the number of natural sugar sources was increased from 0 to 100 while the number of resting sites was held constant, mean daily survival rate increased from 2.5% to 85.1% for males and from 2.5% to 94.5% for females, mean human biting rate increased from 0 to 0.94 bites per human per day, and mean daily abundance increased from 1 to 477 for males and from 1 to 1,428 for females. When the number of outdoor resting sites was increased from 0 to 50 while the number of sugar sources was held constant, mean daily survival rate increased from 77.3% to 84.3% for males and from 86.7% to 93.9% for females, mean human biting rate increased from 0 to 0.52 bites per human per day, and mean daily abundance increased from 62 to 349 for males and from 257 to 1120 for females. All increases were significant (P < 0.01). Survival was greater when sugar sources were randomly distributed in the whole village compared to clustering around outdoor resting sites or houses. Conclusions Increases in densities of sugar sources or outdoor resting sites significantly increase the survival and human biting rates of An. gambiae mosquitoes. Survival of An. gambiae is more supported by random distribution of sugar sources than clustering of sugar sources around resting sites or houses. Density and spatial distribution of natural sugar sources and outdoor resting sites modulate vector populations and human biting rates, and thus malaria parasite transmission.
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Affiliation(s)
- Lin Zhu
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, Florida, USA.
| | - Whitney A Qualls
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, Florida, USA.
| | - John M Marshall
- Department of Infectious Disease Epidemiology, MRC Centre for Outbreak Analysis and Modelling, Imperial College London, London, UK.
| | - Kris L Arheart
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, Florida, USA.
| | - Donald L DeAngelis
- USGS/Biological Resources Division and Department of Biology, University of Miami, Coral Gables, Florida, USA.
| | - John W McManus
- Department of Marine Biology and Ecology, University of Miami, Miami, Florida, USA.
| | - Sekou F Traore
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali.
| | - Seydou Doumbia
- Malaria Research and Training Center, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, BP 1805, Bamako, Mali.
| | - Yosef Schlein
- Department of Microbiology and Molecular Genetics, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem, Israel.
| | - Günter C Müller
- Department of Microbiology and Molecular Genetics, IMRIC, Kuvin Centre for the Study of Infectious and Tropical Diseases, Faculty of Medicine, Hebrew University, Jerusalem, Israel.
| | - John C Beier
- Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, Florida, USA.
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Killeen GF, Kiware SS, Seyoum A, Gimnig JE, Corliss GF, Stevenson J, Drakeley CJ, Chitnis N. Comparative assessment of diverse strategies for malaria vector population control based on measured rates at which mosquitoes utilize targeted resource subsets. Malar J 2014; 13:338. [PMID: 25168421 PMCID: PMC4166001 DOI: 10.1186/1475-2875-13-338] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 08/03/2014] [Indexed: 11/21/2022] Open
Abstract
Background Eliminating malaria requires vector control interventions that dramatically reduce adult mosquito population densities and survival rates. Indoor applications of insecticidal nets and sprays are effective against an important minority of mosquito species that rely heavily upon human blood and habitations for survival. However, complementary approaches are needed to tackle a broader diversity of less human-specialized vectors by killing them at other resource targets. Methods Impacts of strategies that target insecticides to humans or animals can be rationalized in terms of biological coverage of blood resources, quantified as proportional coverage of all blood resources mosquito vectors utilize. Here, this concept is adapted to enable impact prediction for diverse vector control strategies based on measurements of utilization rates for any definable, targetable resource subset, even if that overall resource is not quantifiable. Results The usefulness of this approach is illustrated by deriving utilization rate estimates for various blood, resting site, and sugar resource subsets from existing entomological survey data. Reported impacts of insecticidal nets upon human-feeding vectors, and insecticide-treated livestock upon animal-feeding vectors, are approximately consistent with model predictions based on measured utilization rates for those human and animal blood resource subsets. Utilization rates for artificial sugar baits compare well with blood resources, and are consistent with observed impact when insecticide is added. While existing data was used to indirectly measure utilization rates for a variety of resting site subsets, by comparison with measured rates of blood resource utilization in the same settings, current techniques for capturing resting mosquitoes underestimate this quantity, and reliance upon complex models with numerous input parameters may limit the applicability of this approach. Conclusions While blood and sugar consumption can be readily quantified using existing methods for detecting natural markers or artificial tracers, improved techniques for labelling mosquitoes, or other arthropod pathogen vectors, will be required to assess vector control measures which target them when they utilize non-nutritional resources such as resting, oviposition, and mating sites. Electronic supplementary material The online version of this article (doi:10.1186/1475-2875-13-338) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gerry F Killeen
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Ifakara, Kilombero, Morogoro, United Republic of Tanzania.
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Killeen GF. Characterizing, controlling and eliminating residual malaria transmission. Malar J 2014; 13:330. [PMID: 25149656 PMCID: PMC4159526 DOI: 10.1186/1475-2875-13-330] [Citation(s) in RCA: 303] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/16/2014] [Indexed: 12/02/2022] Open
Abstract
Long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) interventions can reduce malaria transmission by targeting mosquitoes when they feed upon sleeping humans and/or rest inside houses, livestock shelters or other man-made structures. However, many malaria vector species can maintain robust transmission, despite high coverage of LLINs/IRS containing insecticides to which they are physiologically fully susceptible, because they exhibit one or more behaviours that define the biological limits of achievable impact with these interventions: (1) Natural or insecticide-induced avoidance of contact with treated surfaces within houses and early exit from them, thus minimizing exposure hazard of vectors which feed indoors upon humans; (2) Feeding upon humans when they are active and unprotected outdoors, thereby attenuating personal protection and any consequent community-wide suppression of transmission; (3) Feeding upon animals, thus minimizing contact with insecticides targeted at humans or houses; (4) Resting outdoors, away from insecticide-treated surfaces of nets, walls and roofs. Residual malaria transmission is, therefore, defined as all forms of transmission that can persist after achieving full universal coverage with effective LLINs and/or IRS containing active ingredients to which local vector populations are fully susceptible. Residual transmission is sufficiently intense across most of the tropics to render malaria elimination infeasible without new or improved vector control methods. Many novel or improved vector control strategies to address residual transmission are emerging that either: (1) Enhance control of adult vectors that enter houses to feed and/or rest by killing, repelling or excluding them; (2) Kill or repel adult mosquitoes when they attack people outdoors; (3) Kill adult mosquitoes when they attack livestock; (4) Kill adult mosquitoes when they feed upon sugar or; (5) Kill immature mosquitoes in aquatic habitats. To date, none of these options has sufficient supporting evidence to justify full-scale programmatic implementation. Concerted investment in their rigorous selection, development and evaluation is required over the coming decade to enable control and, ultimately, elimination of residual malaria transmission. In the meantime, national programmes may assess options for addressing residual transmission under programmatic conditions through pilot studies with strong monitoring, evaluation and operational research components, similar to the Onchocerciasis Control Programme.
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Affiliation(s)
- Gerry F Killeen
- Ifakara Health Institute, Environmental Health and Ecological Sciences Thematic Group, Ifakara, Morogoro, United Republic of Tanzania.
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Mboera LE, Mazigo HD, Rumisha SF, Kramer RA. Towards malaria elimination and its implication for vector control, disease management and livelihoods in Tanzania. MALARIAWORLD JOURNAL 2013; 4:19. [PMID: 38828111 PMCID: PMC11138750 DOI: 10.5281/zenodo.10928325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/05/2024]
Abstract
Over the years, malaria has remained the number one cause of morbidity and mortality in Tanzania. Population based studies have indicated a decline in overall malaria prevalence among under-fives from 18.1% in 2008 to 9.7% in 2012. The decline of malaria infection has occurred in all geographical zones of the country. Malaria mortality and cumulative probability of deaths have also shown a marked decline from 2000 to 2010. During the same period, area specific studies in Muheza, Korogwe, Muleba and Mvomero have also reported a similar declining trend in malaria prevalence and incidence. The decline in malaria prevalence has been observed to coincide with a decline in transmission indices including anopheline mosquito densities. The decline in malaria prevalence has been attributed to a combination of factors including improved access to effective malaria treatment with artemisinin combination therapy and protection from mosquito bites by increased availability of insecticide treated bednets and indoor residual spraying. The objective of this paper was to review the changing landscape of malaria and its implication for disease management, vector control, and livelihoods in Tanzania. It seeks to examine the links within a broad framework that considers the different pathways given the multiplicity of interactions that can produce unexpected outcomes and trade-offs. Despite the remarkable decline in malaria burden, Tanzania is faced with a number of challenges. These include the development of resistance of malaria vectors to pyrethroids, changing mosquito behaviour and livelihood activities that increase mosquito productivity and exposure to mosquito bites. In addition, there are challenges related to health systems, community perceptions, community involvement and sustainability of funding to the national malaria control programme. This review indicates that malaria remains an important and challenging disease that illustrates the interactions among ecosystems, livelihoods, and health systems. Livelihoods and several sectoral development activities including construction, water resource development and agricultural practices contribute significantly to malaria mosquito productivity and transmission. Consequently, these situations require innovative and integrative re-thinking of the strategies to prevent and control malaria. In conclusion, to accelerate and sustain malaria control in Tanzania, the prevention strategies must go hand in hand with an intersectoral participation approach that takes into account ecosystems and livelihoods that have the potential to increase or decrease malaria transmission.
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Affiliation(s)
- Leonard E.G. Mboera
- National Institute for Medical Research, P.O. Box 9653, Dares Salaam, Tanzania
| | - Humphrey D. Mazigo
- Catholic University of Health and Allied Sciences-Bugando, P.O. Box 1464, Mwanza, Tanzania
| | - Susan F. Rumisha
- National Institute for Medical Research, P.O. Box 9653, Dares Salaam, Tanzania
| | - Randall A. Kramer
- Duke Global Health Institute, Duke University, Durham NC, United States of America
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