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Surit T, Sripoorote P, Kumpitak C, Suansomjit C, Maneechai N, Cui L, Sattabongkot J, Roobsoong W, Nguitragool W. Transmission efficiency of Plasmodium vivax at low parasitaemia. Malar J 2023; 22:22. [PMID: 36658583 PMCID: PMC9854148 DOI: 10.1186/s12936-022-04435-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 12/27/2022] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Plasmodium vivax is responsible for much of malaria outside Africa. Although most P. vivax infections in endemic areas are asymptomatic and have low parasite densities, they are considered a potentially important source of transmission. Several studies have demonstrated that asymptomatic P. vivax carriers can transmit the parasite to mosquitoes, but the efficiency has not been well quantified. The aim of this study is to determine the relationship between parasite density and mosquito infectivity, particularly at low parasitaemia. METHODS Membrane feeding assays were performed using serial dilutions of P. vivax-infected blood to define the relationship between parasitaemia and mosquito infectivity. RESULTS The infection rate (oocyst prevalence) and intensity (oocyst load) were positively correlated with the parasite density in the blood. There was a broad case-to-case variation in parasite infectivity. The geometric mean parasite density yielding a 10% mosquito infection rate was 33 (CI 95 9-120) parasites/µl or 4 (CI 95 1-17) gametocytes/µl. The geometric mean parasite density yielding a 50% mosquito infection rate was 146 (CI 95 36-586) parasites/µl or 13 (CI 95 3-49) gametocytes/µl. CONCLUSION This study quantified the ability of P. vivax to infect Anopheles dirus at over a broad range of parasite densities. It provides important information about parasite infectivity at low parasitaemia common among asymptomatic P. vivax carriers.
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Affiliation(s)
- Thitiporn Surit
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Piyarat Sripoorote
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
| | - Chalermpon Kumpitak
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
| | - Chayanut Suansomjit
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
| | - Nongnuj Maneechai
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
| | - Liwang Cui
- Department of Internal Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL, 33612, USA
| | - Jetsumon Sattabongkot
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand
| | - Wanlapa Roobsoong
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand.
| | - Wang Nguitragool
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Rd, Ratchathewi, Bangkok, 10400, Thailand.
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
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Bantuchai S, Imad H, Nguitragool W. Plasmodium vivax gametocytes and transmission. Parasitol Int 2021; 87:102497. [PMID: 34748969 DOI: 10.1016/j.parint.2021.102497] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 08/14/2021] [Accepted: 10/30/2021] [Indexed: 10/19/2022]
Abstract
Malaria elimination means cessation of parasite transmission. At present, the declining malaria incidence in many countries has made elimination a feasible goal. Transmission control has thus been placed at the center of the national malaria control programs. The efficient transmission of Plasmodium vivax from humans to mosquitoes is a key factor that helps perpetuate malaria in endemic areas. A better understanding of transmission is crucial to the success of elimination efforts. Biological delineation of the parasite transmission process is important for identifying and prioritizing new targets of intervention. Identification of the infectious parasite reservoir in the community is key to devising an effective elimination strategy. Here we describe the fundamental characteristics of P. vivax gametocytes - the dynamics of their production, longevity, and the relationship with the total parasitemia - as well as recent advances in the molecular understanding of parasite sexual development. In relation to malaria elimination, factors influencing the human infectivity and the current evidence for a role of asymptomatic carriers in transmission are presented.
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Affiliation(s)
- Sirasate Bantuchai
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Road, Ratchathewi, Bangkok 10400, Thailand.
| | - Hisham Imad
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Road, Ratchathewi, Bangkok 10400, Thailand.
| | - Wang Nguitragool
- Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Road, Ratchathewi, Bangkok 10400, Thailand; Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchawithi Road, Ratchathewi, Bangkok 10400, Thailand.
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Haileselassie W, Zemene E, Lee MC, Zhong D, Zhou G, Taye B, Dagne A, Deressa W, Kazura JW, Yan G, Yewhalaw D. The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia. Parasit Vectors 2021; 14:516. [PMID: 34620228 PMCID: PMC8500124 DOI: 10.1186/s13071-021-04993-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 09/08/2021] [Indexed: 11/10/2022] Open
Abstract
Background Irrigation schemes may result in subsequent changes in malaria disease dynamics. Understanding the mechanisms and effects of irrigation on malaria vector bionomics and transmission intensity is essential to develop new or alternative surveillance and control strategies to reduce or control malaria risk. This study was designed to assess the effect of rice irrigation on malaria vector bionomics and transmission intensity in the Gambella Region, Ethiopia. Methods Comparative cross-sectional study was conducted in Abobo District of the Gambella Region, Ethiopia. Accordingly, clusters (kebeles) were classified into nearby and faraway clusters depending on their proximity to the irrigation scheme. Adult mosquito survey was conducted in February, August and November 2018 from three nearby and three faraway clusters using Centers for Disease Control and Prevention (CDC) light traps (LTs). During the November survey, human landing catch (HLC) and pyrethrum spray catch (PSC) were also conducted. The collected mosquitoes were morphologically identified to species and tested for Plasmodium infection using circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA). Furthermore, species-specific polymerase chain reaction (PCR) was performed to identify member species of the Anopheles gambiae complex. Chi-square and t-tests were used to analyze the data using the SPSS version 20 software package. Results A total of 4319 female anopheline mosquitoes comprising An. gambiae sensu lato, An. funestus group, An. pharoensis, An. coustani complex and An. squamosus were collected. Overall, 84.5% and 15.5% of the anopheline mosquitoes were collected from the nearby and faraway clusters, respectively. Anopheles gambiae s.l. was the predominant (56.2%) anopheline species in the area followed by An. pharoensis (15.7%). The density of anopheline mosquitoes was significantly higher in the nearby clusters in both HLCs [t(3) = 5.14, P = 0.0143] and CDC LT catches [t(271.97) = 7.446, P < 0.0001). The overall sporozoite rate of anopheline species from the nearby clusters was 10-fold higher compared to the faraway clusters. Conclusions Significantly higher mosquito population density was observed in areas close to the irrigation sites. Sporozoite infection rate in the mosquito population was also markedly higher from the nearby clusters. Therefore, the irrigation scheme could increase the risk of malaria in the area. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04993-y.
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Affiliation(s)
- Werissaw Haileselassie
- School of Public Health, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - Endalew Zemene
- School of Medical Laboratory Sciences, Institute of Health, Jimma University, Jimma, Ethiopia.
| | - Ming-Chieh Lee
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Daibin Zhong
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Guofa Zhou
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Behailu Taye
- Department of Biology, Faculty of Natural and Computational Science, Mettu University, Mettu, Ethiopia
| | - Alemayehu Dagne
- Department of Biology, Faculty of Natural and Computational Science, Mettu University, Mettu, Ethiopia
| | - Wakgari Deressa
- School of Public Health, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia
| | - James W Kazura
- Center for Global Health and Disease, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Guiyun Yan
- Program in Public Health, College of Health Sciences, University of California at Irvine, Irvine, CA, 92697, USA
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Institute of Health, Jimma University, Jimma, Ethiopia.,Tropical and Infectious Diseases Research Centre, Jimma University, Jimma, Ethiopia
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Timinao L, Vinit R, Katusele M, Schofield L, Burkot TR, Karl S. Optimization of the feeding rate of Anopheles farauti s.s. colony mosquitoes in direct membrane feeding assays. Parasit Vectors 2021; 14:356. [PMID: 34233734 PMCID: PMC8261992 DOI: 10.1186/s13071-021-04842-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 06/11/2021] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Direct membrane feeding assays (DMFA) are an important tool to study parasite transmission to mosquitoes. Mosquito feeding rates in these artificial systems require optimization, as there are a number of factors that potentially influence the feeding rates and there are no standardized methods that apply to all anopheline species. METHODS A range of parameters prior to and during direct membrane feeding (DMF) were evaluated for their impact on Anopheles farauti sensu stricto feeding rates, including the starving conditions and duration of starving prior to feeding, membrane type, DMF exposure time, mosquito age, feeding in the light versus the dark, blood volume, mosquito density and temperature of water bath. RESULTS The average successful DMFA feeding rate for An. farauti s.s. colony mosquitoes increased from 50 to 85% when assay parameters were varied. Overnight starvation and Baudruche membrane yielded the highest feeding rates but rates were also affected by blood volume in the feeder and the mosquito density in the feeding cups. Availability of water during the pre-feed starvation period did not significantly impact feeding rates, nor did the exposure duration to blood in membrane feeders, the age of mosquitoes (3, 5 and 7 days post-emergence), feeding in the light versus the dark, or the temperature (34 °C, 38 °C, 42 °C and 46 °C) of the water bath. CONCLUSION Optimal feeding conditions in An. farauti s.s. DMFA were to offer 50 female mosquitoes in a cup (with a total surface area of ~ 340 cm2 with 1 mosquito/6.8 cm2) that were starved overnight 350-500 µL of blood (collected in heparin-coated Vacutainer tubes) per feeder in feeders with a surface area ~ 5 cm2 (with a maximum capacity of 1.5 mL of blood) via a Baudruche membrane, for at least 10-20 min.
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Affiliation(s)
- Lincoln Timinao
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD 4870 Australia
| | - Rebecca Vinit
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Michelle Katusele
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Louis Schofield
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD 4870 Australia
| | - Thomas R. Burkot
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD 4870 Australia
| | - Stephan Karl
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
- Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, QLD 4870 Australia
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Degefa T, Githeko AK, Lee MC, Yan G, Yewhalaw D. Patterns of human exposure to early evening and outdoor biting mosquitoes and residual malaria transmission in Ethiopia. Acta Trop 2021; 216:105837. [PMID: 33485868 DOI: 10.1016/j.actatropica.2021.105837] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 01/10/2021] [Accepted: 01/12/2021] [Indexed: 10/22/2022]
Abstract
Ethiopia has shown a notable progress in reducing malaria burden over the past decade, mainly due to the scaleup of vector control interventions such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS). Based on the progress, the country has set goals to eliminate malaria by 2030. However, residual malaria transmission due to early evening and outdoor biting vectors could pose a challenge to malaria elimination efforts. This study assessed vector behavior, patterns of human exposure to vector bites and residual malaria transmission in southwestern Ethiopia. Anopheles mosquitoes were collected monthly from January to December 2018 using human landing catches (HLCs), human-baited double net traps, CDC light traps and pyrethrum spray catches. Human behavior data were collected using questionnaire to estimate the magnitude of human exposure to mosquito bites occurring indoors and outdoors at various times of the night. Enzyme-linked immunosorbent assay (ELISA) was used to determine mosquito blood meal sources and sporozoite infections. A total of 2,038 female Anopheles mosquitoes comprising Anopheles arabiensis (30.8%), An. pharoensis (40.5%), An. coustani (28.1%), An. squamosus (0.3%) and An. funestus group (0.2%) were collected. Anopheles arabiensis and An. pharoensis were 2.4 and 2.5 times more likely to seek hosts outdoors than indoors, respectively. However, 66% of human exposure to An. arabiensis and 39% of exposure to An. pharoensis bites occurred indoors for LLIN non-users. For LLIN users, 75% of residual exposure to An. arabiensis bites occurred outdoors while 23% occurred indoors before bed time. Likewise, 84% of residual exposure to An. pharoensis bites occurred outdoors while 15% occurred indoors before people retired to bed. Anopheles arabiensis and An. pharoensis were 4.1 and 4.8 times more likely to feed on bovine than humans, respectively. Based on the HLC, an estimated indoor and outdoor EIR of An. arabiensis was 6.2 and 1.4 infective bites/person/year, respectively, whereas An. pharoensis had an estimated outdoor EIR of 3.0 infective bites/person/year. In conclusion, An. arabiensis and An. pharoensis showed exophagic and zoophagic behavior. Human exposure to An. arabiensis bites occurred mostly indoors for LLIN non-users, while most of the exposure to both An. arabiensis and An. pharoensis bites occurred outdoors for LLIN users. Malaria transmission by An. arabiensis occurred both indoors and outdoors, whereas An. pharoensis contributed exclusively to outdoor transmission. Additional control tools targeting early-evening and outdoor biting malaria vectors are required to complement the current control interventions to control residual transmission and ultimately achieve malaria elimination.
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Soma DD, Zogo BM, Somé A, Tchiekoi BN, Hien DFDS, Pooda HS, Coulibaly S, Gnambani JE, Ouari A, Mouline K, Dahounto A, Ouédraogo GA, Fournet F, Koffi AA, Pennetier C, Moiroux N, Dabiré RK. Anopheles bionomics, insecticide resistance and malaria transmission in southwest Burkina Faso: A pre-intervention study. PLoS One 2020; 15:e0236920. [PMID: 32745085 PMCID: PMC7398507 DOI: 10.1371/journal.pone.0236920] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/17/2020] [Indexed: 11/21/2022] Open
Abstract
Background Twenty-seven villages were selected in southwest Burkina Faso to implement new vector control strategies in addition to long lasting insecticidal nets (LLINs) through a Randomized Controlled Trial (RCT). We conducted entomological surveys in the villages during the dry cold season (January 2017), dry hot season (March 2017) and rainy season (June 2017) to describe malaria vectors bionomics, insecticide resistance and transmission prior to this trial. Methods We carried out hourly catches (from 17:00 to 09:00) inside and outside 4 houses in each village using the Human Landing Catch technique. Mosquitoes were identified using morphological taxonomic keys. Specimens belonging to the Anopheles gambiae complex and Anopheles funestus group were identified using molecular techniques as well as detection of Plasmodium falciparum infection and insecticide resistance target-site mutations. Results Eight Anopheles species were detected in the area. Anopheles funestus s.s was the main vector during the dry cold season. It was replaced by Anopheles coluzzii during the dry hot season whereas An. coluzzii and An. gambiae s.s. were the dominant species during the rainy season. Species composition of the Anopheles population varied significantly among seasons. All insecticide resistance mechanisms (kdr-w, kdr-e and ace-1 target site mutations) investigated were found in each members of the An. gambiae complex but at different frequencies. We observed early and late biting phenotypes in the main malaria vector species. Entomological inoculation rates were 2.61, 2.67 and 11.25 infected bites per human per month during dry cold season, dry hot season and rainy season, respectively. Conclusion The entomological indicators of malaria transmission were high despite the universal coverage with LLINs. We detected early and late biting phenotypes in the main malaria vector species as well as physiological insecticide resistance mechanisms. These data will be used to evaluate the impact of complementary tools to LLINs in an upcoming RCT.
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Affiliation(s)
- Dieudonné Diloma Soma
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- Université Nazi Boni, Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- * E-mail:
| | - Barnabas Mahugnon Zogo
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
- Université d’Abomey Calavi, Abomey-Calavi, Benin
| | - Anthony Somé
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Bertin N’Cho Tchiekoi
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
| | | | - Hermann Sié Pooda
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- Université de Dédougou, Dédougou, Burkina Faso
| | - Sanata Coulibaly
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
| | | | - Ali Ouari
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
| | - Karine Mouline
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Amal Dahounto
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | | | - Florence Fournet
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | | | - Cédric Pennetier
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
- Institut Pierre Richet (IPR), Bouaké, Côte d’Ivoire
| | - Nicolas Moiroux
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
- MIVEGEC, Université de Montpellier, CNRS, IRD, Montpellier, France
| | - Roch Kounbobr Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS), Bobo-Dioulasso, Burkina Faso
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Araújo MDS, Andrade AO, Dos Santos NAC, Castro RB, Pereira DB, Rodrigues MMDS, Costa GDS, Júnior AMP, Carvalho LPC, de Medeiros JF, Pereira-da-Silva LH. First Observation of Experimental Plasmodium vivax Infection of Three Malaria Vectors from the Brazilian Amazon. Vector Borne Zoonotic Dis 2020; 20:517-523. [PMID: 32255759 DOI: 10.1089/vbz.2019.2527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Although malaria is endemic to the Amazon region, little is known about the susceptibility of potential parasite vectors in Brazil. Assessing the vector susceptibility of Anopheles mosquitoes will increase our understanding of parasite-vector interactions and aid the design of vector control strategies. This study assessed the susceptibility of three Anopheles species to midgut infection by Plasmodium vivax, the predominant malaria species in Rondônia State, Brazil. Blood from P. vivax infected patients was fed to Anopheles aquasalis, Anopheles darlingi, and Anopheles deaneorum mosquitoes using a membrane feeding assay (MFA). Gametocytemia was estimated by microscopic examination of blood smears and oocyst prevalence, and infection intensity was assessed. The presence of oocysts was determined by microscopy, and the infection rates and infection intensity were determined for all species. Data from six MFAs showed that An. darlingi and An. deaneorum exhibited the highest infection rates (97% and 90%, respectively) and developed a similar median number of P. vivax oocysts (142 and 123, respectively), while An. aquasalis exhibited the smallest infection rates (77%) and the median number of oocysts (88). Established laboratory colonies of An. darlingi and An. deaneorum and susceptibility to plasmodial infection would be beneficial for modeling P. vivax vector-parasite interactions in Brazil.
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Affiliation(s)
- Maisa da Silva Araújo
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Programa de Pós-Graduação em Biologia Experimental, Fundação Universidade Federal de Rondônia, Porto Velho, Rondônia, Brasil.,Instituto Nacional de Epidemiologia da Amazônia Ocidental-INCT/EpiAmo, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil
| | - Alice Oliveira Andrade
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Programa de Pós-Graduação em Biologia Experimental, Fundação Universidade Federal de Rondônia, Porto Velho, Rondônia, Brasil
| | - Najara Akira Costa Dos Santos
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Programa de Pós-Graduação em Biologia Experimental, Fundação Universidade Federal de Rondônia, Porto Velho, Rondônia, Brasil
| | - Raphael Brum Castro
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil
| | - Dhélio Batista Pereira
- Ambulatório de Malária, Centro de Pesquisa em Medicina Tropical, Porto Velho, Rondônia, Brasil
| | | | - Glaucilene da Silva Costa
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Programa de Pós-Graduação em Biologia Experimental, Fundação Universidade Federal de Rondônia, Porto Velho, Rondônia, Brasil
| | - Antonio Marques Pereira Júnior
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Instituto Nacional de Epidemiologia da Amazônia Ocidental-INCT/EpiAmo, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil
| | - Luís Paulo Costa Carvalho
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Programa de Pós-Graduação em Biologia Experimental, Fundação Universidade Federal de Rondônia, Porto Velho, Rondônia, Brasil
| | - Jansen Fernandes de Medeiros
- Laboratório de Entomologia, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil.,Instituto Nacional de Epidemiologia da Amazônia Ocidental-INCT/EpiAmo, Fundação Oswaldo Cruz-Fiocruz Rondônia, Porto Velho, Rondônia, Brasil
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Musiime AK, Smith DL, Kilama M, Rek J, Arinaitwe E, Nankabirwa JI, Kamya MR, Conrad MD, Dorsey G, Akol AM, Staedke SG, Lindsay SW, Egonyu JP. Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda. Malar J 2019; 18:445. [PMID: 31881898 PMCID: PMC6935116 DOI: 10.1186/s12936-019-3076-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 12/14/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared. METHODS The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR). RESULTS The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p < 0.001) and annual entomological inoculation rate from 129 to 0 infective bites per person per year (p < 0.001). The proportion of mosquitoes collected outdoors increased from 11.6 to 49.4% (p < 0.001). Prior to the interventions the predominant species was Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%). CONCLUSIONS Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.
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Affiliation(s)
- Alex K Musiime
- Infectious Diseases Research Collaboration, Kampala, Uganda. .,Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda.
| | - David L Smith
- Institute for Health Metrics & Evaluation, University of Washington, Seattle, WA, USA
| | - Maxwell Kilama
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - John Rek
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | - Joaniter I Nankabirwa
- Infectious Diseases Research Collaboration, Kampala, Uganda.,Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Moses R Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda.,Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - Melissa D Conrad
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Grant Dorsey
- Department of Medicine, University of California San Francisco, San Francisco, CA, USA
| | - Anne M Akol
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda
| | - Sarah G Staedke
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK
| | | | - James P Egonyu
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, Makerere University, Kampala, Uganda.,International Center of Insect Physiology and Ecology, Nairobi, Kenya
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9
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Seyfarth M, Khaireh BA, Abdi AA, Bouh SM, Faulde MK. Five years following first detection of Anopheles stephensi (Diptera: Culicidae) in Djibouti, Horn of Africa: populations established-malaria emerging. Parasitol Res 2019; 118:725-732. [PMID: 30671729 DOI: 10.1007/s00436-019-06213-0] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 01/10/2019] [Indexed: 12/24/2022]
Abstract
The Asian malaria mosquito, Anopheles stephensi, is a well-known and important vector of Plasmodium falciparum and P. vivax. Until 2013, its geographical distribution was confined to central and southern Asia including the Arabian Peninsula. In the Horn of Africa (HoA) Region, An. stephensi was first recorded from Djibouti in 2012, when it was linked geographically and temporally with an unusual outbreak of urban P. falciparum malaria. In 2016, An. stephensi was detected in the neighbouring Somali Region of Ethiopia. In order to determine whether An. stephensi populations have become established in Djibouti and contributed to the unusual rise in local malaria cases there, we carried out continuous vector surveillance from January 2013 to December 2017, investigated seasonal changes in An. stephensi population densities and bionomics, analysed available literature describing malaria in Djibouti since 2013, and investigated whether An. stephensi may have contributed to local malaria transmission by detecting circumsporozoite antigen of P. falciparum and P. vivax in female anophelines. From 2013 to 2016, seasonal activity of An. stephensi in urban Djibouti City primarily occurred during the colder, wetter season between September and May, with either no or rare trap catches from June to August. Unlike past years, this species was detected year-round, including the extremely hot summer months of June to August 2017. This change in seasonal occurrence may indicate that An. stephensi populations are adapting to their new environment in sub-Saharan Africa, facilitating their spread within Djibouti City. Among the 96 female An. stephensi investigated for malaria infectivity, three (3.1%) were positive for P. falciparum circumsporozoite antigen, including one P. falciparum/P. vivax VK 210 double infection. Subsequent to the unusual resurgence of local malaria in 2013, with 1684 confirmed cased reported for that year, malaria case numbers increased continuously, peaking at 14,810 in 2017. Prior to 2016, only P. falciparum malaria cases had been reported, but in 2016, autochthonously acquired P. vivax malaria cases occurred for the first time at a rate of 16.7% among all malaria cases recorded that year. This number increased to 36.7% in 2017. Our data indicate that the dynamics of malaria species in Djibouti is currently changing rapidly, and that An. stephensi can be involved in the transmission of both P. falciparum and P. vivax, simultaneously. Considering the extremely high potential impact of urban malaria on public health, the timely deployment of optimal multinational vector surveillance and control programs against An. stephensi is strongly recommended, not only for the HoA Region, but for the entire African continent.
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Affiliation(s)
- Marco Seyfarth
- Bundeswehr Medical Office, Office of the Surgeon General, Koblenz, Germany
| | - Bouh A Khaireh
- Solidaris Health, Public Health and Development Research Center, 10 Boulevard de la République, BP 1000, Djibouti, Republic of Djibouti.,Department of Microbiology, Faculty of Medicine, University of Djibouti, BP 1906, 12 Rue de l'École de Médecine, Djibouti, Republic of Djibouti
| | - Abdoulilah A Abdi
- President Health Advisor, Cabinet of the President, Republic of Djibouti and Directorate, Djiboutian Armed Forces Health Service, Djibouti City, Republic of Djibouti
| | - Samatar M Bouh
- Director Health Information System, Ministry of Health, Djibouti City, Republic of Djibouti
| | - Michael K Faulde
- Department XXI B, Section Medical Entomology/Zoology, Bundeswehr Central Hospital, PO Box 7460, D-56064, Koblenz, Germany. .,Institute of Medical Microbiology, Immunology and Parasitology, University Clinics Bonn, 53105, Bonn, Germany.
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10
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Stevenson JC, Norris DE. Implicating Cryptic and Novel Anophelines as Malaria Vectors in Africa. INSECTS 2016; 8:E1. [PMID: 28025486 PMCID: PMC5371929 DOI: 10.3390/insects8010001] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 12/09/2016] [Accepted: 12/12/2016] [Indexed: 11/24/2022]
Abstract
Entomological indices and bionomic descriptions of malaria vectors are essential to accurately describe and understand malaria transmission and for the design and evaluation of appropriate control interventions. In order to correctly assign spatio-temporal distributions, behaviors and responses to interventions to particular anopheline species, identification of mosquitoes must be accurately made. This paper reviews the current methods and their limitations in correctly identifying anopheline mosquitoes in sub-Saharan Africa, and highlights the importance of molecular methods to discriminate cryptic species and identify lesser known anophelines. The increasing number of reports of Plasmodium infections in assumed "minor", non-vector, and cryptic and novel species is reviewed. Their importance in terms of evading current control and elimination strategies and therefore maintaining malaria transmission is emphasized.
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Affiliation(s)
- Jennifer C Stevenson
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
- Macha Research Trust, Choma P.O. Box 630166, Southern Province, Zambia.
| | - Douglas E Norris
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
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