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Kanatani S, Stiffler D, Bousema T, Yenokyan G, Sinnis P. Revisiting the Plasmodium sporozoite inoculum and elucidating the efficiency with which malaria parasites progress through the mosquito. Nat Commun 2024; 15:748. [PMID: 38272943 PMCID: PMC10811227 DOI: 10.1038/s41467-024-44962-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 01/05/2024] [Indexed: 01/27/2024] Open
Abstract
Malaria is initiated when infected anopheline mosquitoes inoculate sporozoites as they probe for blood. It is thought that all infected mosquitoes are equivalent in terms of their infectious potential, with parasite burden having no role in transmission success. In this study, using mosquitoes harboring the entire range of salivary gland sporozoite loads observed in the field, we demonstrate a strong and highly significant correlation between mosquito parasite burden and inoculum size. We then link the inoculum data to oocyst counts, the most commonly-used metric to assess mosquito infection in the field, and determine the efficiency with which oocyst sporozoites enter mosquito salivary glands. Taken together our data support the conclusion that mosquitoes with higher parasite burdens are more likely to initiate infection and contribute to onward transmission. Overall these data may account for some of the unexplained heterogeneity in transmission and enable more precise benchmarks for transmission-blocking interventions.
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Affiliation(s)
- Sachie Kanatani
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
- Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Deborah Stiffler
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Teun Bousema
- Department of Medical Microbiology & Radboud Center for Infectious Diseases, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Gayane Yenokyan
- Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Photini Sinnis
- Department of Molecular Microbiology & Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
- Johns Hopkins Malaria Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
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2
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Thabet HS, TagEldin RA, Fahmy NT, Diclaro JW, Alaribe AA, Ezedinachi E, Nwachuku NS, Odey FO, Arimoto H. Spatial Distribution of PCR-Identified Species of Anopheles gambiae senu lato (Diptera: Culicidae) Across Three Eco-Vegetational Zones in Cross River State, Nigeria. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:576-584. [PMID: 35064267 DOI: 10.1093/jme/tjab221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Indexed: 06/14/2023]
Abstract
Anopheles gambiae sensu lato complex (An. gambiae s.l.) describes a group of nine morphologically indistinguishable members that vary in their distribution, ability to transmit malaria, and susceptibility to pyrethroids. Here, we recorded the spatial patterns of PCR-identified An. gambiae s.l. complex species collected from four sites in Cross River State, Nigeria that represented three different ecological zones. Trapping was conducted between October 2015 and June 2016. Anopheles gambiae s.l. complex species identification was performed using species-specific primers followed by An. gambiae and An. coluzzii differentiation using the restriction fragment length polymorphism (RFLP) method. Bivariate and multivariate logistic regression models were used to identify ecological and seasonal variables closely associated with An. coluzzii and An. gambiae distribution. Out of 1,388 An. gambiae s.l. successfully amplified, 1,074 (77.4%) were An. coluzzii, 278 (20%) were An. gambiae, and 25 (1.8%) were hybrids (An. coluzzii/An. gambiae). A very small number of An. arabiensis (0.8%, n = 11) were also collected. Statistical analysis indicated that An. coluzzii is predominant in Guinea-savannah and tropical rainforest, and is highly associated with rainy seasons, while, An. gambiae is prevalent in mangrove swamp forest during dry seasons. Only 13 An. gambiae s.l. females were infected with Plasmodium falciparum (P. falciparum). The sporozoite infection rate was higher in mangrove swamp forest (53.8%, n = 7) than in rain forest (38.5%, n = 5) followed by Guinea-savannah (7.7%, n = 1) ecological zones. These results provide important insights for strategic planning of malaria control programs in Nigeria.
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Affiliation(s)
- H S Thabet
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - R A TagEldin
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - N T Fahmy
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - J W Diclaro
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
- Navy Entomology Center of Excellence (NECE), Jacksonville, FL, USA
| | - A A Alaribe
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - E Ezedinachi
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - N S Nwachuku
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - F O Odey
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - H Arimoto
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
- Navy Environmental and Preventive Medicine Unit Five, San Diego, CA, USA
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Tarimo BB, Nyasembe VO, Ngasala B, Basham C, Rutagi IJ, Muller M, Chhetri SB, Rubinstein R, Juliano JJ, Loya M, Dinglasan RR, Lin JT, Mathias DK. Seasonality and transmissibility of Plasmodium ovale in Bagamoyo District, Tanzania. Parasit Vectors 2022; 15:56. [PMID: 35164867 PMCID: PMC8842944 DOI: 10.1186/s13071-022-05181-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 12/12/2021] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Plasmodium ovale is a neglected malarial parasite that can form latent hypnozoites in the human liver. Over the last decade, molecular surveillance studies of non-falciparum malaria in Africa have highlighted that P. ovale is circulating below the radar, including areas where Plasmodium falciparum is in decline. To eliminate malaria where P. ovale is endemic, a better understanding of its epidemiology, asymptomatic carriage, and transmission biology is needed. METHODS We performed a pilot study on P. ovale transmission as part of an ongoing study of human-to-mosquito transmission of P. falciparum from asymptomatic carriers. To characterize the malaria asymptomatic reservoir, cross-sectional qPCR surveys were conducted in Bagamoyo, Tanzania, over three transmission seasons. Positive individuals were enrolled in transmission studies of P. falciparum using direct skin feeding assays (DFAs) with Anopheles gambiae s.s. (IFAKARA strain) mosquitoes. For a subset of participants who screened positive for P. ovale on the day of DFA, we incubated blood-fed mosquitoes for 14 days to assess sporozoite development. RESULTS Molecular surveillance of asymptomatic individuals revealed a P. ovale prevalence of 11% (300/2718), compared to 29% (780/2718) for P. falciparum. Prevalence for P. ovale was highest at the beginning of the long rainy season (15.5%, 128/826) in contrast to P. falciparum, which peaked later in both the long and short rainy seasons. Considering that these early-season P. ovale infections were low-density mono-infections (127/128), we speculate many were due to hypnozoite-induced relapse. Six of eight P. ovale-infected asymptomatic individuals who underwent DFAs successfully transmitted P. ovale parasites to A. gambiae. CONCLUSIONS Plasmodium ovale is circulating at 4-15% prevalence among asymptomatic individuals in coastal Tanzania, largely invisible to field diagnostics. A different seasonal peak from co-endemic P. falciparum, the capacity to relapse, and efficient transmission to Anopheles vectors likely contribute to its persistence amid control efforts focused on P. falciparum.
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Affiliation(s)
- Brian B. Tarimo
- Vector Immunity and Transmission Biology Unit, Department of Environmental Health and Ecological Science, Ifakara Health Institute-Bagamoyo Office, P.O. Box 74, Bagamoyo, Coast Region 61301 Tanzania
| | - Vincent O. Nyasembe
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611 USA
| | - Billy Ngasala
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, Dar es Salaam, 11103 Tanzania
| | - Christopher Basham
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Isaack J. Rutagi
- Vector Immunity and Transmission Biology Unit, Department of Environmental Health and Ecological Science, Ifakara Health Institute-Bagamoyo Office, P.O. Box 74, Bagamoyo, Coast Region 61301 Tanzania
| | - Meredith Muller
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Srijana B. Chhetri
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Rebecca Rubinstein
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Jonathan J. Juliano
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Mwajabu Loya
- Department of Parasitology and Medical Entomology, School of Public Health and Social Sciences, Muhimbili University of Health and Allied Sciences, Dar es Salaam, 11103 Tanzania
| | - Rhoel R. Dinglasan
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611 USA
| | - Jessica T. Lin
- Institute of Global Health and Infectious Diseases, University of North Carolina School of Medicine, Chapel Hill, NC 27599 USA
| | - Derrick K. Mathias
- Department of Entomology and Nematology, Florida Medical Entomology Laboratory, Institute of Food and Agricultural Sciences, University of Florida, Vero Beach, FL 32962 USA
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Onen H, Odong R, Chemurot M, Tripet F, Kayondo JK. Predatory and competitive interaction in Anopheles gambiae sensu lato larval breeding habitats in selected villages of central Uganda. Parasit Vectors 2021; 14:420. [PMID: 34419140 PMCID: PMC8380324 DOI: 10.1186/s13071-021-04926-9] [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: 03/23/2021] [Accepted: 08/04/2021] [Indexed: 11/10/2022] Open
Abstract
Background Malaria is often persistent in communities surrounded by mosquito breeding habitats. Anopheles gambiae sensu lato exploit a variety of aquatic habitats, but the biotic determinants of its preferences are poorly understood. This study aimed to identify and quantify macroinvertebrates in different habitat types with determined water physico-chemical parameters to establish those preferred by An. gambiae s.l. larvae as well as their predators and competitors. Methods A field survey was conducted in Kibuye and Kayonjo villages located in the vicinity of the River Sezibwa, north-eastern Uganda to identify Anopheline larval habitats shared by aquatic insects. Habitats were geo-recorded and as streams, ponds, temporary pools and roadside ditches. From October to December 2017, random microhabitats/quadrats were selected from each habitat type, their water physico-chemical parameters (electrical conductivity, total dissolved solids, temperature and pH) were measured, and they were sampled for macroinvertebrates using standard dippers. All collected arthropod macroinvertebrates were then morphologically identified to family level and enumerated. Results Principal component analysis showed that the four larval habitat types were characterized by distinct physico-chemical parameter profiles. Ponds and streams had the highest number and diversity of macroinvertebrate insect taxa and sustained few An. gambiae s.l. larvae. Anopheles gambiae s.l. were more common in roadside ditches and particularly abundant in temporary pools which it commonly shared with Dytiscidae (predaceous diving beetles) and Culex spp. Cluster correlation analysis conducted on the abundance of these taxa within quadrats suggested that An. gambiae s.l. and Dytiscidae have the most similar patterns of microhabitat use, followed by Cybaeidae (water spiders). Whilst Culex spp. co-occurred with An. gambiae s.l. in some habitats, there was only partial niche overlap and no clear evidence of competition between the two mosquito taxa. Conclusions Ponds and streams are habitats that host the largest diversity and abundance of aquatic insect taxa. Anopheles gambiae s.l. larvae distinctively preferred temporary pools and roadside ditches, where they were exposed to few predators and no apparent competition by Culex spp. Further studies should aim to test the impact of Dytiscidae and Cybaeidae on An. gambiae s.l. dynamics experimentally. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-021-04926-9.
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Affiliation(s)
- Hudson Onen
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, School of Biosciences, Makerere University, PO Box 7062, Kampala, Uganda. .,Department of Entomology, Uganda Virus Research Institute (UVRI), PO Box 49, Entebbe, Uganda. .,Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, SFD, ST5 5BG, UK.
| | - Robinson Odong
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, School of Biosciences, Makerere University, PO Box 7062, Kampala, Uganda
| | - Moses Chemurot
- Department of Zoology, Entomology and Fisheries Sciences, College of Natural Sciences, School of Biosciences, Makerere University, PO Box 7062, Kampala, Uganda
| | - Frédéric Tripet
- Centre for Applied Entomology and Parasitology, School of Life Sciences, Keele University, Keele, SFD, ST5 5BG, UK.
| | - Jonathan K Kayondo
- Department of Entomology, Uganda Virus Research Institute (UVRI), PO Box 49, Entebbe, Uganda
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Ghassemi-Khademi T, Oshaghi MA, Vatandoost H, Madjdzadeh SM, Gorouhi MA. Utility of Complete Mitochondrial Genomes in Phylogenetic Classification of the Species of Anopheles (Culicidae: Anophelinae). J Arthropod Borne Dis 2021; 15:1-20. [PMID: 34277853 PMCID: PMC8271240 DOI: 10.18502/jad.v15i1.6483] [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: 12/30/2019] [Accepted: 03/30/2021] [Indexed: 11/24/2022] Open
Abstract
Background: Among the blood-sucking insects, Anopheles mosquitoes have a very special position, because they transmit parasites of the genus Plasmodium, which cause malaria as one of the main vector-borne disease worldwide. The aim of this review study was to evaluate utility of complete mitochondrial genomes in phylogenetic classification of the species of Anopheles. Methods: The complete mitochondrial genome sequences belonging to 28 species of the genus Anopheles (n=32) were downloaded from NCBI. The phylogenetic trees were constructed using the ML, NJ, ME, and Bayesian inference methods. Results: In general, the results of the present survey revealed that the complete mitochondrial genomes act very accurately in recognition of the taxonomic and phylogenetic status of these species and provide a higher level of support than those based on individual or partial mitochondrial genes so that by using them, we can meticulously reconstruct and modify Anopheles classification. Conclusion: Understanding the taxonomic position of Anopheles, can be a very effective step in better planning for controlling these malaria vectors in the world and will improve our knowledge of their evolutionary biology.
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Affiliation(s)
| | - Mohammad Ali Oshaghi
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Hassan Vatandoost
- Department of Medical Entomology and Vector Control, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.,Department of Chemical Pollutants and Pesticides, Institute for Environmental Research, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Mohammad Amin Gorouhi
- Department of Vector Biology and Control, School of Public Health, Kerman University of Medical Sciences, Kerman, Iran.,Research Center of Tropical and Infectious Diseases Kerman University of Medical Sciences, Kerman, Iran
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Eba K, Habtewold T, Yewhalaw D, Christophides GK, Duchateau L. Anopheles arabiensis hotspots along intermittent rivers drive malaria dynamics in semi-arid areas of Central Ethiopia. Malar J 2021; 20:154. [PMID: 33731115 PMCID: PMC7971958 DOI: 10.1186/s12936-021-03697-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/11/2021] [Indexed: 11/30/2022] Open
Abstract
Background Understanding malaria vector’s population dynamics and their spatial distribution is important to define when and where the largest infection risks occur and implement appropriate control strategies. In this study, the seasonal spatio-temporal dynamics of the malaria vector population and transmission intensity along intermittent rivers in a semi-arid area of central Ethiopia were investigated. Methods Mosquitoes were collected monthly from five clusters, 2 close to a river and 3 away from a river, using pyrethrum spray catches from November 2014 to July 2016. Mosquito abundance was analysed by the mixed Poisson regression model. The human blood index and sporozoite rate was compared between seasons by a logistic regression model. Results A total of 2784 adult female Anopheles gambiae sensu lato (s.l.) were collected during the data collection period. All tested mosquitoes (n = 696) were identified as Anopheles arabiensis by polymerase chain reaction. The average daily household count was significantly higher (P = 0.037) in the clusters close to the river at 5.35 (95% CI 2.41–11.85) compared to the clusters away from the river at 0.033 (95% CI 0.02–0.05). Comparing the effect of vicinity of the river by season, a significant effect of closeness to the river was found during the dry season (P = 0.027) and transition from dry to wet season (P = 0.032). Overall, An. arabiensis had higher bovine blood index (62.8%) as compared to human blood index (23.8%), ovine blood index (9.2%) and canine blood index (0.1%). The overall sporozoite rate was 3.9% and 0% for clusters close to and away from the river, respectively. The overall Plasmodium falciparum and Plasmodium vivax entomologic inoculation rates for An. arabiensis in clusters close to the river were 0.8 and 2.2 infective bites per person/year, respectively. Conclusion Mosquito abundance and malaria transmission intensity in clusters close to the river were higher which could be attributed to the riverine breeding sites. Thus, vector control interventions including targeted larval source management should be implemented to reduce the risk of malaria infection in the area. Supplementary Information The online version contains supplementary material available at 10.1186/s12936-021-03697-z.
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Affiliation(s)
- Kasahun Eba
- Biometrics Research Centre, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.,Department of Environmental Health Science and Technology, Jimma University, P.O. Box 378, Jimma, Ethiopia
| | - Tibebu Habtewold
- Department of Life Sciences, Imperial College London, London, UK
| | - Delenasaw Yewhalaw
- School of Medical Laboratory Sciences, Jimma University, P.O.Box 378, Jimma, Ethiopia.,Tropical and Infectious Diseases Research Center, Jimma University, P.O.Box 378, Jimma, Ethiopia
| | | | - Luc Duchateau
- Biometrics Research Centre, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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Bartilol B, Omedo I, Mbogo C, Mwangangi J, Rono MK. Bionomics and ecology of Anopheles merus along the East and Southern Africa coast. Parasit Vectors 2021; 14:84. [PMID: 33509262 PMCID: PMC7842043 DOI: 10.1186/s13071-021-04582-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 01/05/2021] [Indexed: 11/25/2022] Open
Abstract
Malaria transmission persists despite the scale-up of interventions such as long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). Understanding the entomological drivers of transmission is key for the design of effective and sustainable tools to address the challenge. Recent research findings indicate a shift in vector populations from the notorious Anopheles gambiae (s.s.) as a dominant vector to other species as one of the factors contributing to the persistence of malaria transmission. However, there are gaps in the literature regarding the minor vector species which are increasingly taking a lead role in malaria transmission. Currently, minor malaria vectors have behavioural plasticity, which allows their evasion of vector control tools currently in use. To address this, we have reviewed the role of Anopheles merus, a saltwater mosquito species that is becoming an important vector of malaria transmission along the East and Southern African coast. We performed a literature review from PubMed and Google Scholar and reviewed over 50 publications relating to An. merus's bionomics, taxonomy, spatial-temporal distribution and role in malaria transmission. We found that An. merus is an important vector of malaria and that it contributes to residual malaria transmission because of its exophilic tendencies, insecticide resistance and densities that peak during the dry seasons as the freshwater mosquitoes decline. Spatial and temporal studies have also shown that this species has increased its geographical range, densities and vectorial capacity over time. In this review, we highlight the resting behaviour and breeding habitats of this mosquito, which could be targeted for surveillance studies and control interventions.
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Affiliation(s)
- Brian Bartilol
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.
- Pwani University Bioscience Research Centre (PUBReC), Pwani University, Kilifi, Kenya.
| | - Irene Omedo
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- Big Data Institute, University of Oxford, Oxford, UK
| | - Charles Mbogo
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
| | - Joseph Mwangangi
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya
- Kenya Medical Research Institute, Centre for Vector Disease Control, Kwale, Kenya
| | - Martin K Rono
- Kenya Medical Research Institute, Centre for Geographic Medicine Research-Coast, Kilifi, Kenya.
- Pwani University Bioscience Research Centre (PUBReC), Pwani University, Kilifi, Kenya.
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Braack L, Bornman R, Kruger T, Dahan-Moss Y, Gilbert A, Kaiser M, Oliver SV, Cornel AJ, Lee Y, Norris DE, Coetzee M, Brooke B, de Jager C. Malaria Vectors and Vector Surveillance in Limpopo Province (South Africa): 1927 to 2018. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17114125. [PMID: 32527067 PMCID: PMC7313001 DOI: 10.3390/ijerph17114125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/05/2020] [Accepted: 06/06/2020] [Indexed: 11/16/2022]
Abstract
Despite the annual implementation of a robust and extensive indoor residual spraying programme against malaria vectors in Limpopo Province (South Africa), significant transmission continues and is a serious impediment to South Africa’s malaria elimination objectives. In order to gain a better understanding regarding possible causes of this residual malaria, we conducted a literature review of the historical species composition and abundance of malaria vector mosquitoes in the Limpopo River Valley region of the Vhembe District, northern Limpopo Province, the region with the highest remaining annual malaria cases in South Africa. In addition, mosquito surveys were carried out in the same region between October 2017 and October 2018. A total of 2225 adult mosquitoes were collected using CO2-baited tent and light traps, human landing catches and cow-baited traps. Of the 1443 Anopheles collected, 516 were members of the An. gambiae complex and 511 An. funestus group. In the malaria endemic rural areas outside the Kruger National Park, one specimen each of An. gambiae s.s. and An. funestus and only three of An. arabiensis were collected. The latter species was abundant at a remote hot spring in the neighboring Kruger National Park. Eighteen other species of Anopheles were collected. Our survey results support the historical findings that An. arabiensis, the species widely held to be the prime malaria vector in South Africa, is a rare species in the malaria endemic Limpopo River Valley. The implications of the mosquito surveys for malaria transmission, elimination and vector control in northern Limpopo Province and neighboring regions are discussed.
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Affiliation(s)
- Leo Braack
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
- Correspondence:
| | - Riana Bornman
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
| | - Taneshka Kruger
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
| | - Yael Dahan-Moss
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Allison Gilbert
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Maria Kaiser
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Shüné V. Oliver
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Anthony J. Cornel
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
- Department of Entomology & Nematology, University of California, Davis, CA 95616, USA;
| | - Yoosook Lee
- Department of Entomology & Nematology, University of California, Davis, CA 95616, USA;
| | - Douglas E. Norris
- The W Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA;
| | - Maureen Coetzee
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Basil Brooke
- Vector Control Reference Laboratory, Centre for Emerging, Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg2001, South Africa; (Y.D.-M.); (A.G.); (M.K.); (S.V.O.); (M.C.); (B.B.)
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2001, South Africa
| | - Christiaan de Jager
- University of Pretoria Institute for Sustainable Malaria Control, School of Health Systems and Public Health, Faculty of Health Sciences, University of Pretoria, Pretoria 0028, South Africa; (R.B.); (T.K.); (A.J.C.); (C.d.J.)
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Aleshnick M, Ganusov VV, Nasir G, Yenokyan G, Sinnis P. Experimental determination of the force of malaria infection reveals a non-linear relationship to mosquito sporozoite loads. PLoS Pathog 2020; 16:e1008181. [PMID: 32453765 PMCID: PMC7295235 DOI: 10.1371/journal.ppat.1008181] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 06/15/2020] [Accepted: 04/04/2020] [Indexed: 11/30/2022] Open
Abstract
Plasmodium sporozoites are the infective stage of the malaria parasite. Though this is a bottleneck for the parasite, the quantitative dynamics of transmission, from mosquito inoculation of sporozoites to patent blood-stage infection in the mammalian host, are poorly understood. Here we utilize a rodent model to determine the probability of malaria infection after infectious mosquito bite, and consider the impact of mosquito parasite load, blood-meal acquisition, probe-time, and probe location, on infection probability. We found that infection likelihood correlates with mosquito sporozoite load and, to a lesser degree, the duration of probing, and is not dependent upon the mosquito’s ability to find blood. The relationship between sporozoite load and infection probability is non-linear and can be described by a set of models that include a threshold, with mosquitoes harboring over 10,000 salivary gland sporozoites being significantly more likely to initiate a malaria infection. Overall, our data suggest that the small subset of highly infected mosquitoes may contribute disproportionally to malaria transmission in the field and that quantifying mosquito sporozoite loads could aid in predicting the force of infection in different transmission settings. Malaria is a leading cause of death in many parts of the world. Infection is initiated when infected Anopheles mosquitoes inject sporozoites as they look for blood. Though transmission is a bottleneck for the parasite and thus a good point for intervention, many aspects of transmission remain poorly understood. In this study, using a rodent model of malaria, we found that the majority of infective bites do not result in malaria infection. Furthermore, we found that the bites of mosquitoes with heavy parasite burdens are significantly more likely to result in blood stage infection. These data have important implications for designing interventions targeting transmission stages of the malaria parasite as they suggest that reducing parasite loads, even without completely eliminating them, could be effective against disease spread. We also found that mosquitoes that probe but do not succeed in finding blood are equally likely to initiate infection, an important finding for human vaccine trials. Overall this work contributes to our understanding of the epidemiology of malaria and should aid in the development of malaria elimination strategies.
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Affiliation(s)
- Maya Aleshnick
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
| | - Vitaly V. Ganusov
- Departments of Microbiology and Mathematics, University of Tennessee, Knoxville Tennessee, United States of America
| | - Gibran Nasir
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
| | - Gayane Yenokyan
- Johns Hopkins Biostatistics Center, Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Photini Sinnis
- Johns Hopkins Malaria Research Institute and Department of Molecular Microbiology & Immunology, Baltimore, Maryland, United States of America
- * E-mail:
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10
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Kweka EJ, Mazigo HD, Lyaruu LJ, Mausa EA, Venter N, Mahande AM, Coetzee M. Anopheline Mosquito Species Composition, Kdr Mutation Frequency, and Parasite Infectivity Status in Northern Tanzania. JOURNAL OF MEDICAL ENTOMOLOGY 2020; 57:933-938. [PMID: 31923308 DOI: 10.1093/jme/tjz245] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Indexed: 06/10/2023]
Abstract
The scaling-up of malaria control interventions in northern Tanzania has resulted in a decline in malaria prevalence and vector species composition. Despite this achievement, residual malaria transmission remains a concern in the area. The main aim of this study was to investigate malaria vector species composition, parasite infectivity rates, and the presence of insecticide knockdown resistance (kdr) mutations in three sites that have experienced a significant decline in malaria in northern Tanzania. Adult mosquitoes were sampled using light traps in houses and hand-aspirators in cowsheds, whereas the standard dipping method was used for sampling mosquito larvae. Adult mosquitoes identified as Anopheles gambiae s.l. and An. funestus s.l. and larval stages III and IV of An. gambiae s.l. were stored in absolute ethanol for further laboratory molecular identification. The identified species in the An. gambiae complex were An. gambiae s.s., An. merus, An. quadriannulatus, and An. arabiensis, whereas the An. funestus group comprised An. funestus s.s., An. rivulorum, and An. leesoni. For An. gambiae s.s. analyzed from Zeneth, 47.6% were kdr-East homozygous susceptible, 35.7% kdr-East heterozygous resistant, 9.6% kdr-East homozygous resistant, and 7.1% undefined, whereas specimens from Kwakibuyu were 45.5% kdr-East homozygous susceptible, 32.7% kdr-East heterozygous resistant, 16.3% kdr-East homozygous resistant, and 5.5% undefined. There were no kdr-West alleles identified from any specimen. The overall malaria parasite infectivity rate was 0.75%. No infections were found in Moshi. The findings indicate that populations of the major malaria vector mosquitoes are still present in the study area, with An. funestus taking a lead in malaria transmission.
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Affiliation(s)
- Eliningaya J Kweka
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
- Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - Humphrey D Mazigo
- Department of Medical Parasitology and Entomology, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - Lucile J Lyaruu
- Division of Livestock and Human Diseases Vector Control, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - Emmanuel A Mausa
- National Plant Genetic Resource Centre, Tropical Pesticides Research Institute, Arusha, Tanzania
| | - Nelius Venter
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multi-disciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - Aneth M Mahande
- Mabogini Field Station, Tropical Pesticides Research Institute, Moshi, Tanzania
| | - Maureen Coetzee
- Wits Research Institute for Malaria and Wits/MRC Collaborating Centre for Multi-disciplinary Research on Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
- Centre for Emerging, Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
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11
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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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12
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Chinula D, Hamainza B, Chizema E, Kavishe DR, Sikaala CH, Killeen GF. Proportional decline of Anopheles quadriannulatus and increased contribution of An. arabiensis to the An. gambiae complex following introduction of indoor residual spraying with pirimiphos-methyl: an observational, retrospective secondary analysis of pre-existing data from south-east Zambia. Parasit Vectors 2018; 11:544. [PMID: 30305147 PMCID: PMC6180389 DOI: 10.1186/s13071-018-3121-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 09/19/2018] [Indexed: 12/21/2022] Open
Abstract
Background Across most of sub-Saharan Africa, malaria is transmitted by mosquitoes from the Anopheles gambiae complex, comprising seven morphologically indistinguishable but behaviourally-diverse sibling species with ecologically-distinct environmental niches. Anopheles gambiae and An. arabiensis are the mostly widely distributed major malaria vectors within the complex, while An. quadriannulatus is sparsely distributed. Methods Indoor residual spraying (IRS) with the organophosphate pirimiphos-methyl (PM) was conducted four times between 2011 and 2017 in the Luangwa Valley, south-east Zambia. Anopheles mosquitoes were repeatedly collected indoors by several experiments with various objectives conducted in this study area from 2010 onwards. Indoor mosquito collection methods included human landing catches, Centres for Disease Control and Prevention miniature light traps and back pack aspirators. Anopheles gambiae complex mosquitoes were morphologically identified to species level using taxonomic keys, and to molecular level by polymerase chain reaction. These multi-study data were collated so that time trends in the species composition of this complex could be assessed. Results The proportion of indoor An. gambiae complex accounted for by An. quadriannulatus declined from 95.1% to 69.7% following two application PM-IRS rounds with an emulsifiable concentrate formulation from 2011 to 2013, while insecticidal net utilisation remained consistently high throughout that period. This trend continued after two further rounds of PM-IRS with a longer-lasting capsule suspension formulation in 2015 and 2016/2017, following which An. quadriannulatus accounted for only 4.5% of the complex. During the same time interval there was a correspondingly steady rise in the proportional contribution of An. arabiensis to the complex, from 3.9 to 95.1%, while the contribution of nominate An. gambiae remained stable at ≤ 0.9%. Conclusion It seems likely that An. arabiensis is not only more behaviourally resilient against IRS than An. gambiae, but also than An. quadriannulatus populations exhibiting indoor-feeding, human-feeding and nocturnal behaviours that are unusual for this species. Routine, programmatic entomological monitoring of dynamic vector population guilds will be critical to guide effective selection and deployment of vector control interventions, including supplementary measures to tackle persisting vectors of residual malaria transmission like An. arabiensis.
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Affiliation(s)
- Dingani Chinula
- National Malaria Elimination Centre, Chainama Hills Hospital Grounds, PO Box 32509, Lusaka, Zambia. .,Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L35QA, United Kingdom.
| | - Busiku Hamainza
- National Malaria Elimination Centre, Chainama Hills Hospital Grounds, PO Box 32509, Lusaka, Zambia
| | - Elizabeth Chizema
- National Malaria Elimination Centre, Chainama Hills Hospital Grounds, PO Box 32509, Lusaka, Zambia
| | - Deogratius R Kavishe
- Ifakara Health Institute, Kiko Avenue, Environmental Health and Ecological Sciences Department, PO Box 53, Ifakara, United Republic of Tanzania
| | - Chadwick H Sikaala
- National Malaria Elimination Centre, Chainama Hills Hospital Grounds, PO Box 32509, Lusaka, Zambia
| | - Gerry F Killeen
- Liverpool School of Tropical Medicine, Vector Biology Department, Pembroke Place, Liverpool, L35QA, United Kingdom.,Ifakara Health Institute, Kiko Avenue, Environmental Health and Ecological Sciences Department, PO Box 53, Ifakara, United Republic of Tanzania
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13
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Mbokazi F, Coetzee M, Brooke B, Govere J, Reid A, Owiti P, Kosgei R, Zhou S, Magagula R, Kok G, Namboze J, Tweya H, Mabuza A. Changing distribution and abundance of the malaria vector Anopheles merus in Mpumalanga Province, South Africa. Public Health Action 2018; 8:S39-S43. [PMID: 29713593 DOI: 10.5588/pha.17.0034] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 12/10/2017] [Indexed: 11/10/2022] Open
Abstract
Background: The malaria vector Anopheles merus occurs in the Mpumalanga Province of South Africa. As its contribution to malaria transmission in South Africa has yet to be ascertained, an intensification of surveillance is necessary to provide baseline information on this species. The aim of this study was therefore to map An. merus breeding sites in the Ehlanzeni District of Mpumalanga Province and to assess qualitative trends in the distribution and relative abundance of this species over a 9-year period. Methods: The study was carried out during the period 2005-2014 in the four high-risk municipalities of Ehlanzeni District. Fifty-two breeding sites were chosen from all water bodies that produced anopheline mosquitoes. The study data were extracted from historical entomological records that are captured monthly. Results: Of the 15 058 Anopheles mosquitoes collected, 64% were An. merus. The abundance and distribution of An. merus increased throughout the four municipalities in Ehlanzeni District during the study period. Conclusion: The expanded distribution and increased abundance of An. merus in the Ehlanzeni District may contribute significantly to locally acquired malaria in Mpumalanga Province, likely necessitating the incorporation of additional vector control methods specifically directed against populations of this species.
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Affiliation(s)
- F Mbokazi
- Malaria Elimination Programme, Mpumalanga Department of Health, Ehlanzeni District, Mpumalanga, South Africa
| | - M Coetzee
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Vector Control Reference Laboratory, Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - B Brooke
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.,Vector Control Reference Laboratory, Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, Johannesburg, South Africa
| | - J Govere
- Wits Research Institute for Malaria, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - A Reid
- Operational Research Unit, Operational Centre Brussels, Medécins Sans Frontières, Luxembourg
| | - P Owiti
- Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya
| | - R Kosgei
- Department of Obstetrics and Gynaecology, University of Nairobi, Nairobi, Kenya
| | - S Zhou
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China
| | - R Magagula
- Malaria Elimination Programme, Mpumalanga Department of Health, Ehlanzeni District, Mpumalanga, South Africa
| | - G Kok
- Malaria Elimination Programme, Mpumalanga Department of Health, Ehlanzeni District, Mpumalanga, South Africa
| | - J Namboze
- World Health Organization, Regional Office for Africa Region, Asmara, Eritrea
| | - H Tweya
- The Lighthouse Trust, Lilongwe, Malawi
| | - A Mabuza
- Malaria Elimination Programme, Mpumalanga Department of Health, Ehlanzeni District, Mpumalanga, South Africa
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14
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Mwaiswelo R, Ngasala B, Gil JP, Malmberg M, Jovel I, Xu W, Premji Z, Mmbando BP, Björkman A, Mårtensson A. Sustained High Cure Rate of Artemether-Lumefantrine against Uncomplicated Plasmodium falciparum Malaria after 8 Years of Its Wide-Scale Use in Bagamoyo District, Tanzania. Am J Trop Med Hyg 2017; 97:526-532. [PMID: 28829723 DOI: 10.4269/ajtmh.16-0780] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
We assessed the temporal trend of artemether-lumefantrine (AL) cure rate after 8 years of its wide-scale use for treatment of uncomplicated Plasmodium falciparum malaria from 2006 to 2014 in Bagamoyo district, Tanzania. Trend analysis was performed for four studies conducted in 2006, 2007-2008, 2012-2013, and 2014. Patients with acute uncomplicated P. falciparum malaria were enrolled, treated with standard AL regimen and followed-up for 3 (2006), 28 (2014), 42 (2012-2013), or 56 (2007-2008) days for clinical and laboratory evaluation. Primary outcome was day 28 polymerase chain reaction (PCR)-adjusted cure rate across years from 2007 to 2014. Parasite clearance was slower for the 2006 and 2007-2008 cohorts with less than 50% of patients cleared of parasitemia on day 1, but was rapid for the 2012-2013 and 2014 cohorts. Day 28 PCR-adjusted cure rate was 168/170 (98.8%) (95% confidence interval [CI], 97.2-100), 122/127 (96.1%) (95% CI, 92.6-99.5), and 206/207 (99.5%) (95% CI, 98.6-100) in 2007-2008, 2012-2013, and 2014, respectively. There was no significant change in the trend of cure rate between 2007 and 2014 (χ2trend test = 0.06, P = 0.90). Pretreatment P. falciparum multidrug-resistant gene 1 (Pfmdr1) N86 prevalence increased significantly across years from 13/48 (27.1%) in 2006 to 183/213 (85.9%) in 2014 (P < 0.001), and P. falciparum chloroquine resistance transporter gene (Pfcrt) K76 prevalence increased significantly from 24/47 (51.1%) in 2006 to 198/205 (96.6%) in 2014 (P < 0.001). The AL cure rate remained high after 8 years of its wide-scale use in Bagamoyo district for the treatment of uncomplicated P. falciparum malaria despite an increase in prevalence of pretreatment Pfmdr1 N86 and Pfcrt K76 between 2006 and 2014.
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Affiliation(s)
- Richard Mwaiswelo
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Billy Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - J Pedro Gil
- Drug Resistance Unit, Division of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Maja Malmberg
- Section of Virology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Irina Jovel
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Weiping Xu
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Zul Premji
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Bruno P Mmbando
- National Institute for Medical Research, Tanga Centre, Tanga, Tanzania
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andreas Mårtensson
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden
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15
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Djouaka R, Akoton R, Tchigossou GM, Atoyebi SM, Irving H, Kusimo MO, Djegbe I, Riveron JM, Tossou E, Yessoufou A, Wondji CS. Mapping the distribution of Anopheles funestus across Benin highlights a sharp contrast of susceptibility to insecticides and infection rate to Plasmodium between southern and northern populations. Wellcome Open Res 2016. [PMID: 28191507 DOI: 10.12688/wellcomeopenres.10213.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Background. Malaria remains an important public health issue in Benin, with Anopheles gambiae s.l. and Anopheles funestus s.s being the predominant vectors. This study was designed to generate information on An. funestus distribution, molecular speciation, Plasmodium infection rate and insecticide susceptibility status across Benin. Methods. Mosquito samples were collected from December 2014 to January 2016 in 46 localities in Benin. These samples were mapped and An. funestus collected were speciated to the molecular level. Plasmodium infection rate was determined using a Taqman assay and susceptibility to insecticides was assessed using the WHO guidelines. The genotyping of the L119F- Gste2 mutation was also carried out. Results. An. funestus was found in 8 out of the 46 localities surveyed with a high presence in Tanongou (wet Sudanese ecological zone), Kpome, Doukonta and Pahou (sub-equatorial ecological zone). Molecular identifications revealed that only An. funestuss.s was present in southern Benin, whereas in Tanongou (northern Benin) An. funestus s.s. and An. leesoni were found in sympatry at proportions of 77.7% and 22.3% respectively. Plasmodium infection rate of An. funestus was higher in southern Benin at a range of 13 to 18% compared to 5.6% recorded in Tanongou. High DDT (8±0.5%) and permethrin (11±0.5%) resistance were observed in Doukonta, Kpome and Pahou, contrasting with relatively low resistance profiles: mortality-DDT=90±3.18% and mortality-permethrin=100% in Tanongou. Genotyping analysis revealed high frequency of the resistant 119F allele in the South (Kpome and Doukonta) compared to the North (Tanongou). Discussion and Conclusion. The high presence of An. funestus in the South compared to the North could be due to favorable environmental and climatic conditions found in both regions. A significant Plasmodium infection rate was recorded across the country. A high resistance profile was recorded in the southern Benin; this raises the need for further investigations on resistance selection factors.
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Affiliation(s)
| | - Romaric Akoton
- International Institute of Tropical Agriculture, Cotonou, Benin.,University of Abomey-Calavi, Cotonou, Benin
| | - Genevieve M Tchigossou
- International Institute of Tropical Agriculture, Cotonou, Benin.,University of Abomey-Calavi, Cotonou, Benin
| | - Seun M Atoyebi
- International Institute of Tropical Agriculture, Cotonou, Benin.,Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan, Nigeria
| | - Helen Irving
- Liverpool School of Tropical Medicine, Liverpool, UK
| | | | - Innocent Djegbe
- University of Sciences, Arts and Techniques of Natitingou, Ecole Normale Supérieure de Natitingou, Natitingou, Benin
| | | | - Eric Tossou
- International Institute of Tropical Agriculture, Cotonou, Benin.,University of Abomey-Calavi, Cotonou, Benin
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16
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Djouaka R, Akoton R, Tchigossou GM, Atoyebi SM, Irving H, Kusimo MO, Djegbe I, Riveron JM, Tossou E, Yessoufou A, Wondji CS. Mapping the distribution of Anopheles funestus across Benin highlights a sharp contrast of susceptibility to insecticides and infection rate to Plasmodium between southern and northern populations. Wellcome Open Res 2016; 1:28. [PMID: 28191507 PMCID: PMC5300096 DOI: 10.12688/wellcomeopenres.10213.2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2017] [Indexed: 11/20/2022] Open
Abstract
Background. Malaria remains an important public health issue in Benin, with Anopheles gambiae s.l. and Anopheles funestus s.s being the predominant vectors. This study was designed to generate information on An. funestus distribution, molecular speciation, Plasmodium infection rate and insecticide susceptibility status across Benin. Methods. Mosquito samples were collected from December 2014 to January 2016 in 46 localities in Benin. These samples were mapped and An. funestus collected were speciated to the molecular level. Plasmodium infection rate was determined using a Taqman assay and susceptibility to insecticides was assessed using the WHO guidelines. The genotyping of the L119F- Gste2 mutation was also carried out. Results. An. funestus was found in 8 out of the 46 localities surveyed with a high presence in Tanongou (wet Sudanese ecological zone), Kpome, Doukonta and Pahou (sub-equatorial ecological zone). Molecular identifications revealed that only An. funestuss.s was present in southern Benin, whereas in Tanongou (northern Benin) An. funestus s.s. and An. leesoni were found in sympatry at proportions of 77.7% and 22.3% respectively. Plasmodium infection rate of An. funestus was higher in southern Benin at a range of 13 to 18% compared to 5.6% recorded in Tanongou. High DDT (8±0.5%) and permethrin (11±0.5%) resistance were observed in Doukonta, Kpome and Pahou, contrasting with relatively low resistance profiles: mortality-DDT=90±3.18% and mortality-permethrin=100% in Tanongou. Genotyping analysis revealed high frequency of the resistant 119F allele in the South (Kpome and Doukonta) compared to the North (Tanongou). Discussion and Conclusion. The high presence of An. funestus in the South compared to the North could be due to favorable environmental and climatic conditions found in both regions. A significant Plasmodium infection rate was recorded across the country. A high resistance profile was recorded in the southern Benin; this raises the need for further investigations on resistance selection factors.
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Affiliation(s)
| | - Romaric Akoton
- International Institute of Tropical Agriculture, Cotonou, Benin
- University of Abomey-Calavi, Cotonou, Benin
| | - Genevieve M. Tchigossou
- International Institute of Tropical Agriculture, Cotonou, Benin
- University of Abomey-Calavi, Cotonou, Benin
| | - Seun M. Atoyebi
- International Institute of Tropical Agriculture, Cotonou, Benin
- Cell Biology and Genetics Unit, Department of Zoology, University of Ibadan, Ibadan, Nigeria
| | - Helen Irving
- Liverpool School of Tropical Medicine, Liverpool, UK
| | | | - Innocent Djegbe
- University of Sciences, Arts and Techniques of Natitingou, Ecole Normale Supérieure de Natitingou, Natitingou, Benin
| | | | - Eric Tossou
- International Institute of Tropical Agriculture, Cotonou, Benin
- University of Abomey-Calavi, Cotonou, Benin
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Mwaiswelo R, Ngasala B, Jovel I, Aydin-Schmidt B, Gosling R, Premji Z, Mmbando B, Björkman A, Mårtensson A. Adding a single low-dose of primaquine (0.25 mg/kg) to artemether-lumefantrine did not compromise treatment outcome of uncomplicated Plasmodium falciparum malaria in Tanzania: a randomized, single-blinded clinical trial. Malar J 2016; 15:435. [PMID: 27565897 PMCID: PMC5002101 DOI: 10.1186/s12936-016-1430-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 07/05/2016] [Indexed: 01/26/2023] Open
Abstract
Background The World Health Organization (WHO) recently recommended the addition of a single low-dose of the gametocytocidal drug primaquine (PQ) to artemisinin-based combination therapy (ACT) in low transmission settings as a component of pre-elimination or elimination programmes. However, it is unclear whether that influences the ACT cure rate. The study assessed treatment outcome of artemether-lumefantrine (AL) plus a single PQ dose (0.25 mg/kg) versus standard AL regimen for treatment of acute uncomplicated Plasmodium falciparum malaria in Tanzania. Methods A randomized, single-blinded, clinical trial was conducted in Yombo, Bagamoyo district, Tanzania. Acute uncomplicated P. falciparum malaria patients aged ≥1 year, with the exception of pregnant and lactating women, were enrolled and treated with AL plus a single PQ dose (0.25 mg/kg) or AL alone under supervision. PQ was administered together with the first AL dose. Clinical and laboratory assessments were performed at 0, 8, 24, 36, 48, 60, and 72 h and on days 7, 14, 21, and 28. The primary end-point was a polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR) on day 28. Secondary outcomes included: fever and asexual parasitaemia clearance, proportion of patients with PCR-determined parasitaemia on day 3, and proportion of patients with Pfmdr1 N86Y and Pfcrt K76T on days 0, 3 and day of recurrent infection. Results Overall 220 patients were enrolled, 110 were allocated AL + PQ and AL, respectively. Parasite clearance by microscopy was fast, but PCR detectable parasitaemia on day 3 was 31/109 (28.4 %) and 29/108 (26.9 %) in patients treated with AL + PQ and AL, respectively (p = 0.79). Day 28 PCR-adjusted ACPR and re-infection rate was 105/105 (100 %) and 101/102 (99 %) (p = 0.31), and 5/107 (4.7 %) and 5/8 (4.8 %) (p = 0.95), in AL + PQ and AL arm, respectively. There was neither any statistically significant difference in the proportion of Pfmdr1 N86Y or Pfcrt K76T between treatment arms on days 0, 3 and day of recurrent infection, nor within treatment arms between days 0 and 3 or day 0 and day of recurrent infection. Conclusion The new WHO recommendation of adding a single low-dose of PQ to AL did not compromise treatment outcome of uncomplicated P. falciparum malaria in Tanzania. Trial registration number NCT02090036 Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1430-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Richard Mwaiswelo
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar Es Salaam, Tanzania
| | - Billy Ngasala
- Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar Es Salaam, Tanzania.
| | - Irina Jovel
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Berit Aydin-Schmidt
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Roland Gosling
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA.,Global Health Group, University of California San Francisco, San Francisco, CA, USA
| | - Zul Premji
- Aga Khan University Hospital, Nairobi, Kenya
| | - Bruno Mmbando
- Tanga Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andreas Mårtensson
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden
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Al-Eryani SMA, Kelly-Hope L, Harbach RE, Briscoe AG, Barnish G, Azazy A, McCall PJ. Entomological aspects and the role of human behaviour in malaria transmission in a highland region of the Republic of Yemen. Malar J 2016; 15:130. [PMID: 26932794 PMCID: PMC4774125 DOI: 10.1186/s12936-016-1179-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 02/17/2016] [Indexed: 11/25/2022] Open
Abstract
Background The Republic of Yemen has the highest incidence of malaria in the Arabian Peninsula, yet little is known of its vectors or transmission dynamics. Methods A 24-month study of the vectors and related epidemiological aspects of malaria transmission was conducted in two villages in the Taiz region in 2004–2005. Results Cross-sectional blood film surveys recorded an overall malaria infection rate of 15.3 % (250/1638), with highest rates exceeding 30 % in one village in May and December 2005. With one exception, Plasmodium malariae, all infections were P.falciparum. Seven Anopheles species were identified among 3407 anophelines collected indoors using light traps (LT) and pyrethrum knockdown catches (PKD): Anopheles arabiensis (86.9 %), An. sergentii (9 %), An. azaniae, An. dthali, An. pretoriensis, An. coustani and An. algeriensis. Sequences for the standard barcode region of the mitochondrial COI gene confirmed the presence of two morphological forms of An. azaniae, the typical form and a previously unrecognized form not immediately identifiable as An. azaniae. ELISA detected Plasmodium sporozoites in 0.9 % of 2921 An. arabiensis (23 P. falciparum, two P. vivax) confirming this species as the primary malaria vector in Yemen. Plasmodium falciparum sporozoites were detected in An. sergentii (2/295) and a single female of An. algeriensis, incriminating both species as malaria vectors for the first time in Yemen. A vector in both wet and dry seasons, An. arabiensis was predominantly anthropophilic (human blood index = 0.86) with an entomological inoculation rate of 1.58 infective bites/person/year. Anopheles sergentii fed on cattle (67.3 %) and humans (48.3; 20.7 % mixed both species), but only 14.7 % were found in PKDs, indicating predominantly exophilic behaviour. A GIS analysis of geographic and socio-economic parameters revealed that An. arabiensis were significantly higher (P < 0.001) in houses with televisions, most likely due to the popular evening habit of viewing television collectively in houses with open doors and windows. Conclusions The predominantly indoor human biting vectors recorded in this study could be targeted effectively with LLINs, indoor residual spraying and/or insecticide-treated window/door curtains reinforced by education to instil a perception that effective and affordable malaria prevention is achievable. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1179-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Samira M A Al-Eryani
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK. .,Department of Medical Parasitology, Faculty of Medicine and Health Sciences, University of Yemen, Sana'a, Yemen.
| | - Louise Kelly-Hope
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Ralph E Harbach
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, UK.
| | - Andrew G Briscoe
- Department of Life Sciences, Natural History Museum, Cromwell Road, London, UK.
| | - Guy Barnish
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
| | - Ahmed Azazy
- Department of Medical Parasitology, Faculty of Medicine and Health Sciences, University of Yemen, Sana'a, Yemen.
| | - Philip J McCall
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK.
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Acheson ES, Plowright AA, Kerr JT. Where have all the mosquito nets gone? Spatial modelling reveals mosquito net distributions across Tanzania do not target optimal Anopheles mosquito habitats. Malar J 2015; 14:322. [PMID: 26283538 PMCID: PMC4539722 DOI: 10.1186/s12936-015-0841-x] [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: 05/05/2015] [Accepted: 08/06/2015] [Indexed: 11/10/2022] Open
Abstract
Background Malaria remains the deadliest vector-borne disease despite long-term, costly control efforts. The United Republic of Tanzania has implemented countrywide anti-malarial interventions over more than a decade, including national insecticide-treated net (ITN) rollouts and subsequent monitoring. While previous analyses have compared spatial variation in malaria endemicity with ITN distributions, no study has yet compared Anopheles habitat suitability to determine proper allocation of ITNs. This study assesses where mosquitoes were most likely to thrive before implementation of large-scale ITN interventions in Tanzania and determine if ITN distributions successfully targeted those areas. Methods Using Maxent, a species distribution model was constructed relating anopheline mosquito occurrences for 1999–2003 to high resolution environmental observations. A 2011–2012 layer of mosquito net ownership was created using georeferenced data across Tanzania from the Demographic and Health Surveys. The baseline mosquito habitat suitability was compared to subsequent ITN ownership using (1) the average ITN numbers per house and (2) the proportion of households with ≥1 net to test whether national ITN ownership targets have been met and have tracked malaria risk. Results Elevation, land cover, and human population distribution outperformed variants of temperature and Normalized Difference Vegetation Index (NDVI) in anopheline distribution models. The spatial distribution of ITN ownership across Tanzania was near-random spatially (Moran’s I = 0.07). Householders reported owning 2.488 ITNs on average and 93.41 % of households had ≥1 ITN. Mosquito habitat suitability was statistically unrelated to reported ITN ownership and very weakly to the proportion of households with ≥1 ITN (R2 = 0.051). Proportional ITN ownership/household varied relative to mosquito habitat suitability (Levene’s test F = 3.0037). Quantile regression was used to assess trends in ITN ownership among households with the highest and lowest 10 % of ITN ownership. ITN ownership declined significantly toward areas with the highest vector habitat suitability among households with lowest ITN ownership (t = −3.38). In areas with lowest habitat suitability, ITN ownership was consistently higher. Conclusions Insecticide-treated net ownership is critical for malaria control. While Tanzania-wide efforts to distribute ITNs has reduced malaria impacts, gaps and variance in ITN ownership are unexpectedly large in areas where malaria risk is highest. Supplemental ITN distributions targeting prime Anopheles habitats are likely to have disproportionate human health benefits. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0841-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Emily S Acheson
- Department of Biology, University of Ottawa, Gendron 352, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada.
| | - Andrew A Plowright
- Department of Biology, University of Ottawa, Gendron 352, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada.
| | - Jeremy T Kerr
- Department of Biology, University of Ottawa, Gendron 352, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada.
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Kipyab PC, Khaemba BM, Mwangangi JM, Mbogo CM. The physicochemical and environmental factors affecting the distribution of Anopheles merus along the Kenyan coast. Parasit Vectors 2015; 8:221. [PMID: 25889775 PMCID: PMC4396831 DOI: 10.1186/s13071-015-0819-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 03/20/2015] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Members of the Anopheles gambiae complex are the main transmitters of malaria. Anopheles merus is a member of the complex found along the Kenyan coast because it breeds in saline waters. An entomological study was conducted in Garithe Malindi District, to investigate the physicochemical and environmental factors affecting the distribution of An. merus. METHODS Field and laboratory studies were used to investigate the breeding habitats of the subspecies. Mosquito larvae were sampled using standard dipping technique from small pockets of pools, ponds, hoof prints, road drain, wells and mangrove swamps found in Garithe. All 3(rd) and 4(th) instars of Anopheles larvae sampled were identified microscopically into species. A representative of Anopheles gambiae complex was then identified to specific sibling species using r-DNA PCR technique. The habitats were characterized based on temperature, conductivity, salinity, dissolved oxygen, total dissolved solids, pH, size, distance to nearest house, canopy coverage, surface debris, presence of algae, emergent plants, turbidity and habitat types. RESULTS A total of 159 morphologically identified late stage instar Anopheles gambiae s.l larvae were selected for r-DNA analysis by PCR. Out of these, 60.4% (n = 96) were Anopheles merus, 8.8% (n = 14) were Anopheles arabiensis, 18.2% (n = 29) were Anopheles gambiae s.s and 12.6% (n = 20) were unknown. Using paired t-test (t (121) = -3.331, P = 0.001) a significantly high proportion of An. merus was observed in all habitats compared to An. arabiensis, and An. gambiae s. s. In habitat characterization, Pearson's correlation analysis test showed different parameters being associated with the occurrence of An. merus larvae in the different habitats sampled. Six out of the 55 correlation coefficients (10.9%) were statistically significant, suggesting non-random association between some pairs of variables. Those that had a significantly high positive correlation with An. merus included temperature, salinity, conductivity, total dissolved solids and algae. CONCLUSIONS Different physicochemical parameters and environmental parameters affect the occurrence of An. merus. In this study, higher temperatures accelerate the growth of the larvae and aids in growth of micro-organisms and algae which are food sources for the larvae. Saline waters favour the growth and development of An. merus larvae; they are also able to develop in a range of saline waters. Conductivity, total dissolved solids and canopy coverage are among the important factors influencing the development and abundance of An. merus larvae in their habitats. Habitat type also influences the abundance of An. merus larvae. They mainly prefer to breed in pools and ponds, but not swamps, hoof prints and wells.
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Affiliation(s)
- Pamela C Kipyab
- Kenya Medical Research Institute - Centre for Geographic Medicine Research-Coast, P.O Box 428, 80108, Kilifi, Kenya.
- Malaria Public Health Department, KEMRI-Wellcome Trust Research Programme, P.O. Box 43640, 00100, Nairobi, Kenya.
- Moi University, P.O Box 3900, 30100, Eldoret, Kenya.
| | | | - Joseph M Mwangangi
- Kenya Medical Research Institute - Centre for Geographic Medicine Research-Coast, P.O Box 428, 80108, Kilifi, Kenya.
- Malaria Public Health Department, KEMRI-Wellcome Trust Research Programme, P.O. Box 43640, 00100, Nairobi, Kenya.
| | - Charles M Mbogo
- Kenya Medical Research Institute - Centre for Geographic Medicine Research-Coast, P.O Box 428, 80108, Kilifi, Kenya.
- Malaria Public Health Department, KEMRI-Wellcome Trust Research Programme, P.O. Box 43640, 00100, Nairobi, Kenya.
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Sibling species of the Anopheles funestus group, and their infection with malaria and lymphatic filarial parasites, in archived and newly collected specimens from northeastern Tanzania. Malar J 2015; 14:104. [PMID: 25885457 PMCID: PMC4352238 DOI: 10.1186/s12936-015-0616-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Accepted: 02/20/2015] [Indexed: 11/13/2022] Open
Abstract
Background Studies on the East African coast have shown a recent dramatic decline in malaria vector density and change in composition of sibling species of the Anopheles gambiae complex, paralleled by a major decline in malaria incidence. In order to better understand the ongoing changes in vector-parasite dynamics in the area, and to allow for appropriate adjustment of control activities, the present study examined the composition, and malaria and lymphatic filarial infection, of sibling species of the Anopheles funestus group. Similar to the An. gambiae complex, the An. funestus group contains important vectors of both malaria and lymphatic filariasis. Methods Archived (from 2005–2012) and newly collected (from 2014) specimens of the An. funestus group collected indoors using CDC light traps in villages in northeastern Tanzania were analysed. They were identified to sibling species by PCR based on amplification of species-specific nucleotide sequence in the ITS2 region on rDNA genes. The specimens were furthermore examined for infection with Plasmodium falciparum and Wuchereria bancrofti by PCR. Results The identified sibling species were An. funestus s.s., Anopheles parensis, Anopheles rivulorum, and Anopheles leesoni, with the first being by far the most common (overall 94.4%). When comparing archived specimens from 2005–2007 to those from 2008–2012, a small but statistically significant decrease in proportion of An. funestus s.s. was noted, but otherwise observed temporal changes in sibling species composition were minor. No P. falciparum was detected in archived specimens, while 8.3% of the newly collected An. funestus s.s. were positive for this parasite. The overall W. bancrofti infection rate decreased from 14.8% in the 2005–2007 archived specimens to only 0.5% in the newly collected specimens, and with overall 93.3% of infections being in An. funestus s.s. Conclusion The study indicated that the composition of the An. funestus group had remained rather stable during the study period, with An. funestus s.s. being the most predominant. The study also showed increasing P. falciparum infection and decreasing W. bancrofti infection in An. funestus s.s. in the study period, most likely reflecting infection levels with these parasites in the human population in the area.
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Innocent E, Hassanali A, Kisinza WNW, Mutalemwa PPP, Magesa S, Kayombo E. Anti-mosquito plants as an alternative or incremental method for malaria vector control among rural communities of Bagamoyo District, Tanzania. JOURNAL OF ETHNOBIOLOGY AND ETHNOMEDICINE 2014; 10:56. [PMID: 25015092 PMCID: PMC4131773 DOI: 10.1186/1746-4269-10-56] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 07/01/2014] [Indexed: 05/02/2023]
Abstract
BACKGROUND Plants represent one of the most accessible resources available for mosquito control by communities in Tanzania. However, no documented statistics exist for their contribution in the management of mosquitoes and other insects except through verbal and some publications. This study aimed at assessing communities' knowledge, attitudes and practices of using plants as an alternative method for mosquito control among selected communities in a malaria-prone area in Tanzania. METHODS Questionnaires were administered to 202 respondents from four villages of Bagamoyo District, Pwani Region, in Tanzania followed by participatory rural appraisal with village health workers. Secondary data collection for plants mentioned by the communities was undertaken using different search engines such as googlescholar, PubMED and NAPRALERT. RESULTS Results showed about 40.3% of respondents used plants to manage insects, including mosquitoes. A broad profile of plants are used, including "mwarobaini" (Azadirachta indica) (22.5%), "mtopetope" (Annona spp) (20.8%), "mchungwa/mlimau" (Citrus spp) (8.3%), "mvumbashi/uvumbati" (Ocimum spp) (7.4%), "mkorosho" (Anacadium occidentale) (7.1%), "mwembe" (5.4%) (Mangifera indica), "mpera" (4.1%) (Psidium spp) and "maganda ya nazi" (4.1%) (Cocos nucifera). Majority of respondents collected these plants from the wild (54.2%), farms (28.9%) and/or home gardens (6%). The roles played by these plants in fighting mosquitoes is reflected by the majority that deploy them with or without bed-nets (p > 0.55) or insecticidal sprays (p >0.22). Most respondents were aware that mosquitoes transmit malaria (90.6%) while few respondents associated elephantiasis/hydrocele (46.5%) and yellow fever (24.3%) with mosquitoes. Most of the ethnobotanical uses mentioned by the communities were consistent with scientific information gathered from the literature, except for Psidium guajava, which is reported for the first time in insect control. CONCLUSION This survey has indicated some knowledge gap among community members in managing mosquito vectors using plant. The communities need a basic health education and sensitization for effective exploitation of this valuable tool for reducing mosquitoes and associated disease burdens. On the other hand, the government of Tanzania should strengthen advocacy of botanical pesticides development, registration and regulation for public health benefits because they are source of pest control tools people rely on them.
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Affiliation(s)
- Ester Innocent
- Institute of Traditional Medicine, Muhimbili University of Health and Allied Sciences, P.O. Box 65001, Dar es Salaam, Tanzania
| | - Ahmed Hassanali
- Department of Chemistry, School of Pure & Applied Sciences, Kenyatta University, P.O. Box 43844–00100, Nairobi, Kenya
| | - William NW Kisinza
- National Institute for Medical Research (NIMR), Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Prince PP Mutalemwa
- National Institute for Medical Research (NIMR), Amani Research Centre, P.O. Box 81, Muheza, Tanzania
| | - Stephen Magesa
- National Institute for Medical Research (NIMR), Amani Research Centre, P.O. Box 81, Muheza, Tanzania
- RTI International, Malaria Initiative, P.O. Box 1181–000621, Nairobi, Kenya
| | - Edmund Kayombo
- Institute of Traditional Medicine, Muhimbili University of Health and Allied Sciences, P.O. Box 65001, Dar es Salaam, Tanzania
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Mwangangi JM, Muturi EJ, Muriu SM, Nzovu J, Midega JT, Mbogo C. The role of Anopheles arabiensis and Anopheles coustani in indoor and outdoor malaria transmission in Taveta District, Kenya. Parasit Vectors 2013; 6:114. [PMID: 23601146 PMCID: PMC3652741 DOI: 10.1186/1756-3305-6-114] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 04/17/2013] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND The scaling up of malaria vector control efforts in Africa has resulted in changing the malaria vectorial systems across different ecological settings. In view of the ongoing trends in vector population dynamics, abundance, species composition and parasite infectiousness, there is a need to understand vector distribution and their contribution to malaria transmission to facilitate future planning of control strategies. We studied indoor and outdoor malaria transmission dynamics and vector population variability of Anopheles mosquitoes in Taveta district along the Kenyan Coast. METHODS Anopheles mosquitoes were collected indoors and outdoors in 4 ecologically different villages using CDC light traps (both indoor and outdoor) and aspiration method (day resting indoors; DRI) methods. Mosquitoes were examined for infection with P. falciparum sporozoites and blood feeding preferences using enzyme linked immunosorbent assay (ELISA). The An. gambiae and An. funestus complexes were identified by PCR technique to determine the sibling species composition. RESULTS A total of 4,004 Anopheles mosquitoes were collected consisting of 34.9%% (n = 1,397) An. gambiae s.1., 28.1% (n = 1,124) An. funestus s.l., 33.5% (n = 1,340) An. coustani and 3.6% (n = 143) An. pharoensis. A total of 14,654 culicine mosquitoes were collected, mainly Cx. quinquefasciatus. Of the total Anopheles collected, 3,729 were tested for P. falciparum sporozoite infection. The sporozoite transmission was found to be occurring both indoors and outdoors. The overall sporozoite infectivity was 0.68% (n = 2,486) indoors and 1.29% (n = 1,243) outdoors. Indoor and outdoor sporozoite infectivity and the vectorial systems varied across the 4 ecological villages. Entomological inoculation rates for the 4 villages indicate that there was site-to-site variation. In the 4 villages, Mwarusa had the highest EIRs with An. arabiensis, An. funestus and An. coustani contributing to 23.91, 11.96 and 23.91 infectious bites per person per year ib/p/year respectively. In Kiwalwa and Njoro outdoor EIR was significantly higher than indoors. CONCLUSIONS This study shows that malaria transmission is occurring both indoors and outdoors. The main vectors are An. arabiensis, An. funestus and An. coustani indoors while An. coustani is playing a major role in outdoor transmission. Effective malaria control programmes, should therefore include tools that target both indoor and outdoor transmission.
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Affiliation(s)
- Joseph M Mwangangi
- Kenya Medical Research Institute (KEMRI), Centre for Geographic Medicine Research Coast, P,O, Box 42880108, Kilifi, Kenya.
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Kipyab PC, Khaemba BM, Mwangangi JM, Mbogo CM. The bionomics of Anopheles merus (Diptera: Culicidae) along the Kenyan coast. Parasit Vectors 2013; 6:37. [PMID: 23410133 PMCID: PMC3584914 DOI: 10.1186/1756-3305-6-37] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Accepted: 02/01/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Anopheles merus, a sibling species of the Anopheles gambiae complex occurs along the East African coast but its biology and role in malaria transmission in this region is poorly understood. We evaluated the blood feeding pattern and the role of this species in malaria transmission in Malindi district, Coastal Kenya. METHODS Adult mosquitoes were collected indoors by CDC light traps and Pyrethrum Spray Catch and outdoors by CDC light traps. Anopheles females were identified to species by morphological characteristics and sibling species of An. gambiae complex distinguished by rDNA polymerase chain reaction (PCR). Screening for host blood meal sources and presence or absence of Plasmodium falciparum circumsporozoite proteins was achieved by Enzyme Linked Immunosorbent Assays (ELISA). RESULTS Anopheles merus comprised 77.8% of the 387 Anopheles gambiae s.l adults that were collected. Other sibling species of Anopheles gambiae s.l identified in the study site included An. arabiensis(3.6%), and An. gambiae s.s. (8%). The human blood index for An. merus was 0.12, while the sporozoite rate was 0.3%. CONCLUSION These findings suggest that An. merus can play a minor role in malaria transmission along the Kenyan Coast and should be a target for vector control which in turn could be applied in designing and implementing mosquito control programmes targeting marsh-breeding mosquitoes; with the ultimate goal being to reduce the transmission of malaria associated with these vectors.
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Affiliation(s)
- Pamela C Kipyab
- Kenya Medical Research Institute, Center for Geographic Medicine Research-Coast, Kilifi, Kenya.
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Battle KE, Gething PW, Elyazar IRF, Moyes CL, Sinka ME, Howes RE, Guerra CA, Price RN, Baird KJ, Hay SI. The global public health significance of Plasmodium vivax. ADVANCES IN PARASITOLOGY 2013. [PMID: 23199486 DOI: 10.1016/b978-0-12-397900-1.00001-3] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Plasmodium vivax occurs globally and thrives in both temperate and tropical climates. Here, we review the evidence of the biological limits of its contemporary distribution and the global population at risk (PAR) of the disease within endemic countries. We also review the most recent evidence for the endemic level of transmission within its range and discuss the implications for burden of disease assessments. Finally, the evidence-base for defining the contemporary distribution and PAR of P. vivax are discussed alongside a description of the vectors of human malaria within the limits of risk. This information along with recent data documenting the severe morbid and fatal consequences of P. vivax infection indicates that the public health significance of P. vivax is likely to have been seriously underestimated.
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Affiliation(s)
- Katherine E Battle
- Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
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Mahande AM, Dusfour I, Matias JR, Kweka EJ. Knockdown Resistance, rdl Alleles, and the Annual Entomological Inoculation Rate of Wild Mosquito Populations from Lower Moshi, Northern Tanzania. J Glob Infect Dis 2012; 4:114-9. [PMID: 22754247 PMCID: PMC3385201 DOI: 10.4103/0974-777x.96776] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Aim: Understanding vector behavioral response due to ecological factors is important in the control of disease vectors. This study was conducted to determine the knockdown resistance (kdr) alleles, dieldrin resistance alleles, and entomological inoculation rates (EIRs) of malaria vectors in lower Moshi irrigation schemes for the mitigation of disease transmission. Materials and Methods: The study was longitudinal design conducted for 14 months. Mosquitoes were collected fortnightly by using a CDC miniature light trap in 20 houses. Mosquitoes were identified morphologically in the field, of which 10% of this population was identified to species level by using molecular techniques. Samples from this study population were taken for kdr and resistance to dieldrin (rdl) genes detection. Results: A total of 6220 mosquitoes were collected by using a light trap, of which 86.0% (n=5350) were Anopheles gambiae sensu lato and 14.0% (n=870) were Culex quinquefasciatus. Ten percent of the An. gambiae s.l. (n=535) collected were taken for species identification, of which 99.8% (n=534) were identified as An. arabiensis while 0.2% (n=1) were An. gambiae sensu stricto. Of the selected mosquitoes, 3.5% (n=19) were sporozoite positive. None of the mosquitoes tested had the kdr gene. The rdl resistant allele was detected at a frequency of 0.48 throughout the year. EIR was determined to be 0.54 ib/trap/year. Conclusion: The findings of this study suggest that the homozygous and the heterozygous resistance present in rdl genes demonstrated the effect of pesticide residues on resistance selection pressure in mosquitoes. A better insecticide usage protocol needs to be developed for farmers to use in order to avoid excessive use of pesticides.
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Affiliation(s)
- Aneth M Mahande
- Tropical Pesticides Research Institute, Mabogini Field Station, Moshi, Tanzania
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Derua YA, Alifrangis M, Hosea KM, Meyrowitsch DW, Magesa SM, Pedersen EM, Simonsen PE. Change in composition of the Anopheles gambiae complex and its possible implications for the transmission of malaria and lymphatic filariasis in north-eastern Tanzania. Malar J 2012; 11:188. [PMID: 22681999 PMCID: PMC3469399 DOI: 10.1186/1475-2875-11-188] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 04/26/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A dramatic decline in the incidence of malaria due to Plasmodium falciparum infection in coastal East Africa has recently been reported to be paralleled (or even preceded) by an equally dramatic decline in malaria vector density, despite absence of organized vector control. As part of investigations into possible causes for the change in vector population density, the present study analysed the Anopheles gambiae s.l. sibling species composition in north-eastern Tanzania. METHODS The study was in two parts. The first compared current species complex composition in freshly caught An. gambiae s.l. complex from three villages to the composition reported from previous studies carried out 2-4 decades ago in the same villages. The second took advantage of a sample of archived dried An. gambiae s.l. complex specimens collected regularly from a fourth study village since 2005. Both fresh and archived dried specimens were identified to sibling species of the An. gambiae s.l. complex by PCR. The same specimens were moreover examined for Plasmodium falciparum and Wuchereria bancrofti infection by PCR. RESULTS As in earlier studies, An. gambiae s.s., Anopheles merus and Anopheles arabiensis were identified as sibling species found in the area. However, both study parts indicated a marked change in sibling species composition over time. From being by far the most abundant in the past An. gambiae s.s. was now the most rare, whereas An. arabiensis had changed from being the most rare to the most common. P. falciparum infection was rarely detected in the examined specimens (and only in An. arabiensis) whereas W. bancrofti infection was prevalent and detected in all three sibling species. CONCLUSION The study indicates that a major shift in An. gambiae s.l. sibling species composition has taken place in the study area in recent years. Combined with the earlier reported decline in overall malaria vector density, the study suggests that this decline has been most marked for An. gambiae s.s., and least for An. arabiensis, leading to current predominance of the latter. Due to differences in biology and vectorial capacity of the An. gambiae s.l. complex the change in sibling species composition will have important implications for the epidemiology and control of malaria and lymphatic filariasis in the study area.
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Affiliation(s)
- Yahya A Derua
- National Institute for Medical Research, Amani Centre, P, O, Box 81, Muheza, Tanzania.
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Sinka ME, Bangs MJ, Manguin S, Coetzee M, Mbogo CM, Hemingway J, Patil AP, Temperley WH, Gething PW, Kabaria CW, Okara RM, Van Boeckel T, Godfray HCJ, Harbach RE, Hay SI. The dominant Anopheles vectors of human malaria in Africa, Europe and the Middle East: occurrence data, distribution maps and bionomic précis. Parasit Vectors 2010; 3:117. [PMID: 21129198 PMCID: PMC3016360 DOI: 10.1186/1756-3305-3-117] [Citation(s) in RCA: 411] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 12/03/2010] [Indexed: 11/10/2022] Open
Abstract
Background This is the second in a series of three articles documenting the geographical distribution of 41 dominant vector species (DVS) of human malaria. The first paper addressed the DVS of the Americas and the third will consider those of the Asian Pacific Region. Here, the DVS of Africa, Europe and the Middle East are discussed. The continent of Africa experiences the bulk of the global malaria burden due in part to the presence of the An. gambiae complex. Anopheles gambiae is one of four DVS within the An. gambiae complex, the others being An. arabiensis and the coastal An. merus and An. melas. There are a further three, highly anthropophilic DVS in Africa, An. funestus, An. moucheti and An. nili. Conversely, across Europe and the Middle East, malaria transmission is low and frequently absent, despite the presence of six DVS. To help control malaria in Africa and the Middle East, or to identify the risk of its re-emergence in Europe, the contemporary distribution and bionomics of the relevant DVS are needed. Results A contemporary database of occurrence data, compiled from the formal literature and other relevant resources, resulted in the collation of information for seven DVS from 44 countries in Africa containing 4234 geo-referenced, independent sites. In Europe and the Middle East, six DVS were identified from 2784 geo-referenced sites across 49 countries. These occurrence data were combined with expert opinion ranges and a suite of environmental and climatic variables of relevance to anopheline ecology to produce predictive distribution maps using the Boosted Regression Tree (BRT) method. Conclusions The predicted geographic extent for the following DVS (or species/suspected species complex*) is provided for Africa: Anopheles (Cellia) arabiensis, An. (Cel.) funestus*, An. (Cel.) gambiae, An. (Cel.) melas, An. (Cel.) merus, An. (Cel.) moucheti and An. (Cel.) nili*, and in the European and Middle Eastern Region: An. (Anopheles) atroparvus, An. (Ano.) labranchiae, An. (Ano.) messeae, An. (Ano.) sacharovi, An. (Cel.) sergentii and An. (Cel.) superpictus*. These maps are presented alongside a bionomics summary for each species relevant to its control.
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Affiliation(s)
- Marianne E Sinka
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.
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Kulkarni MA, Desrochers RE, Kerr JT. High resolution niche models of malaria vectors in northern Tanzania: a new capacity to predict malaria risk? PLoS One 2010; 5:e9396. [PMID: 20195366 PMCID: PMC2827547 DOI: 10.1371/journal.pone.0009396] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 02/05/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Malaria transmission rates in Africa can vary dramatically over the space of a few kilometres. This spatial heterogeneity reflects variation in vector mosquito habitat and presents an important obstacle to the efficient allocation of malaria control resources. Malaria control is further complicated by combinations of vector species that respond differently to control interventions. Recent modelling innovations make it possible to predict vector distributions and extrapolate malaria risk continentally, but these risk mapping efforts have not yet bridged the spatial gap to guide on-the-ground control efforts. METHODOLOGY/PRINCIPAL FINDINGS We used Maximum Entropy with purpose-built, high resolution land cover data and other environmental factors to model the spatial distributions of the three dominant malaria vector species in a 94,000 km(2) region of east Africa. Remotely sensed land cover was necessary in each vector's niche model. Seasonality of precipitation and maximum annual temperature also contributed to niche models for Anopheles arabiensis and An. funestus s.l. (AUC 0.989 and 0.991, respectively), but cold season precipitation and elevation were important for An. gambiae s.s. (AUC 0.997). Although these niche models appear highly accurate, the critical test is whether they improve predictions of malaria prevalence in human populations. Vector habitat within 1.5 km of community-based malaria prevalence measurements interacts with elevation to substantially improve predictions of Plasmodium falciparum prevalence in children. The inclusion of the mechanistic link between malaria prevalence and vector habitat greatly improves the precision and accuracy of prevalence predictions (r(2) = 0.83 including vector habitat, or r(2) = 0.50 without vector habitat). Predictions including vector habitat are unbiased (observations vs. model predictions of prevalence: slope = 1.02). Using this model, we generate a high resolution map of predicted malaria prevalence throughout the study region. CONCLUSIONS/SIGNIFICANCE The interaction between mosquito niche space and microclimate along elevational gradients indicates worrisome potential for climate and land use changes to exacerbate malaria resurgence in the east African highlands. Nevertheless, it is possible to direct interventions precisely to ameliorate potential impacts.
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Affiliation(s)
- Manisha A Kulkarni
- Canadian Facility for Ecoinformatics Research, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
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Kawada H, Temu EA, Minjas JN, Matsumoto O, Iwasaki T, Takagi M. Field evaluation of spatial repellency of metofluthrin-impregnated plastic strips against Anopheles gambiae complex in Bagamoyo, coastal Tanzania. JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION 2008; 24:404-409. [PMID: 18939693 DOI: 10.2987/5743.1] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Metofluthrin is a newly synthesized pyrethroid possessing high knockdown and lethal activity against mosquitoes. Studies of metofluthrin-impregnated plastic strips have been performed with dengue vectors. This study reports the efficacy of the new prototypes of metofluthrin-impregnated plastic strips against malaria vectors, Anopheles gambiae complex, in the Kongo villages of Bagamoyo district in coastal Tanzania. The study, using 20 houses, half intervention, half control, was conducted for a 124-day period. Pyrethrum spray sheets and Centers for Disease Control and Prevention light traps were used to sample mosquito population indices. The mosquito density indices of the intervention houses were observed to be significantly lower than those of the control houses when pyrethrum spray sheet collection was used (F = 4.61, 1 df, P = 0.038; 98.7% reduction of total mosquito collection compared with that for the controls). These low indices were observed despite the large openings found in Bagamoyo houses, which were predicted to have a considerable negative effect on the spatial repellency of metofluthrin. Based on the present results, the pyrethrum spray sheet collection was the better of the 2 collection methods.
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Affiliation(s)
- Hitoshi Kawada
- Department of Vector Ecology & Environment, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan
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Kweka EJ, Nkya WMM, Mahande AM, Assenga C, Mosha FW, Lyatuu EE, Massenga CP, Nyale EM, Mwakalinga SB, Lowassa A. Mosquito abundance, bed net coverage and other factors associated with variations in sporozoite infectivity rates in four villages of rural Tanzania. Malar J 2008; 7:59. [PMID: 18423018 PMCID: PMC2358915 DOI: 10.1186/1475-2875-7-59] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Accepted: 04/18/2008] [Indexed: 11/22/2022] Open
Abstract
Background Entomological surveys are of great importance in decision-making processes regarding malaria control strategies because they help to identify associations between vector abundance both species-specific ecology and disease intervention factors associated with malaria transmission. Sporozoite infectivity rates, mosquito host blood meal source, bed net coverage and mosquito abundance were assessed in this study. Methodology A longitudinal survey was conducted in four villages in two regions of Tanzania. Malaria vectors were sampled using the CDC light trap and pyrethrum spray catch methods. In each village, ten paired houses were selected for mosquitoes sampling. Sampling was done in fortnight case and study was undertaken for six months in both Kilimanjaro (Northern Tanzania) and Dodoma (Central Tanzania) regions. Results A total of 6,883 mosquitoes were collected including: 5,628 (81.8%) Anopheles arabiensis, 1,100 (15.9%) Culex quinquefasciatus, 89 (1.4%) Anopheles funestus, and 66 (0.9%) Anopheles gambiae s.s. Of the total mosquitoes collected 3,861 were captured by CDC light trap and 3,022 by the pyrethrum spray catch method. The overall light trap: spray catch ratio was 1.3:1. Mosquito densities per room were 96.5 and 75.5 for light trap and pyrethrum spray catch respectively. Mosquito infectivity rates between villages that have high proportion of bed net owners and those without bed nets was significant (P < 0.001) and there was a significant difference in sporozoite rates between households with and without bed nets in these four villages (P < 0.001). Conclusion Malaria remains a major problem in the study areas characterized as low transmission sites. Further studies are required to establish the annual entomological inoculation rates and to observe the annual parasitaemia dynamics in these communities. Outdoor mosquitoes collection should also be considered.
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Affiliation(s)
- Eliningaya J Kweka
- Tropical Pesticides Research Institute, Division of Livestock and Human Disease Vector Control, P.O. Box 3024, Arusha, Tanzania.
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Temu EA, Minjas JN, Tuno N, Kawada H, Takagi M. Identification of four members of the Anopheles funestus (Diptera: Culicidae) group and their role in Plasmodium falciparum transmission in Bagamoyo coastal Tanzania. Acta Trop 2007; 102:119-25. [PMID: 17537390 DOI: 10.1016/j.actatropica.2007.04.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 02/21/2007] [Accepted: 04/17/2007] [Indexed: 10/23/2022]
Abstract
The role of Anopheles funestus group in malaria transmission was investigated in Bagamoyo coastal Tanzania, in the process of characterizing the area as a malaria vaccine testing site. Mosquitoes were sampled inside houses and multiplex PCR was used to identify 649 specimens. The following species were found: A. funestus s.s. (84.3%), A. leesoni (13.6%), A. rivulorum (1.5%) and A. parensis (0.6%). Multiplex PCR of 147 blood-fed specimens showed that over half (57.1%) of the identifiable blood meals were taken from human hosts, and human blood index in A. funestus and A. leesoni was 55% and 82% respectively. Plasmodium falciparum infection rate determined by nested PCR was 11% in A. funestus s.s. Although the abundance was low, 26 specimens of A. leesoni, two of A. rivolurum and one of A. parensis were found positive for P. falciparum. The presence of four A. funestus species in Tanzania emphasizes the relevance to define precisely their spatial and temporal distribution, specific behaviour, ecology and exact role in malaria transmission.
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Affiliation(s)
- E A Temu
- Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
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Malaria vectors and transmission dynamics in coastal south-western Cameroon. Malar J 2007; 6:5. [PMID: 17233883 PMCID: PMC1783660 DOI: 10.1186/1475-2875-6-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2006] [Accepted: 01/17/2007] [Indexed: 11/18/2022] Open
Abstract
Background Malaria is a major public health problem in Cameroon. Unlike in the southern forested areas where the epidemiology of malaria has been better studied prior to the implementation of control activities, little is known about the distribution and role of anophelines in malaria transmission in the coastal areas. Methods A 12-month longitudinal entomological survey was conducted in Tiko, Limbe and Idenau from August 2001 to July 2002. Mosquitoes captured indoors on human volunteers were identified morphologically. Species of the Anopheles gambiae complex were identified using the polymerase chain reaction (PCR). Mosquito infectivity was detected by the enzyme-linked immunosorbent assay and PCR. Malariometric indices (plasmodic index, gametocytic index, parasite species prevalence) were determined in three age groups (<5 yrs, 5–15 yrs, >15 yrs) and followed-up once every three months. Results In all, 2,773 malaria vectors comprising Anopheles gambiae (78.2%), Anopheles funestus (17.4%) and Anopheles nili (7.4%) were captured. Anopheles melas was not anthropophagic. Anopheles gambiae had the highest infection rates. There were 287, 160 and 149 infective bites/person/year in Tiko, Limbe and Idenau, respectively. Anopheles gambiae accounted for 72.7%, An. funestus for 23% and An. nili for 4.3% of the transmission. The prevalence of malaria parasitaemia was 41.5% in children <5 years of age, 31.5% in those 5–15 years and 10.5% in those >15 years, and Plasmodium falciparum was the predominant parasite species. Conclusion Malaria transmission is perennial, rainfall dependent and An. melas does not contribute to transmission. These findings are important in the planning and implementation of malaria control activities in coastal Cameroon and West Africa.
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Koekemoer LL, Kamau L, Garros C, Manguin S, Hunt RH, Coetzee M. Impact of the Rift Valley on restriction fragment length polymorphism typing of the major African malaria vector Anopheles funestus (Diptera: Culicidae). JOURNAL OF MEDICAL ENTOMOLOGY 2006; 43:1178-84. [PMID: 17162950 DOI: 10.1603/0022-2585(2006)43[1178:iotrvo]2.0.co;2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Anopheles funestus Giles (Diptera: Culicidae) is one of Africa's major malaria vectors. To understand population structure within An. funestus, various molecular markers have recently been developed. We investigated the impact of the Rift Valley on one such molecular marker, a polymerase chain reaction-restriction fragment length polymorphism (RFLP). This system distinguishes An. funestus populations into types M, W, and MW. Generally, these types correlate between geographical location and RFLP type, whereby M associates essentially with eastern Africa, W with western and central Africa, and MW with southern Africa. In total, 606 specimens were screened from 12 countries. Specimens from southern African localities were of the expected MW-type with the exception of the sample from Malawi, which showed all three types. The specimens from Tanzania showed the M- and MW-types, whereas specimens from Kenya showed M- and W-types. We also recorded different RFLP types not recorded previously. Type Y was recorded in Malawi, and Z-type was recorded from four localities: Angola, Malawi, Ghana, and Zambia.
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Affiliation(s)
- Lizette L Koekemoer
- Vector Control Reference Unit, National Institute for Communicable Diseases, Private bag X 4, Sandringham, 2131, South Africa.
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Marrama L, Jambou R, Rakotoarivony I, Leong Pock Tsi JM, Duchemin JB, Laventure S, Mouchet J, Roux J. Malaria transmission in Southern Madagascar: influence of the environment and hydro-agricultural works in sub-arid and humid regions. Part 1. Entomological investigations. Acta Trop 2004; 89:193-203. [PMID: 14732241 DOI: 10.1016/j.actatropica.2003.09.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A 4-year entomological study was carried out in Southern Madagascar to identify malaria vectors, evaluate the transmission and compare the influence of irrigation in the sub-arid and adjacent humid regions. Three villages were involved in this entomological survey: Androvasoa (located in the natural sub-arid ecosystem), Pépiniére (sited at the centre of an irrigated rice scheme in the sub-arid region) and Esana (bordered with rice fields in the humid region). Mosquitoes were collected inside and outside dwellings when landing on human beings, with light traps and with knockdown indoor sprays. Anopheles arabiensis, Anopheles merus and Anopheles funestus were found in every village while Anopheles gambiae s.s. was only found in the village bordering the rice-fields (Pépiniére) and Anopheles mascarensis, a mosquito native to Madagascar, was only found in the humid region (Esana). In Pépiniére, the annual entomological inoculation rate (EIR) was low (EIR=0.4 infective bites/man/year (IBM)). In the irrigated scheme of the sub-arid region, malaria transmission was 150 times higher (mean EIR=63 IBM) than in the natural ecosystem and A. funestus was the main vector, responsible for 90% of infective bites. In Esana, the level of malaria transmission was high (EIR=41 IBM) and 2/3 of the infective bites were due to A. mascarensis, despite the presence of A. gambiae s.s. and A. funestus. These results are discussed with reference to the impact of irrigation on malaria in Africa ("the paddies paradox").
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Affiliation(s)
- L Marrama
- Unité d' Epidémiologie de l'Institut Pasteur de Dakar, 36 Avenue Pasteur, BP 220, Dakar, Senegal.
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Pock Tsy JML, Duchemin JB, Marrama L, Rabarison P, Le Goff G, Rajaonarivelo V, Robert V. Distribution of the species of the Anopheles gambiae complex and first evidence of Anopheles merus as a malaria vector in Madagascar. Malar J 2003; 2:33. [PMID: 14609436 PMCID: PMC269986 DOI: 10.1186/1475-2875-2-33] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Accepted: 10/08/2003] [Indexed: 11/30/2022] Open
Abstract
Background Members of the Anopheles gambiae complex are amongst the best malaria vectors in the world, but their vectorial capacities vary between species and populations. A large-scale sampling of An. gambiae sensu lato was carried out in various bioclimatic domains of Madagascar. Local abundance of an unexpected member of this complex raised questions regarding its role in malaria transmission. Methods Sampling took place at 38 sites and 2,067 females were collected. Species assessment was performed using a PCR targeting a sequence in the IGS of the rDNA. Analysis focused on the relative prevalence of the species per site, bioclimatic domain and altitude. Infectivity of Anopheles merus was assessed using an ELISA to detect the presence of malarial circumsporozoite protein in the head-thorax. Results Three species were identified: An. gambiae, Anopheles arabiensis and An. merus. The distribution of each species is mainly a function of bioclimatic domains and, to a lesser extent, altitude. An. arabiensis is present in all bioclimatic domains with highest prevalence in sub-humid, dry and sub-arid domains. An. gambiae has its highest prevalence in the humid domain, is in the minority in dry areas, rare in sub-humid and absent in sub-arid domains. An. merus is restricted to the coastal fringe in the south and west; it was in the majority in one southern village. The majority of sites were sympatric for at least two of the species (21/38) and two sites harboured all three species. The role of An. merus as malaria vector was confirmed in the case of two human-biting females, which were ELISA-positive for Plasmodium falciparum. Conclusion Despite the huge environmental (mainly man-made) changes in Madagascar, the distribution of An. gambiae and An. arabiensis appears unchanged for the past 35 years. The distribution of An. merus is wider than was previously known, and its effectiveness as a malaria vector has been shown for the first time; this species is now on the list of Malagasy malaria vectors.
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Affiliation(s)
- Jean-Michel Léong Pock Tsy
- Groupe de Recherche sur le Paludisme, Laboratoire d'Entomologie Médicale, Institut Pasteur de Madagascar, B.P. 1274, Antananarivo 101, Madagascar
| | - Jean-Bernard Duchemin
- Groupe de Recherche sur le Paludisme, Laboratoire d'Entomologie Médicale, Institut Pasteur de Madagascar, B.P. 1274, Antananarivo 101, Madagascar
- CERMES, B.P. 10887, Niamey, Niger
| | - Laurence Marrama
- Unité d'Epidémiologie, Institut Pasteur de Dakar, B.P. 220 Dakar, Sénégal
| | - Patrick Rabarison
- Unité d'Entomologie Médicale, Institut Pasteur de Guyane, B.P. 6010, 97306 Cayenne, France
| | - Gilbert Le Goff
- Groupe de Recherche sur le Paludisme, Laboratoire d'Entomologie Médicale, Institut Pasteur de Madagascar, B.P. 1274, Antananarivo 101, Madagascar
- Institut de Recherche pour le Développement, B.P. 434, Antananarivo 101, Madagascar
| | - Voahirana Rajaonarivelo
- Groupe de Recherche sur le Paludisme, Laboratoire d'Entomologie Médicale, Institut Pasteur de Madagascar, B.P. 1274, Antananarivo 101, Madagascar
- Institut de Recherche pour le Développement, B.P. 434, Antananarivo 101, Madagascar
| | - Vincent Robert
- Groupe de Recherche sur le Paludisme, Laboratoire d'Entomologie Médicale, Institut Pasteur de Madagascar, B.P. 1274, Antananarivo 101, Madagascar
- Institut de Recherche pour le Développement, B.P. 434, Antananarivo 101, Madagascar
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Sylla EH, Kun JF, Kremsner PG. Mosquito distribution and entomological inoculation rates in three malaria-endemic areas in Gabon. Trans R Soc Trop Med Hyg 2000; 94:652-6. [PMID: 11198649 DOI: 10.1016/s0035-9203(00)90219-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Mosquitoes were collected during 3 separate periods in 3 areas of different malaria transmission rates in the province of Moyen Ogooué, Gabon, within 1 year (July 1996-May 1997). The campus of the Albert Schweitzer Hospital (HAS) and 2 villages, Bellevue and Tchad, were investigated. A total of 19,836 specimens were collected: 13,122 Mansonia, 3944 Anopheles, 2755 Culex and 15 Aedes were captured. The number of mosquitoes was 7896 and 7995 in July to August and from April to May respectively, and dropped to approximately half in November to December. The individual species showed a different distribution pattern in the 3 study areas. In Tchad we found the lowest number of mosquitoes and also the fewest Anopheles, but when we investigated the number of Plasmodium falciparum-infected Anopheles sp. we observed the highest entomological inoculation rate (EIR) there. The EIRs were 23 in HAS, 53 in Bellevue and 61 in Tchad. The method used to determine the number of infected mosquitoes was an enzyme-linked immunosorbent assay (ELISA), confirmed by a polymerase chain reaction-based approach. The ELISA alone revealed too many false-positive mosquitoes.
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Affiliation(s)
- E H Sylla
- Department of Parasitology, Institute of Tropical Medicine, University of Tübingen, Wilhelmstrasse 27, D-72074 Tübingen, Germany
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Hay SI, Rogers DJ, Toomer JF, Snow RW. Annual Plasmodium falciparum entomological inoculation rates (EIR) across Africa: literature survey, Internet access and review. Trans R Soc Trop Med Hyg 2000; 94:113-27. [PMID: 10897348 PMCID: PMC3204456 DOI: 10.1016/s0035-9203(00)90246-3] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
This paper presents the results of an extensive search of the formal and informal literature on annual Plasmodium falciparum entomological inoculation rates (EIR) across Africa from 1980 onwards. It first describes how the annual EIR data were collated, summarized, geo-referenced and staged for public access on the internet. Problems of data standardization, reporting accuracy and the subsequent publishing of information on the internet follow. The review was conducted primarily to investigate the spatial heterogeneity of malaria exposure in Africa and supports the idea of highly heterogeneous risk at the continental, regional and country levels. The implications for malaria control of the significant spatial (and seasonal) variation in exposure to infected mosquito bites are discussed.
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Affiliation(s)
- S I Hay
- Department of Zoology, University of Oxford, UK.
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Takken W, Eling W, Hooghof J, Dekker T, Hunt R, Coetzee M. Susceptibility of Anopheles quadriannulatus Theobald (Diptera: Culicidae) to Plasmodium falciparum. Trans R Soc Trop Med Hyg 1999; 93:578-80. [PMID: 10717736 DOI: 10.1016/s0035-9203(99)90054-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Anopheles quadriannulatus, the cattle-feeding member of the An. gambiae complex, was fed human blood which contained cultured gametocytes of Plasmodium falciparum, using a membrane feeding system. After 7 days, 33-80% of the mosquitoes that took a blood meal contained developing oocysts. In 7 out of 12 females sporozoites were found in the salivary glands 14 days after the infectious blood meal. Control groups of An. gambiae s.s. and An. stephensi became readily infected with > 90% developing oocysts. All of the An. gambiae dissected 14 days after the infectious blood meal had sporozoites in their salivary glands. The results demonstrate that An. quadriannulatus is susceptible to infections with P. falciparum.
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Affiliation(s)
- W Takken
- Laboratory of Entomology, Wageningen Agricultural University, The Netherlands.
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Koekemoer LL, Lochouarn L, Hunt RH, Coetzee M. Single-strand conformation polymorphism analysis for identification of four members of the Anopheles funestus (Diptera: Culicidae) group. JOURNAL OF MEDICAL ENTOMOLOGY 1999; 36:125-130. [PMID: 10083746 DOI: 10.1093/jmedent/36.2.125] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Members of the Anopheles funestus Giles group are difficult to identify because of the morphological overlap that exists within the group. This inability to distinguish species, as well as the fact that the species vary in their behavior and biting preferences, complicate the successful planning and maintaining of malaria control programs. In this article we discuss the use of a single-strand conformation polymorphism (SSCP) assay to distinguish 4 members of the An. funestus group collected at 10 different localities in Africa. rDNA genes differ at numerous sites among closely related species. Using conserved primers, the D3 domain in the 28S gene was amplified, electrophoresed on SSCP gels, and species-specific patterns were observed. Intraspecific variation was detected in An. funestus specimens from East and West Africa. Analyzing 108 An. funestus, 78 An. vaneedeni Gillies & Coetzee, 21 An. rivulorum Leeson, and 2 An. lessoni Evans, we concluded that SSCPs can be used successfully as a molecular tool for the identification of these species.
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Affiliation(s)
- L L Koekemoer
- Department of Tropical Diseases, School of Pathology, South African Institute for Medical Research, Johannesburg, South Africa
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