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Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control

BACKGROUND: Despite large reductions in malaria burden across Zambia, some regions continue to experience extremely high malaria transmission. In Nchelenge District, Luapula Province, northern Zambia, almost half the human population carries parasites. Intervention coverage has increased substantial...

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Autores principales: Stevenson, Jennifer C., Pinchoff, Jessie, Muleba, Mbanga, Lupiya, James, Chilusu, Hunter, Mwelwa, Ian, Mbewe, David, Simubali, Limonty, Jones, Christine M., Chaponda, Mike, Coetzee, Maureen, Mulenga, Modest, Pringle, Julia C., Shields, Tim, Curriero, Frank C., Norris, Douglas E.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5031275/
https://www.ncbi.nlm.nih.gov/pubmed/27655231
http://dx.doi.org/10.1186/s13071-016-1786-9
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author Stevenson, Jennifer C.
Pinchoff, Jessie
Muleba, Mbanga
Lupiya, James
Chilusu, Hunter
Mwelwa, Ian
Mbewe, David
Simubali, Limonty
Jones, Christine M.
Chaponda, Mike
Coetzee, Maureen
Mulenga, Modest
Pringle, Julia C.
Shields, Tim
Curriero, Frank C.
Norris, Douglas E.
author_facet Stevenson, Jennifer C.
Pinchoff, Jessie
Muleba, Mbanga
Lupiya, James
Chilusu, Hunter
Mwelwa, Ian
Mbewe, David
Simubali, Limonty
Jones, Christine M.
Chaponda, Mike
Coetzee, Maureen
Mulenga, Modest
Pringle, Julia C.
Shields, Tim
Curriero, Frank C.
Norris, Douglas E.
author_sort Stevenson, Jennifer C.
collection PubMed
description BACKGROUND: Despite large reductions in malaria burden across Zambia, some regions continue to experience extremely high malaria transmission. In Nchelenge District, Luapula Province, northern Zambia, almost half the human population carries parasites. Intervention coverage has increased substantially over the past decade, but comprehensive district-wide entomological studies to guide delivery of vector control measures are lacking. This study describes the bionomics and spatio-temporal patterns of malaria vectors in Nchelenge over a two and a half year period, investigates what household factors are associated with high vector densities and determines why vector control may not have been effective in the past to better guide future control efforts. METHODS: Between April 2012 and September 2014, twenty-seven households from across Nchelenge District were randomly selected for monthly light trap collections of mosquitoes. Anopheline mosquitoes were identified morphologically and molecularly to species. Foraging rates were estimated and sporozoite rates were determined by circumsporozoite ELISAs to calculate annual entomological inoculation rates. Blood feeding rates and host preference were determined by PCR. Zero-inflated negative binomial models measured environmental and household factors associated with mosquito abundance at study households such as season, proximity to the lake, and use of vector control measures. RESULTS: The dominant species in Nchelenge was An. funestus (s.s.) with An. gambiae (s.s.) as a secondary vector. Both vectors were found together in large numbers across the district and the combined EIRs of the two vectors exceeded 80 infectious bites per person per annum. An. funestus household densities increased in the dry season whilst An. gambiae surged during the rains. Presence of insecticide treated nets (ITNs) and closed eaves in the houses were found to be associated with fewer numbers of An. gambiae but not An. funestus. There was no association with indoor residual spraying (IRS). CONCLUSION: In Nchelenge, the co-existence of two highly anthropophagic vectors, present throughout the year, is likely to be driving the high malaria transmission evident in the district. The vectors here have been shown to be highly resistant to pyrethroids used for IRS during the study. Vector control interventions in this area would have to be multifaceted and district-wide for effective control of malaria. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1786-9) contains supplementary material, which is available to authorized users.
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spelling pubmed-50312752016-09-29 Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control Stevenson, Jennifer C. Pinchoff, Jessie Muleba, Mbanga Lupiya, James Chilusu, Hunter Mwelwa, Ian Mbewe, David Simubali, Limonty Jones, Christine M. Chaponda, Mike Coetzee, Maureen Mulenga, Modest Pringle, Julia C. Shields, Tim Curriero, Frank C. Norris, Douglas E. Parasit Vectors Research BACKGROUND: Despite large reductions in malaria burden across Zambia, some regions continue to experience extremely high malaria transmission. In Nchelenge District, Luapula Province, northern Zambia, almost half the human population carries parasites. Intervention coverage has increased substantially over the past decade, but comprehensive district-wide entomological studies to guide delivery of vector control measures are lacking. This study describes the bionomics and spatio-temporal patterns of malaria vectors in Nchelenge over a two and a half year period, investigates what household factors are associated with high vector densities and determines why vector control may not have been effective in the past to better guide future control efforts. METHODS: Between April 2012 and September 2014, twenty-seven households from across Nchelenge District were randomly selected for monthly light trap collections of mosquitoes. Anopheline mosquitoes were identified morphologically and molecularly to species. Foraging rates were estimated and sporozoite rates were determined by circumsporozoite ELISAs to calculate annual entomological inoculation rates. Blood feeding rates and host preference were determined by PCR. Zero-inflated negative binomial models measured environmental and household factors associated with mosquito abundance at study households such as season, proximity to the lake, and use of vector control measures. RESULTS: The dominant species in Nchelenge was An. funestus (s.s.) with An. gambiae (s.s.) as a secondary vector. Both vectors were found together in large numbers across the district and the combined EIRs of the two vectors exceeded 80 infectious bites per person per annum. An. funestus household densities increased in the dry season whilst An. gambiae surged during the rains. Presence of insecticide treated nets (ITNs) and closed eaves in the houses were found to be associated with fewer numbers of An. gambiae but not An. funestus. There was no association with indoor residual spraying (IRS). CONCLUSION: In Nchelenge, the co-existence of two highly anthropophagic vectors, present throughout the year, is likely to be driving the high malaria transmission evident in the district. The vectors here have been shown to be highly resistant to pyrethroids used for IRS during the study. Vector control interventions in this area would have to be multifaceted and district-wide for effective control of malaria. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1786-9) contains supplementary material, which is available to authorized users. BioMed Central 2016-09-21 /pmc/articles/PMC5031275/ /pubmed/27655231 http://dx.doi.org/10.1186/s13071-016-1786-9 Text en © The Author(s). 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Stevenson, Jennifer C.
Pinchoff, Jessie
Muleba, Mbanga
Lupiya, James
Chilusu, Hunter
Mwelwa, Ian
Mbewe, David
Simubali, Limonty
Jones, Christine M.
Chaponda, Mike
Coetzee, Maureen
Mulenga, Modest
Pringle, Julia C.
Shields, Tim
Curriero, Frank C.
Norris, Douglas E.
Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title_full Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title_fullStr Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title_full_unstemmed Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title_short Spatio-temporal heterogeneity of malaria vectors in northern Zambia: implications for vector control
title_sort spatio-temporal heterogeneity of malaria vectors in northern zambia: implications for vector control
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5031275/
https://www.ncbi.nlm.nih.gov/pubmed/27655231
http://dx.doi.org/10.1186/s13071-016-1786-9
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