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New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania

Background: Malaria mosquitoes form mating swarms around sunset, often at the same locations for months or years. Unfortunately, studies of Anopheles swarms are rare in East Africa, the last recorded field observations in Tanzania having been in 1983. Methods: Mosquito swarms were surveyed by traine...

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Autores principales: Kaindoa, Emmanuel W., Ngowo, Halfan S., Limwagu, Alex, Mkandawile, Gustav, Kihonda, Japhet, Masalu, John Paliga, Bwanary, Hamis, Diabate, Abdoulaye, Okumu, Fredros O.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: F1000 Research Limited 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5691375/
https://www.ncbi.nlm.nih.gov/pubmed/29184918
http://dx.doi.org/10.12688/wellcomeopenres.12458.1
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author Kaindoa, Emmanuel W.
Ngowo, Halfan S.
Limwagu, Alex
Mkandawile, Gustav
Kihonda, Japhet
Masalu, John Paliga
Bwanary, Hamis
Diabate, Abdoulaye
Okumu, Fredros O.
author_facet Kaindoa, Emmanuel W.
Ngowo, Halfan S.
Limwagu, Alex
Mkandawile, Gustav
Kihonda, Japhet
Masalu, John Paliga
Bwanary, Hamis
Diabate, Abdoulaye
Okumu, Fredros O.
author_sort Kaindoa, Emmanuel W.
collection PubMed
description Background: Malaria mosquitoes form mating swarms around sunset, often at the same locations for months or years. Unfortunately, studies of Anopheles swarms are rare in East Africa, the last recorded field observations in Tanzania having been in 1983. Methods: Mosquito swarms were surveyed by trained volunteers between August-2016 and June-2017 in Ulanga district, Tanzania. Identified Anopheles swarms were sampled using sweep nets, and collected mosquitoes killed by refrigeration then identified by sex and taxa. Sub-samples were further identified by PCR, and spermatheca of females examined for mating status. Mosquito ages were estimated by observing female ovarian tracheoles and rotation of male genitalia. GPS locations, types of swarm markers, start/end times of swarming, heights above ground, mosquito counts/swarm, and copulation events were recorded. Results: A total of 216 Anopheles swarms were identified, characterized and mapped, from which 7,142 Anopheles gambiae s.l and 13 Anopheles funestus were sampled. The An. gambiae s.l were 99.6% males and 0.4% females, while the An. funestus were all males. Of all An. gambiae s.l analyzed by PCR, 86.7% were An. arabiensis, while 13.3% returned non-amplified DNA. Mean height (±SD) of swarms was 2.74±0.64m, and median duration was 20 (IQR; 15-25) minutes. Confirmed swarm markers included rice fields (25.5%), burned grounds (17.2%), banana trees (13%), brick piles (8.8%), garbage heaps (7.9%) and ant-hills (7.4%). Visual estimates of swarm sizes by the volunteers was strongly correlated to actual sizes by sweep nets (R=0.94; P=<0.001). All females examined were nulliparous and 95.6% [N=6787] of males had rotated genitalia, indicating sexual maturity. Conclusions: This is the first report of Anopheles swarms in Tanzania in more than three decades. The study demonstrates that the swarms can be identified and characterized by trained community-based volunteers, and highlights potential new interventions, for example targeted aerosol spraying of the swarms to improve malaria control.
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spelling pubmed-56913752017-11-28 New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania Kaindoa, Emmanuel W. Ngowo, Halfan S. Limwagu, Alex Mkandawile, Gustav Kihonda, Japhet Masalu, John Paliga Bwanary, Hamis Diabate, Abdoulaye Okumu, Fredros O. Wellcome Open Res Research Article Background: Malaria mosquitoes form mating swarms around sunset, often at the same locations for months or years. Unfortunately, studies of Anopheles swarms are rare in East Africa, the last recorded field observations in Tanzania having been in 1983. Methods: Mosquito swarms were surveyed by trained volunteers between August-2016 and June-2017 in Ulanga district, Tanzania. Identified Anopheles swarms were sampled using sweep nets, and collected mosquitoes killed by refrigeration then identified by sex and taxa. Sub-samples were further identified by PCR, and spermatheca of females examined for mating status. Mosquito ages were estimated by observing female ovarian tracheoles and rotation of male genitalia. GPS locations, types of swarm markers, start/end times of swarming, heights above ground, mosquito counts/swarm, and copulation events were recorded. Results: A total of 216 Anopheles swarms were identified, characterized and mapped, from which 7,142 Anopheles gambiae s.l and 13 Anopheles funestus were sampled. The An. gambiae s.l were 99.6% males and 0.4% females, while the An. funestus were all males. Of all An. gambiae s.l analyzed by PCR, 86.7% were An. arabiensis, while 13.3% returned non-amplified DNA. Mean height (±SD) of swarms was 2.74±0.64m, and median duration was 20 (IQR; 15-25) minutes. Confirmed swarm markers included rice fields (25.5%), burned grounds (17.2%), banana trees (13%), brick piles (8.8%), garbage heaps (7.9%) and ant-hills (7.4%). Visual estimates of swarm sizes by the volunteers was strongly correlated to actual sizes by sweep nets (R=0.94; P=<0.001). All females examined were nulliparous and 95.6% [N=6787] of males had rotated genitalia, indicating sexual maturity. Conclusions: This is the first report of Anopheles swarms in Tanzania in more than three decades. The study demonstrates that the swarms can be identified and characterized by trained community-based volunteers, and highlights potential new interventions, for example targeted aerosol spraying of the swarms to improve malaria control. F1000 Research Limited 2017-09-22 /pmc/articles/PMC5691375/ /pubmed/29184918 http://dx.doi.org/10.12688/wellcomeopenres.12458.1 Text en Copyright: © 2017 Kaindoa EW et al. http://creativecommons.org/licenses/by/4.0/ This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Article
Kaindoa, Emmanuel W.
Ngowo, Halfan S.
Limwagu, Alex
Mkandawile, Gustav
Kihonda, Japhet
Masalu, John Paliga
Bwanary, Hamis
Diabate, Abdoulaye
Okumu, Fredros O.
New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title_full New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title_fullStr New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title_full_unstemmed New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title_short New evidence of mating swarms of the malaria vector, Anopheles arabiensis in Tanzania
title_sort new evidence of mating swarms of the malaria vector, anopheles arabiensis in tanzania
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5691375/
https://www.ncbi.nlm.nih.gov/pubmed/29184918
http://dx.doi.org/10.12688/wellcomeopenres.12458.1
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