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Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania.
Malar J. 2020 Jan 15; 19(1):22.MJ

Abstract

BACKGROUND

Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania.

METHODS

The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.-8 a.m.), evenings (6 p.m.-8 p.m.) and at night (11 p.m.-12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets).

RESULTS

Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus; 60-66% of An. arabiensis).

CONCLUSION

While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

Authors+Show Affiliations

Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. jbetwel@ihi.or.tz. School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania. jbetwel@ihi.or.tz.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. Centre for Biotechnology Research and Development, Kenya Medical Research Institute, Nairobi, Kenya.Amani Medical Research Centre, National Institute of Medical Research, Muheza, Tanzania.Environmental Health and Ecological Sciences Department, Ifakara Health Institute, P. O. Box 53, Ifakara, Tanzania. fredros@ihi.or.tz. School of Life Science and Bioengineering, The Nelson Mandela African Institution of Science and Technology, P. O. Box 447, Arusha, Tanzania. fredros@ihi.or.tz. School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. fredros@ihi.or.tz. Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, G12 8QQ, UK. fredros@ihi.or.tz.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31941508

Citation

Msugupakulya, Betwel J., et al. "Preferred Resting Surfaces of Dominant Malaria Vectors Inside Different House Types in Rural South-eastern Tanzania." Malaria Journal, vol. 19, no. 1, 2020, p. 22.
Msugupakulya BJ, Kaindoa EW, Ngowo HS, et al. Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania. Malar J. 2020;19(1):22.
Msugupakulya, B. J., Kaindoa, E. W., Ngowo, H. S., Kihonda, J. M., Kahamba, N. F., Msaky, D. S., Matoke-Muhia, D., Tungu, P. K., & Okumu, F. O. (2020). Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania. Malaria Journal, 19(1), 22. https://doi.org/10.1186/s12936-020-3108-0
Msugupakulya BJ, et al. Preferred Resting Surfaces of Dominant Malaria Vectors Inside Different House Types in Rural South-eastern Tanzania. Malar J. 2020 Jan 15;19(1):22. PubMed PMID: 31941508.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Preferred resting surfaces of dominant malaria vectors inside different house types in rural south-eastern Tanzania. AU - Msugupakulya,Betwel J, AU - Kaindoa,Emmanuel W, AU - Ngowo,Halfan S, AU - Kihonda,Japhet M, AU - Kahamba,Najat F, AU - Msaky,Dickson S, AU - Matoke-Muhia,Damaris, AU - Tungu,Patrick K, AU - Okumu,Fredros O, Y1 - 2020/01/15/ PY - 2019/11/28/received PY - 2020/01/07/accepted PY - 2020/1/17/entrez PY - 2020/1/17/pubmed PY - 2020/8/18/medline KW - An. arabiensis KW - An. funestus KW - Contact insecticides KW - House screening KW - Ifakara Health Institute KW - Indoor residual spraying KW - Indoor resting behaviours KW - Malaria vectors SP - 22 EP - 22 JF - Malaria journal JO - Malar J VL - 19 IS - 1 N2 - BACKGROUND: Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. METHODS: The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.-8 a.m.), evenings (6 p.m.-8 p.m.) and at night (11 p.m.-12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets). RESULTS: Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33-55% of An. funestus and 43-50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16-20% of An. funestus and 8-30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47-53% of An. funestus; 60-66% of An. arabiensis). CONCLUSION: While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs. SN - 1475-2875 UR - https://www.unboundmedicine.com/medline/citation/31941508/Preferred_resting_surfaces_of_dominant_malaria_vectors_inside_different_house_types_in_rural_south_eastern_Tanzania_ L2 - https://malariajournal.biomedcentral.com/articles/10.1186/s12936-020-3108-0 DB - PRIME DP - Unbound Medicine ER -