Wild populations of malaria vectors can mate both inside and outside of human buildings

Nambunga, I. H. et al. (2021) Wild populations of malaria vectors can mate both inside and outside of human buildings. Parasites and Vectors, 14, 514. (doi: 10.1186/s13071-021-04989-8) (PMID:34620227) (PMCID:PMC8499572)

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Background: Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings. Method: Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps. Results: Proportions of inseminated females inside the experimental huts in the village increased from approximately  60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps. Conclusion: Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Ngowo, Halfan and Okumu, Professor Fredros and Ferguson, Professor Heather and Mshani, Mr Issa and Kahamba, Ms Najat
Authors: Nambunga, I. H., Msugupakulya, B. J., Hape, E. E., Mshani, I. H., Kahamba, N., Mkandawile, G., Mabula, D. M., Njalambaha, R. M., Kaindoa, E. W., Muyaga, L. L., Hermy, M. R.G., Tripet, F., Ferguson, H. M., Ngowo, H., and Okumu, F. O.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Parasites and Vectors
Publisher:BioMed Central
ISSN (Online):1756-3305
Copyright Holders:Copyright © 2021 The Authors
First Published:First published in Parasites and Vectors 14:514
Publisher Policy:Reproduced under a Creative Commons licence

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
309514Population biology and genomic studies of Anopheles funestus in TanzaniaHeather FergusonBill and Melinda Gates Foundation (GATES)INV-002138Institute of Biodiversity, Animal Health and Comparative Medicine
307462Integrating intervention targetable behaviours of malaria vectors to optimize interventions selection and impactHeather FergusonMedical Research Council (MRC)MR/T008873/1Institute of Biodiversity, Animal Health and Comparative Medicine