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Open Access Research

Human exposure to anopheline mosquitoes occurs primarily indoors, even for users of insecticide-treated nets in Luangwa Valley, South-east Zambia

Aklilu Seyoum1*, Chadwick H Sikaala12, Javan Chanda2, Dingani Chinula2, Alex J Ntamatungiro3, Moonga Hawela2, John M Miller4, Tanya L Russell135, Olivier J T Briët67 and Gerry F Killeen13

Author Affiliations

1 Liverpool School of Tropical Medicine, Vector Group, Pembroke Place, Liverpool, L3 5QA, UK

2 National Malaria Control Centre, PO Box 32509, Lusaka, Zambia

3 Ifakara Health Institute, Biomedical and Environmental Thematic Group, Kiko Avenue, PO Box 78373, Dar es Salaam, Tanzania

4 PATH Malaria Control and Evaluation Partnership in Africa (MACEPA), National Malaria Control Centre, Lusaka, Zambia

5 James Cook University, Faculty of Medicine, Health and Molecular Sciences, Cairns, Australia

6 Swiss Tropical and Public Health Institute, Department of Public Health and Epidemiology, Basel, Switzerland

7 University of Basel, Basel, Switzerland

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Parasites & Vectors 2012, 5:101  doi:10.1186/1756-3305-5-101

Published: 30 May 2012

Abstract

Background

Current front line malaria vector control methods such as indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs), rely upon the preference of many primary vectors to feed and/or rest inside human habitations where they can be targeted with domestically-applied insecticidal products. We studied the human biting behaviour of the malaria vector Anopheles funestus Giles and the potential malaria vector Anopheles quadriannulatus Theobald in Luangwa valley, south-east Zambia.

Methods

Mosquitoes were collected by human landing catch in blocks of houses with either combined use of deltamethrin-based IRS and LLINs or LLINs alone. Human behaviour data were collected to estimate how much exposure to mosquito bites indoors and outdoors occurred at various times of the night for LLIN users and non-users.

Results

Anopheles funestus and An. quadriannulatus did not show preference to bite either indoors or outdoors: the proportions [95% confidence interval] caught indoors were 0.586 [0.303, 0.821] and 0.624 [0.324, 0.852], respectively. However, the overwhelming majority of both species were caught at times when most people are indoors. The proportion of mosquitoes caught at a time when most people are indoors were 0.981 [0.881, 0.997] and 0.897 [0.731, 0.965], respectively, so the proportion of human exposure to both species occuring indoors was high for individuals lacking LLINs (An. funestus: 0.983 and An. quadriannulatus: 0.970, respectively). While LLIN users were better protected, more than half of their exposure was nevertheless estimated to occur indoors (An. funestus: 0.570 and An. quadriannulatus: 0.584).

Conclusions

The proportion of human exposure to both An. funestus and An. quadriannulatus occuring indoors was high in the area and hence both species might be responsive to further peri-domestic measures if these mosquitoes are susceptible to insecticidal products.

Keywords:
Anopheles funestus; Anopheles quadriannulatus; Behaviour; Zambia