Human exposure to anopheline mosquitoes occurs primarily indoors, even for users of insecticide-treated nets in Luangwa Valley, South-east Zambia.
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.
Liverpool School of Tropical Medicine, Vector Group, Pembroke Place, Liverpool L3 5QA, UK. aklilus@yahoo.com
Aklilu
A
Seyoum
Chadwick H
CH
Sikaala
Javan
J
Chanda
Dingani
D
Chinula
Alex J
AJ
Ntamatungiro
Moonga
M
Hawela
John M
JM
Miller
Tanya L
TL
Russell
Olivier J T
OJ
Briët
Gerry F
GF
Killeen
D000818:Animals; D000852:Anopheles / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D006798:Housing; D006801:Humans; D007299:Insect Bites and Stings / Q000517:prevention & control; D007303:Insect Vectors / Q000502:physiology; D057148:Insecticide-Treated Bednets / Q000706:statistics & numerical data*; D008288:Malaria / Q000517:prevention & control / Q000635:transmission; D009032:Mosquito Control; D012307:Risk Factors; D015024:Zambia