Abstract
Background: Recent studies have observed vectors resting predominantly outdoors in settings where anti-vector tools are extensively deployed, attributed to selection pressure from use of control tools. This present study examined if the outdoor resting behaviour in the vector population is random or indicative of a consistent preference of one resting site over the other. Methods: Mark-release-recapture experiments were conducted with outdoor-resting Anopheles gambiae and An. funestus mosquitoes collected from two villages in northern Ghana during rainy and dry seasons. Mosquitoes were marked with fluorescent dyes and released indoors. The experiments were controlled with indoor-resting mosquitoes, which were marked and released outdoors. Species of all recaptured mosquitoes were identified and assessed for consistency in their resting behaviour. Results: A total of 4,460 outdoor-resting mosquitoes comprising An. gambiae sensu lato (s.l.) (2,636, 59%) and An. funestus complex (1,824, 41%) were marked and released. Overall, 31 (0.7%) mosquitoes were recaptured mostly from outdoor location comprising 25 (81%) An. gambiae s.l. and 6 (19%) An. funestus complex. Only 3 (10%) of the recaptured mosquitoes were found resting indoors where they were released. The majority of the outdoor-recaptured mosquitoes were An. arabiensis (11, 39%), followed by An. coluzzii (7, 25%); whereas all indoor-recaptured mosquitoes were An. coluzzii. For the control experiment, 324 indoor-resting mosquitoes constituting 313 (97%) An. gambiae s.l. and 11 (3%) An. funestus complex were marked and released. However, none of these was recaptured neither indoors nor outdoors. More mosquitoes were captured and recaptured during rainy season, but this was not statistically significant (Z=0.79, P=0.21). Conclusions: These results suggested the tendency for the mosquitoes to retain their outdoor-resting behaviour. Further investigations are required to ascertain if emerging preference for outdoor resting behaviour in malaria vector populations is consistent or a random occurrence.
Highlights
Vector control with indoor residual spraying (IRS) and longlasting insecticidal nets (LLINs) has contributed largely to reduction in malaria incidence and mortality[1]
Recent reports are indicating that vector control tools are inducing behavioural changes in mosquitoes such that some vector species have shifted from indoor-resting behaviour to resting outdoors
Northern Ghana has documented outdoor resting in An. gambiae sensu lato (s.l.) population[6,7] but it is not clear whether this behaviour only occurs randomly in the vector population. This present study examined if the preference for outdoor resting in the vector population was consistent or not
Summary
Vector control with indoor residual spraying (IRS) and longlasting insecticidal nets (LLINs) has contributed largely to reduction in malaria incidence and mortality[1]. Recent reports are indicating that vector control tools are inducing behavioural changes in mosquitoes such that some vector species have shifted from indoor-resting behaviour to resting outdoors (exophilic) This was as documented from studies in Ethiopia[5], Ghana[6,7], Kenya[8,9], Libreville[10] and Tanzania[11,12]. 324 indoor-resting mosquitoes constituting 313 (97%) An. gambiae s.l. and 11 (3%) An. funestus complex were marked and released. None of these was recaptured neither indoors nor outdoors. More mosquitoes were captured and recaptured during article can be found at the end of the article
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