Optimising a Resting box to enhance Adult Gravid Female Mosquitoe Auto-disseminate Larvicide in a Semi field

Abstract

Malaria control strategies that target adult mosquitoes are challenged by the emergence of insecticide resistance and behavioral changes of vectors. The conventional approach of applying larvicides is limited by high operational costs and inadequate knowledge of mosquito breeding habitats especially in rural African communities. This study developed a potential mosquito contamination site, assessed the potential of adult female Anopheles gambiae s.s to pick up fluorescent dye and auto dissemination from resting box to their breeding habitats. A screened semi-field system (SFS) with and without a mud hut inside were used to evaluate the efficacy of a designed mosquito resting box for delivery of fluorescent dye to resting mosquitoes and subsequent auto dissemination to artificial habitats within the SFS. Mud hut was used as a replica of the community housing. Coloured cotton fabric (red, black, blue, white) were evaluated for resting preference inside and outside the hut. Different box sizes and shapes were designed, with an inner lining using preferred fabric colour. Laboratory reared blood fed An. gambiae were released in the SFS to establish the preferred resting box size, colour and shape. The effective cardboard box2 nd design (CB-2) was then dusted with 5g of non-toxic red fluorescent dye, in which mosquitoes were released nearby the box, examined to ensure they entered the box, and allowed mosquito to locate habitat. The visitation rate at larval sites was examined using an OviART gravid trap. Trapped mosquitoes were removed daily, examined for dust contamination and recorded. Black fabric generally had a high resting preference of 60%.CB-3(Rectangular shaped cardboard-3 rd design) lined with black fabric had a higher percentage resting preference (61%) compared to red fabric lined box of similar design (39%).The box shape experiment revealed that rectangular box of dimension 45cmL×30cmL×45cmH had a significantly resting preference with a mean resting rate of 74.0 ± 4.406 compared to circular box (51.0 ± 3.947) of similar size, the difference was significant (F= 14.899, df= 1, P= 0.001). Auto dissemination demonstration showed a high proportion of mosquito visiting a Cedrol treated habitat 58(50.49-65.51) compared to control/tap water site 36 (29.05-42.62). In all the recaptured mosquitoes in both treated and control site, high proportion had full dye 39 (33.55-43.79) and a few, partial dye 19 (14.20-24.46). This was an indication of successful transfer of dye from the box to mosquito and from mosquito to oviposition site showing a possibility of mosquitoes to transfer lethal dose to the larval site. This study provides a proof of auto dissemination principle of using adult female An. gambiae to transfer chemical from effective passive contamination station to malaria vector habitat. The finding shade light on the potential of this approach to target and control immature stages of malaria vectors (An, gambiae s.s). Field studies using novel adulticides and larvicides are recommended to evaluate the utility of the MRB as a mosquito control tool for the management of malaria.