Background: The effective measures for the control of malaria and filariasis vectors can be achieved by targeting immature stages of anopheline and culicine mosquitoes in productive habitat. To design this strategy, the mechanisms (like biotic interactions with conspecifc and heterospecific larvae) regulating mosquito aquatic stages survivorship, development time and the size of emerging adults should be understood. This study explored the effect of co-habitation between An. gambiae s.s. and Cx. quinquefasciatus on different life history traits of both species under different densities and constant food supply in the habitats of the same size under semi-natural conditions. Methods. Experiments were set up with three combinations; Cx. quinquefasciatus alone (single species treatment), An. gambiae s.s. alone (single species treatment); and An. gambiae s.s. with Cx. quiquefasciatus (co-habitation treatment) in different densities in semi field situation. Results: The effect of co-habitation of An. gambiae s.s. and Cx. quinquefasciatus was found to principally affect three parameters. The wing-lengths (a proxy measure of body size) of An. gambiae s.s. in co-habitation treatments were significantly shorter in both females and males than in An. gambiae s.s single species treatments. In Cx. quinquefasciatus, no significant differences in wing-length were observed between the single species and co-habitation treatments. Daily survival rates were not significantly different between co-habitation and single species treatments for both An. gambiae s.s. and Cx. quinquefasciatus. Developmental time was found to be significantly different with single species treatments developing better than co-habitation treatments. Sex ratio was found to be significantly different from the proportion of 0.5 among single and co-habitation treatments species at different densities. Single species treatments had more males than females emerging while in co-habitation treatments more females emerged than males. In this study, there was no significant competitive survival advantage in co-habitation. Conclusion: These results suggest that co-habitation of An. gambiae s.s. and Cx. quinquefasciatus in semi-natural conditions affect mostly An. gambiae s.s. body size. Hence, more has to be understood on the effects of co-habitation of An. gambiae s.s. and Cx. quinquefasciatus in a natural ecology and its possible consequences in malaria and filariasis epidemiology. © 2012 Kweka et al; licensee BioMed Central Ltd.

Background: The effect of integrating vector larval intervention on malaria transmission is unknown when insecticide-treated bed-net (ITN) coverage is very high, and the optimal indicator for intervention evaluation needs to be determined when transmission is low. Methods. A post hoc assignment of intervention-control cluster design was used to assess the added effect of both indoor residual spraying (IRS) and Bacillus-based larvicides (Bti) in addition to ITN in the western Kenyan highlands in 2010 and 2011. Cross-sectional, mass parasite screenings, adult vector populations, and cohort of active case surveillance (ACS) were conducted before and after the intervention in three study sites with two- to three-paired intervention-control clusters at each site each year. The effect of larviciding, IRS, ITNs and other determinants of malaria risk was assessed by means of mixed estimating methods. Results: Average ITN coverage increased from 41% in 2010 to 92% in 2011 in the study sites. IRS intervention had significant added impact on reducing vector density in 2010 but the impact was modest in 2011. The effect of IRS on reducing parasite prevalence was significant in 2011 but was seasonal specific in 2010. ITN was significantly associated with parasite densities in 2010 but IRS application was significantly correlated with reduced gametocyte density in 2011. IRS application reduced about half of the clinical malaria cases in 2010 and about one-third in 2011 compare to non-intervention areas. Conclusion: Compared with a similar study conducted in 2005, the efficacy of the current integrated vector control with ITN, IRS, and Bti reduced three- to five-fold despite high ITN coverage, reflecting a modest added impact on malaria transmission. Additional strategies need to be developed to further reduce malaria transmission. © 2013 Zhou et al.; licensee BioMed Central Ltd.