Is Mosquito Larval Source Management Appropriate for Reducing Malaria in Areas of Extensive Flooding in The Gambia? A Cross-over Intervention Trial

Abstract

Abstract. Larviciding to control malaria was assessed in rural areas with extensive seasonal flooding. Larval and adult mosquitoes and malaria incidence were surveyed routinely in four 100-km 2 areas either side of the Gambia River. Baseline data were collected in 2005. Microbial larvicide was applied to all water bodies by hand application with water-dispersible granular formulations and corn granules weekly from May to November in two areas in 2006 and in the other two areas in 2007 in a cross-over design. The intervention was associated with a reduction in habitats with late stage anopheline larvae and an 88% reduction in larval densities ( P < 0.001). The effect of the intervention on mosquito densities was not pronounced and was confounded by the distance of villages to the major breeding sites and year ( P = 0.002). There was no reduction in clinical malaria or anemia. Ground applications of non-residual larvicides with simple equipment are not effective in riverine areas with extensive flooding, where many habitats are poorly demarcated, highly mobile, and inaccessible on foot.

Evidence-based vector control? Improving the quality of vector control trials

“…While crossover trials may be suitable where the washout period is short (e.g., larvicide with a short half-life [66]), they should be used with caution where interventions are persistent (e.g., DDT, habitat manipulation).…”

Efficacy of indoor residual spraying with dichlorodiphenyltrichloroethane against malaria in Gambian communities with high usage of long-lasting insecticidal mosquito nets: a cluster-randomised controlled trial

“…A study cohort was used to assess the impact of the intervention on malaria with a lower age range of 6 months, since infants would be partly protected by maternal immunity, and the upper limit was selected since many older children would have developed immunity to infection [22][23][24][25] and it was also the age at which many children move to schools further away from their village. These children were randomly selected using statistical software (STATA version 11.0), stratified by age (<5 years, 5-10 years and >10 years) and weighted towards the younger children, who were less immune, at a ratio of 2:2:1 to achieve a total of 7845 with an average of 111/cluster (range 65-213) (Figure 2).…”

Microbial larvicides for mosquito control: Impact of long lasting formulations of Bacillus thuringiensis var. israelensis and Bacillus sphaericus on non‐target organisms in western Kenya highlands

“…Thus, the toxins responsible for the pathogenic effect in mosquito larvae have no effect to vertebrates and some invertebrates, and hence they are suitable for application even in peri‐domestic mosquito breeding habitats (Lacey, 2007; Lacey & Merritt, 2003; Saik, Lacey, & Lacey, 1990). However, the conventional Bti and Bs have low residual activity and require repeated applications, which increase the cost of interventions (Fillinger, Knols, & Becker, 2003; Majambere, Lindsay, Green, Kandeh, & Fillinger, 2007; Majambere et al., 2010). In the recent past, long lasting microbial larvicide formulations that combine both Bti and Bs with potential for sustained release of active ingredients for up to 6 months have become available (Afrane et al., 2016; Zhou et al., 2016).…”