Anopheline mosquitoes behaviour and entomological monitoring in southwestern Ethiopia

Abstract

Background & objectives: Despite a tremendous expansion in the financing and coverage of malaria control programmes, the disease continues to be a global health threat. This study was conducted to assess the entomological parameters of anopheline mosquitoes, viz. species composition, abundance, longevity, behaviour and infectivity rates in Kersa district, Jimma zone, southwestern Ethiopia. Methods: Mosquito collection was carried out from each selected household in each of the nine selected study villages of Kersa district, using CDC light-traps and pyrethrum spray catches (PSCs) for seven months (June to December 2014). Mosquito count data were log transformed before analysis and the data were analyzed using SPSS software package version 16.0. Analysis of variance (ANOVA) was employed to compare means and Tukey’s post-hoc test was used for mean separation. Results: In total, 1559 adult female anopheline mosquitoes, representing at least three species were collected from the study villages. Of these, 1122 were collected by CDC light-traps and the rest 437 were collected by PSCs. Anopheles gambiae s.l. (71.8%) was the most abundant species, followed by An. coustani s.l. (22%) and An. pharoensis (6.2%). The mean monthly density of anopheline mosquito species was highly significant (p < 0.001). Significantly (p <0.05) higher population of An. gambiae s.l. were trapped indoor than outdoor. However, outdoor mean densities of An. pharoensis and An. coustani s.l. were significantly (p < 0.001) higher than indoor mean densities. The longevity of An. gambiae s.l. was higher in the months of June, July and August (mean 7.32 days) and lower in the months of October, November and December (mean 2.94 days). Two An. gambiae s.l. specimens were found positive for Plasmodium vivax 210 polymorphs and the overall infectivity rate was estimated to be 1.04%.