Abstract:
Background
An. funestus is a major Afrotropical vector of human malaria. This study sought to investigate
the larval ecology, sporozoite infection rates and blood meal sources of An. funestus in
western Kenya.
Methods
Larval surveys were carried out in Bungoma (Highland) and Kombewa (lowland) of western
Kenya. Aquatic habitats were identified, characterized, georeferenced and carefully examined
for mosquito larvae and predators. Indoor resting mosquitoes were sampled using
pyrethrum spray catches. Adults and larvae were morphologically and molecularly identified
to species. Sporozoite infections and blood meal sources were detected using real-time
PCR and ELISA respectively.
Results
Of the 151 aquatic habitats assessed, 62/80 (78%) in Bungoma and 58/71(82%) in Kombewa
were positive for mosquito larvae. Of the 3,193 larvae sampled, An. funestus larvae
constitute 38% (1224/3193). Bungoma recorded a higher number of An. funestus larvae
(85%, 95%, CI, 8.722–17.15) than Kombewa (15%, 95%, CI, 1.33–3.91). Molecular identification
of larvae showed that 89% (n = 80) were An. funestus. Approximately 59%, 35% and
5% of An. funestus larvae co-existed with An. gambiae s.l, Culex spp and An. coustani in
the same habitats respectively. Of 1,221 An. funestus s.l adults sampled, molecular identifications revealed that An. funestus constituted 87% (n = 201) and 88% (n = 179) in
Bungoma and Kombewa, respectively. The Plasmodium falciparum sporozoite rate of An.
funestus in Bungoma and Kombewa was 2% (3/174) and 1% (2/157), respectively, and the
human blood index of An. funestus was 84% (48/57) and 89% (39/44) and for Bungoma and
Kombewa, respectively.
Conclusion
Man-made ponds had the highest abundance of An. funestus larvae. Multiple regression
and principal component analyses identified the distance to the nearest house as the key
environmental factor associated with the abundance of An. funestus larvae in aquatic habitats.
This study serves as a guide for the control of An. funestus and other mosquito species
to complement existing vector control strategies.
