Abstract
BackgroundThe ecology of malaria vectors particularly in semi-arid areas of Africa is poorly understood. Accurate knowledge on this subject will boost current efforts to reduce the burden of malaria in sub-Saharan Africa. The objective of this study was to describe the dynamics of malaria transmission in two model semi-arid sites (Kamarimar and Tirion) in Baringo in Kenya.MethodsAdult mosquitoes were collected indoors by pyrethrum spray collections (PSC) and outdoors by Centers for Disease Control (CDC) light traps and identified to species by morphological characteristics. Sibling species of Anopheles gambiae complex were further characterized by rDNA. PCR and enzyme-linked immuno-sorbent assays (ELISA) were used to test for Plasmodium falciparum circumsporozoite proteins and host blood meal sources respectively.ResultsAnopheles arabiensis was not only the most dominant mosquito species in both study sites but also the only sibling species of An. gambiae s.l. present in the area. Other species identified in the study area were Anopheles funestus, Anopheles pharoensis and Anopheles coustani. For Kamarimar but not Tirion, the human blood index (HBI) for light trap samples was significantly higher than for PSC samples (Kamarimar, 0.63 and 0.11, Tirion, 0.48 and 0.43). The HBI for light trap samples was significantly higher in Kamarimar than in Tirion while that of PSC samples was significantly higher in Tirion than in Kamarimar. Entomological inoculation rates (EIR) were only detected for one month in Kamarimar and 3 months in Tirion. The number of houses in a homestead, number of people sleeping in the house, quality of the house, presence or absence of domestic animals, and distance to the animal shelter and the nearest larval habitat were significant predictors of An. arabiensis occurrence.ConclusionMalaria transmission in the study area is seasonal with An. arabiensis as the dominant vector. The fact this species feeds readily on humans and domestic animals suggest that zooprophylaxis may be a plausible malaria control strategy in semi-arid areas of Africa. The results also suggest that certain household characteristics may increase the risk of malaria transmission.
Highlights
The ecology of malaria vectors in semi-arid areas of Africa is poorly understood
A common challenge in these areas is the sudden shrinking or complete disappearance of the larval habitats during the dry season. This loss in larval habitats is followed by a rapid drop in abundance of malaria vectors and concomitant decrease in the incidence of severe malaria [2,3]
The study area is characterized by high temperatures and low rainfall (500-600 mm) conditions that lead to rapid loss of transient larval habitats
Summary
The ecology of malaria vectors in semi-arid areas of Africa is poorly understood. The onset of the rainy season results in surprisingly rapid increase in malaria vector populations [4,5,6] It is unclear whether the initial population buildup results from a new founder population of immigrants from neighboring areas with more permanent larval habitats or expansion from a very small local population that survives the dry period. Previous ecological studies suggest that Anopheles eggs have low tolerance to desiccation implying that only adults can survive the dry season [7]. These adults may hide in shelters such as rodent burrows, abandoned houses and wells, minimizing the chances of their detection through pyrethrum spray collections [8]. Despite local reduction in density during the dry season, population genetic studies suggest that An. arabiensis which is the most common vector in semi-arid areas, maintains large permanent deme over a large area [9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
