title: Plasmodium falciparum transmission and aridity: a Kenyan experience from the dry lands of Baringo and its implications for Anopheles arabiensis control.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Adult 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.
  
  
  RESULTS
  Anopheles 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.
  
  
  CONCLUSIONS
  Malaria 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.
authors.affiliation: Human Health Division, International Centre of Insect Physiology and Ecology, PO Box 30772-00100, Nairobi, Kenya. amala@icipe.org
authors.forename: Albert O
authors.initials: AO
authors.lastname: Mala
authors.forename: Lucy W
authors.initials: LW
authors.lastname: Irungu
authors.forename: Josephat I
authors.initials: JI
authors.lastname: Shililu
authors.forename: Ephantus J
authors.initials: EJ
authors.lastname: Muturi
authors.forename: Charles M
authors.initials: CM
authors.lastname: Mbogo
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Njagi
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Mukabana
authors.forename: John I
authors.initials: JI
authors.lastname: Githure
mesh_terms: D000818:Animals; D000852:Anopheles / Q000254:growth & development* / Q000469:parasitology*; D000953:Antigens, Protozoan / Q000032:analysis; D002980:Climate; D016054:DNA, Protozoan / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission*; D010963:Plasmodium falciparum / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction; D012621:Seasons
chemical_list: D000953:Antigens, Protozoan; D016054:DNA, Protozoan