Detection of Plasmodium sporozoites in Anopheles coustani s.l; a hindrance to malaria control strategies in highlands of western Kenya

Abstract

Re-emerging of high malaria incidences in highlands of western Kenya pose a challenge to malaria eradication efforts. Anopheles coustani is a sub-Saharan mosquito species implicated in transmission of malaria in many parts of Africa as a secondary vector. It is a zoo-anthropophilic species that has been assumed to be of negligible importance. A cross sectional study was carried out in April to June, 2020 in Eluche location, Mumias East sub-County, Kakamega County, Kenya to establish the contribution of Anopheles coustani in malaria transmission. Pyrethrum spray collections (PSC) and Centers for Disease Control (CDC) and prevention light traps were used for sampling mosquitoes. Mosquitoes were collected from both indoors; between 0700h and 1100h using PSC and outdoors between 1800h and 0700h using CDC light traps. All mosquitoes were identified morphologically and female Anopheles heads and thorax were analyzed further using Polymerase Chain Reaction (PCR) for Plasmodium sporozoite. A total of 188 female Anopheles mosquitoes were collected from both PSC and CDC light traps. This constituted of; 80(42.55%) An. coustani, 52(27.66%) An. funestus, 47(25.00%) An. maculipulpis, 8(4.26%) An. arabiensis and 1(0.53%) An. gambiae. Malaria sporozoite detection was done to all the Anopheles female mosquitoes but only two An. coustani tested positive for Plasmodium falciparum. In conclusion, Anopheles coustani plays a major role in outdoor malaria transmission in Mumias East Sub-County of Kakamega County in Western Kenya.