Seasonal changes of infectivity rates of Bancroftian filariasis vectors in coast province, Kenya.

Abstract

J Vector Borne Dis 46, September 2009, pp. 219–224 Seasonal changes of infectivity rates of Bancroftian filariasis vectors in coast province, Kenya Sichangi Kasili a , Florence Oyieke b , C. Wamae c & Charles Mbogo d a Department of Zoology, Jomo Kenyatta University of Agriculture and Technology, Nairobi; b School of Biological Sciences, University of Nairobi, Nairobi; c Centre for Microbiology Research, Kenya Medical Research Institute, Nairobi, d Centre for Geographic Medical Research-Coast, Kenya Medical Research Institute, Nairobi, Kenya Abstract Background & objectives: Bancroftian filariasis in Kenya is endemic in coastal districts with an estimated number of 2.5 million people at risk of infection. The main mosquito genera involved in transmission of Wuchereria bancrofti in these areas are Anopheles, Culex and Mansonia . The study was envisaged to compare the infectivity rates of Bancroftian filariasis vectors between the high transmission (wet) and the low transmission (dry) seasons. Methods: Mosquitoes were sampled from houses and compounds from two study sites, Gazi and Madunguni, on the Kenyan coast. Day resting indoor collection (DRI), pyrethrum spray catch (PSC) and CDC light traps were used to collect mosquitoes. After identification, female mosquitoes were dissected to search for W. bancrofti III stage larvae. Results: A total of 1832 female mosquitoes were dissected. Infectivity rates of vectors in Madunguni were 1.49 and 0.21% in wet and dry seasons respectively, whereas in Gazi, these were 1.69 and 0%, respectively. There was a significant difference in the infectivity rates between the two seasons in both Madunguni and Gazi villages (p <0.05). Anopheles gambiae s.l. was the main vector in both study sites followed by Culex quinquefasciatus and An. funestus . Conclusion: There was a difference in infectivity rates of Bancroftian filariasis vectors between the wet and dry seasons. The abundance of An. gambiae s.s. during the transmission season could be responsible for the increased infectivity rates of vectors in this season.