Journal of Vector Borne Diseases (Sep 2009)
Seasonal changes of infectivity rates of Bancroftian filariasis vectors in coast province, Kenya
Abstract
Background & objectives: Bancroftian filariasis in Kenya is endemic in coastal districts with anestimated number of 2.5 million people at risk of infection. The main mosquito genera involved intransmission of Wuchereria bancrofti in these areas are Anopheles, Culex and Mansonia. Thestudy was envisaged to compare the infectivity rates of Bancroftian filariasis vectors between thehigh transmission (wet) and the low transmission (dry) seasons.Methods: Mosquitoes were sampled from houses and compounds from two study sites, Gazi andMadunguni, 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 mosquitoeswere dissected to search for W. bancrofti III stage larvae.Results: A total of 1832 female mosquitoes were dissected. Infectivity rates of vectors in Madunguniwere 1.49 and 0.21% in wet and dry seasons respectively, whereas in Gazi, these were 1.69 and0%, respectively. There was a significant difference in the infectivity rates between the two seasonsin both Madunguni and Gazi villages (p <0.05). Anopheles gambiae s.l. was the main vector inboth study sites followed by Culex quinquefasciatus and An. funestus.Conclusion: There was a difference in infectivity rates of Bancroftian filariasis vectors betweenthe wet and dry seasons. The abundance of An. gambiae s.s. during the transmission season couldbe responsible for the increased infectivity rates of vectors in this season.
