Infectivity rates of vectors of bancroftian filariasis during wet and dry seasons in Malindi and Kwale Districts of Coast Province, Kenya.
Abstract
Bancroftianfilariasis, a disease caused by Wuchereria bancrofti, is on the increase on the
Kenyancoast with an estimated 2.5 million people at the risk of infection. 'Endemic zones
on the Kenyan coast are Malindi, Kwale, Lamu, Tana River and Kilifi districts. Control of
the ,disease is possible by chemotherapy , vector control and vector/man contact.
avoidance. For effective vector control and vector / man avoidance in Kenya, there is
needfor more enviromental and weather specific vector studies in the endemic zones.
Suchstudies include enquiry in to the seasonal variation in infectivity rates of important
vector species in a specified area so as to know when to protect oneself from infective
mosquitobites and when it is most important to control the vector. This was the main issue
of concern of this research.
Two study sites on the Kenyan coast known to have bancroftian filariasis were selected.
These were Gazi in Kwale district and Madunguni in Malindi district. Houses and
compounds from which mosquitoes were to be sampled were selected by simple random
sampling. Three methods of mosquito collection were employed; Day resting indoor
collection [DRI], Pyrethrum spray catch [PSC] and light traps. The mosquitoes collected
were morphologically sorted out into species , females dissected and any Wuchereria
bancrofti third stage larvae present recorded. A total of 1832 female mosquitoes were
dissected in this study in two phases, the the transmission [wet] season and the nontransmission
[dry] season.
A significant difference [x2 =3.05 in Madunguni and 6.18 in Gazi,P<0.05] was found in the
vector infectivity rates between the two seasons. The difference was greater in Gazi whose
infectivity rate was zero during the non-transmission period than Madunguni whose
infectivity rate was 0.21% during the same period. Anopheles gambiae 5.1 was the main
vector in both study sites. The others were Culex quinquefasciatus and Anopheles
funestus in order of importance. It was concluded that there is a difference in infectivity
rates of bancroftian filariasis vectors between the transmission season and the nontransmission
season. The abundance of An. gambiae s.s during the transmission season
could be responsible for the increased infectivity rates of vectors in this season.
*The wet and dry seasons in this thesis are specific for the year 1998 due to the EI Nino
effect. The dry season in this case was in October and September whereas the wet
season was in June and July 1998.
Citation
Sichangi, K(1999). Infectivity rates of vectors of bancroftian filariasis during wet and dry seasons in Malindi and Kwale Districts of Coast Province, Kenya.Publisher
Department of Medicine, University of Nairobi
Subject
VectorsBancroftian filariasis
Wet and dry seasons
Malindi District
Kwale District
Coast Province
Kenya
Description
Msc Thesis