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.