| dc.description.abstract | This study was conducted in Kakstngrt location west of llomabay
and south of Mbita point. It is located in Mbita division, South Nyanza
district, Nyanza province, Kenya
The general objectives of the study centred around comparing the
potent ials of malaria transmission by Anopheles species between lwo sites
located close to each other, but with different Anoplteles breeding
charactertsttcs. Anopheles species found in the study area were
idenUfled, their seasonal abundancies det ermlned. infection rates
measured, and an attempt to determine their vector bionomics was made.
In addition, nonhuman hosts for these vectors were idenUfled. Malaria
infection rates in the human population were also examined.
Anopheles larval habitats were more directly dependent on rainfall
at the inland site, Kaksingri East (1\:E), than at the lakeshore site,
Kaksingri West (KW). In all collections, first instars predominated and
pupae were the least found- KW represented a more stable larval breeding
situation than RE. The lake played a....,'ifc~joror le in the breeding of ~~
mosquitoes ill the study sites.
Five Anopheles species, An. oicbtensis. An. qainbiae, An. [unestus,
Al1. ptiaroensis, and An. ziemanlli were Idenulled at KW, while at KE, only
3 species were fourid: - An. arabierisis, Alt. gambiae and An. Juneslus. An.
gambiae was the most abundant species taken by aJl collection techniques,
from both sltes. Species idenUflcation following DNA amplification by
polymerase chain reaction (peR) showed that Art. arabiertSis and An.
gambiae were the only members of the An. gambiae s.l. complex present
in the two study areas.
There was a remarkable difference in the distribution of mosquito
species between the two sites. The relative abundance of An. gambiae
compared to An. arabiensis was higher in KE than in KW. Monthly
population densities per house of An. arabiensis and An. gambiae were
significantly different between the two sites. An. funestus was found in
higher densities in KW than in KE, and comparison between sites was not
possible for this species. Lagged total monthly rainfall was significantly
correlated to the house resting density of An. arabiensis and An. gambiae
in both sites. An. funestus showed positive but not significant correlation
to the rainfall, in this site.
Night biting collections were only analysed for KW, because only a
few specimen were captured at KE. For KW, there were seasonal
differences in the night biting rates between species. An. funestus was
biting more at night in August to November 1991, and by March to April
1992, this species was not found at all. An. gambiae on the other hand
showed lower night biting rates in the period August to Novermber 1991,
and highest in March to April 1992.
~'" ....••.•.. ...,
The only hosts for Anopheles::;'mosquitoes identified in the study
areas were humans and bovids. From brood meals smeared on filter
papers, tests on other hosts were negative. From blood meal pellets, An.
arabiensis and An. gambiae were more anthropophilic in both sites. An.
- funestus caught in KWwere more zoophilic, based, however, on very little
data. Feeding patterns were however different between the three
Anopheles species within sites. Feeding patterns between sites were
similar.
An. arabiensis and An. funestus were negative for P. falciparum
Circumsporozoite Protein (P.falciparum CSP) by Enzyme Linked
immunosorbent Assay (ELISA)in KE. In the same site, An. gambiae
infection rates by ELISA were generally high, and the peak followed the
long rains. In KW, An. gambiae showed the same pattern of infection as in
KE. In KW, An. arabiensis was infected more at the end of the two rainy
seasons. Plasmodium infection rates by ELISA were significantly higher
in KE than in KW. Sporozoites were not found by dissection in either site.
Parasitological investigations showed that the two study sites are
malaria endemic areas. Prevalence rates were high in both sites ranging
above 94% in children and above 80% in adults. There were high
gametocyte rates in both age groups in both sites. which increased the
chances of infecting feeding mosquitoes.
This study showed a difference in the malaria transmission
potentials between the two sites. It is more risky to reside a short
distance inland as opposed to residing on the lake shore itself | en |
