| dc.description.abstract | Studies on the malaria parasite transmission, identification of vector-related
risk factors, and their relationships with the incidence of severe malaria in
children aged 1 to 4 years were undertaken in the the rural and peri-urban
areas around Kilifi District Hospital in the Coast Province of Kenya.
Intensive mosquito sampling in the rural area of Sokoke and Kilifi town for
one year through all-night human biting catches, elevated bednets, and day
resting indoor collections yielded three anopheline mosquitoes, namely,
Anopheles gambiae s.l., An. funestus and An. coustani. Of the three,
Anopheles gambiae s.l. was the most predominant and comprised 87.9% and
97.9% of the total collected at Sokoke and Kilifi town respectively. The
mosquitoes were examined tor Plasmodium falciparum parasite infections
by enzyme-linked immunosorbent assay (ELISA). The proportion of An.
gambiae s.l. with P. falciparum comprised 4.1% (20/491) at Sokoke village
and 2.2% (3/138)at Kilifi -town, indicating low infection rates. No sporozoite
infections were detected in An. [unestus and jn An. coustani suggesting that
their role in mala-ria transmission was minimal. Identification of the
members of the An. gambiae complex by the polymerase chain reaction
(PCR) technique revealed three species; An. gambiae s.s., An. arabiensie,
and An. meru.s. Together with An. 'funeetue, they form the malaria vectorial
system in Kilifi District.
Evaluation of entomological inoculation rates (EIR), which is calculated as
the product of the human-biting rate and the sporozoite rate, indicated that
residents were exposed to only 8.0 infective bites per year at Sokoke village
and 1.5 infective bites per year at Kilifi town. This implies that residents
at Sokoke are subjected to significantly more infective bites that their
counterparts at Kilifi town. Transmission of malaria in children aged 1to
4 years, the target group studied, was detected only during the months of
June to September and December to January at Sokoke and during
January, June and September at Kilifi town despite the fact that the
vectors were active throughout the year in both sites. Monthly patterns of
malaria transmission corresponded closely with the incidence of severe
infections. The yearly incidence of severe P. falciparum infections in this
age group of children was 24.1 per 1,000 children in Sokoke and 4.2 per
1,000 in Kilifi town. This ind,,icates that children at the rural site of Sokoke
frequently contract severe malaria infections than those at Kilifi town.
Blood meal samples were tested by the ELISA method for 534 An. gambiae
s.l. and 76 An. [u.nestus collected from 25 sites by light traps, aspiration
inside houses and pyrethrum spray collection.s. Human Immunoglobulin G
(IgG) was detected in 94.4% of the An. gambiae s.l and in 90.8% of the An.
funestus. No samples were positive for cow and only a few were positive for
goat the commonly kept livestock in the homes. Both species fed
predominantly on humans irrespective of availability of other hosts.
Inference was drawn that at these sites on the Kenya Coast, the high
degree of human-feeding by malaria vectors accounted for the efficiency of | en |
