Malaria is a major problem in the Sudano-sahel Northeastern Nigeria with the
highest prevalence of malaria in pregnancy of 64.5 percent. Little is known about
the major malaria vector and its role in malaria transmission. Longitudinal
entomological and parasitological surveys were conducted to better understand the
relationship of the key components in malaria transmission dynamics .Anopheles
mosquitoes were sampled using pyrethroid spray collection and identified
morphologically and by molecular methods of Polymerase chain reaction (PCR).
Enzyme linked immunosorbent Assay (ELISA) was used for the bloodmeal analysis
and mosquito infectivity by circumsporozoite detection. Malariometric indices were
determined following the World Health Organization procedures. A total of 1030
female Anopheles mosquitoes were caught consisting of five species, namely, 1026
(99.6%) of Anopheles gambiae complex further identification using PCR showed
the predominant sibling species were An. arabiensis Patton 95%(n=221) and An.
gambiae s.s. 5%(n=12). Other Anopheles mosquitoes collected were
morphologically identified as An. pharoensis, An. squamosus and An. rhodesiense.
Results showed that the population of Anopheles arabiensis was significantly higher
than that of Anopheles gambiae s.s (P<0.05). Mosquito infection was determined
by ELISA method for the detection of Plasmodium falciparum sporozoites 7(2.4%)
were positive for P.falciparum circumsporozoite antigen. All seven were
An.arabiensis. Indoor collection was significantly higher than the outdoor collection
(P<0.01). Mosquito blood feeding source determined by direct ELISA showed
human bloodmeal was (98%, 94/96) for indoor collections and (2%, 2/96) for
outdoors (P<0.01). The Human Blood Index (HBI) was 0.98. The results implicate
xvi
An.arabiensis as the main malaria vector in the area. Of a total of 692 children
consecutively screened over a period of one year, significant difference (p<0.05) in
infection rates was observed between the males and the females. The levels of
parasitaemia asexual parasite were significantly related to age (p<0.05).The
majority of infected children (68.0%) were aged between 12-60 months and their
asexual parasite density was between 1000-5000 of whole blood. The month of
September recorded the highest geometric mean parasite density (GMPD) of
13,655 while the lowest parasite densities were observed during the dry season
months of March, April, and May while gametocytaemia was not significantly
affected by the age of the patients nor the season (p>0.05). Overall average
Inhibition of Emergence (IE) rates were 86% for the first week (0-7days) then
peaked to 100% during the second week (8-14days) and declined to 73% (15-
21days) on the third week and finally to 36% on the fourth week (22-28day).
Percentage Inhibition of Emergence between 0.1 and 0.5mg (a.i)/l treatments were
not different (P> 0.05). In planning effective site specific malaria vector control
programmes under the Integrated Vector Management (IVM) program of the
Federal Government of Nigeria, results of this study has highlighted the need to
give special consideration to the predominance of a single malaria vector An.
arabiensis in the Sudanosahel and the strong seasonality of malaria in contrast to
other regions of Nigeria. Findings also demonstrated the potentials of pyriproxyfen
as an effective mosquitoes larvicide for consideration under the Integrated Vector
Management (IVM) program for use in Sudanosahel Northeastern Nigeria.