Some aspects of malaria prevalence; vector infectivity and DDT resistance studies in Gambella region; South Western Ethiopia

ABSTRACT

Prevalence of plasmodium falciparum and plasmodium vivax in the human population; infectivity and DDT resistance of Anopheles mosquitoes were studied on samples collected during the peak malaria season of 1990 from Gambella; South West Ethiopia. Mosquito vectors collected were assorted into species and their infectivity with malaria parasites was determined by the enzyme-linked immunosorbent assay (ELISA). In the human population out of a total of 821 individuals examined from nine villages; 4.1 percent (34) were found to be positive for malaria parasites. Of the 34 positive individuals 5.9 percent (2) were positive for plasmodium vivax and 94.1 percent (32) for plasmodium falciparum. Although relatively high positivity rates for malaria were observed in 1-4 and 5-14 age groups; the difference in rates of positivity was not statistically significant for the whole population (p=0.5077). However; a significant difference in parasite prevalence was detected between the nine localities. Compared to that of 1989; the overall malaria prevalence rate in the human population significantly decreased in 1990. Insecticide susceptibilty studies revealed the presence of DDT resistant Anopheles gambiae s.l. mosquito in Itang. Furthermore; a strong evidence would suspect the vectorial status of A. pharoensis was obtained by detecting salivary gland sporozoite antigens of P. vivax in the head region of two mosquitos. Sporozoite rate of 0.76 percent (P. falciparum) for A. gambiae s.l. and 0.47 percent (P. vivax) for A. pharoensis were determined