THE STATUS OF SCHISTOSOMA-MANSONI AND SNAIL HOSTS IN TIGRAY AND NORTHERN WELLO REGIONS, NORTHERN ETHIOPIA

A survey of Schistosoma mansoni infection and snail hosts was carried out in 1992 in six accessible schools and 11 water bodies respectively . Five to ten per cent of the students were randomly selected for stoo l examination by the Ritichie's method. In Adwa town, however, stools of 100 students out of the 199 selected were re-examined by Kato's met hod to assess intensity of infection. Results of stools examined by Ri tichie's method showed that S. mansoni positive patients were present in four out of six (66.7%) schools, the prevalence for school ranging from 1% in Maychew to 61.8% in Adwa. In all the localities, there was significant male preponderance in the prevalence of infection (p < 0.0 5). Among those whose stools were examined by the Kato's method in Adw a town, both prevalence and geometric mean egg count per gram of faece s (EPG) were highest in the 10 to 14 years age group reaching 68% and 597 followed by 64% and 591 respectively in the 15 to 19 years of age. Of the S. mansoni positive students in Adwa, 86% excreted 200 or more EPG, 84% of those in the 10 to 14 years of age excreted as high as 1, 600 EPG. Sexwise, no significant difference was observed in EPG (p > 0 .05). Biomphalaria pfeifferi, the principal snail host of S. mansoni i n Ethiopia, were collected from five out of the 11 waterbodies and wer e found shedding human schistosome cercariae in two of them, their inf ection rate reaching 0.7%. The ecological characteristics observed wer e found suitable for snail propagation. In this report, the need for d isease intervention in the endemic communities and the possible factor s attributable to the absence or low prevalence of intestinal schistos omiasis in others are discussed.