Epidemiiology of Schistosohiasis in Bahir Dar
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Date
1988-06
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Addis Ababa University
Abstract
Various aspects of the epidemiology of schistosomiasis mansoni were
stuoieo for a period of one year at Bahir Dar \~ith the prime
o"bj ecti V0 of elucioating the transmission patterns.
Parasitological surveys revealed an overall prevalence of 12% among
residents of Kebeles 8, 9 and 10. More males ( 17%) than females
(8%) were infected ( P.(.O.Ol). The overall prevalence for school
children of Dil chibo anO Sertse Dengel were 32% and 45%, respectively.
School children yielded high annual incidence at the second survey
(February). Malacological findings suggested that Biomphalaria
pfeifferi snails peaked in density in September, towards the en6 of
the rainy season in Lake Tana ana in January, around the miadle of
the dry season at a site on the bank of the River Abay. In
September, infected snails were recovered from all collection sites.
Schistosome infection also developed in a relatively large number
of mice immersed in the month of September. In two series of
surveys, the major ~Iater contact activities were identified and it
was observed that there were diurnal and seasonal/variations in
these activities.
The study in general revealed that infection rates depend on age,
sel< and geographical location with respect to wat er body. Snail
population dynamics and associated schistosomal infection seem to
depend on rainfall and associated ecological changes. Incidence
studies, malacological findings and sentinel - mouse el<posure results
suggest that the main transmission season in Lake Tana is towards
the end and after rainy season. Intermittent transmission may also
take place throughout the year. Diurnal and seasonal variations in
human-water contact behaviours such as playing in \~ater of children,
bathing and swimming appear to have epidemiological significance in
the transmission of schistosomiasis.
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Biology