The two schools studied were in the Ubiri and Kwam- sisi villages of the Tanga province of Northern Tanzania. Ubiri is situated in the foothills of the Usambara Mountains
at 2000 m above sea level. Kwamsisi, the other
village school surveyed, is sited near Korogwe and is at
an altitude of 500 m. The schools were chosen as they
offered contrasting locales, both of which were known,
on the basis of a previous pilot survey in June 1975, to
be associated with a high prevalence of parasitic infestation.
The schools were surveyed by a mobile team in
May 1976