Protection of Sudanese irrigation workers from schistosome infections by a shift to earlier working hours.

Although schistosomiasis is an important occupational hazard for irrigation workers in Central Sudan, few measures have been found to protect them, short of abandoning the work. In an attempt to reduce their exposure to the large numbers of schistosome cercariae encountered in the water at midday, a group of Gezira canal cleaners were shifted to early morning working hours after being cured of their infections. They left the water each day at 10.00 hours, working from the canal banks thereafter. At the end of 6 months the prevalence of infections with Schistosoma mansoni was much lower in this group than in a similarly treated group with normal working schedules, indicating a practical way to protect irrigation and agricultural labourers.