Esrey, S.A., "Effects of improved water supply and sanitation on
ascariasis, diarrhea, dracunculiasis, hookworm infection, schistomiasis,
and trachoma." Bulletin of the World Health Organization 69 (5) 1991: 609-621 A Total of 144 studies were analyzed to examine the impact of improved water supply
and sanitation facilities on ascariasis, diarrohoea, dracunculiasis,
hookworm infection, schistosomiasis, and trachoma. Those diseases were
selected because they are widespread and illustrate the variety of mechanisms
through which improved water and sanitation can protect people.
Disease-specific median reduction levels were calculated for all studies,
and separately for the more methodologically rigorous ones. For the latter
studies, the median reduction in morbidity for diarrohoea, trachoma and
ascariasis, induced by water supplies and/or sanitation was 26%, 27%, and 29%
respectively; the median reduction for dracunculiasis, and schistosomiasis,
was higher at 77% and 78% respectively. All studies of hookworm infection
were flawed, apart from one, which reported a 4% reduction in incidence. For hookworm infection, ascariasis, and schistosomiasis, the reduction in
disease severity, as measured in egg counts, was greater than that in incidence
or prevalence. Child mortality fell by 55%, which suggests that water and
sanitation have a substantial impact on child survival. Water for personal and domestic hygiene was important in reducing the rates
for ascariasis, diarrhea, schistosomiasis, and trachoma. Sanitation facilities
decreased diarrhea morbidity and mortality, and the severity of hookworm infection.
Better water quality reduced the incidence of dracunculiasis, but its role
in diarrheal disease control was less important than that of
sanitation and hygiene.