Effects of improved water supply and sanitation on ascariasis, diarrhoea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma

Bull World Health Organ. 1991;69(5):609-21.


A total of 144 studies were analysed to examine the impact of improved water supply and sanitation facilities on ascariasis, diarrhoea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma. These 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 diarrhoea, trachoma, and ascariasis induced by water supplies and/or sanitation was 26%, 27%, and 29%, respectively; the median reduction for schistosomiasis and dracunculiasis 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 of ascariasis, diarrhoea, schistosomiasis, and trachoma. Sanitation facilities decreased diarrhoea morbidity and mortality and the severity of hookworm infection. Better water quality reduced the incidence of dracunculiasis, but its role in diarrhoeal disease control was less important than that of sanitation and hygiene.

PIP: Researchers reviewed 144 water and sanitation interventions conducted in various developing countries and in the US to look at the effect improved water supply and sanitation facilities had on ascariasis, diarrhea, dracunculiasis, hookworm infection, schistosomiasis, and trachoma. This review showed that improved water supply and sanitation facilities resulted in substantial reductions in morbidity of diarrhea (26%), ascariasis (29%), guinea worm infection (78%), schistosomiasis (77%), and trachoma (27%). Only 1 study of hookworm infection was not flawed and it demonstrated only a 4% reduction in incidence. Moreover accurate studies demonstrated a median reduction in diarrhea specific mortality of 65% and 55% in general child mortality. The researchers supposed that those studies that demonstrated reductions in morbidity for at least 1 disease did not give water and sanitation their complete due in improving health, especially those where 1 disease was prevalent in the intervention area. Some studies revealed that chemotherapy combined with improvement in water and sanitation prevented infection rates of some parasitic diseases from returning to pretreatment levels. Further the duration of infection fell 50% of the incidence or prevalence, e.g., ascariasis, schistosomiasis, and hookworm infection. Moreover, studies revealed reductions in childhood diarrhea and overall mortality were greater than diarrhea incidence or prevalence. Interventions which included improved excreta disposal and water quantity resulted in greater impacts than improvements in water quality. The review concluded with recommendations which included providing water as close to the home as possible to encourage use of large amounts of water for hygienic practices and hygiene education being integrated into water supply and health programs.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Ascariasis / epidemiology
  • Developing Countries
  • Diarrhea / etiology
  • Dracunculiasis / epidemiology
  • Hookworm Infections / epidemiology
  • Humans
  • Intestinal Diseases, Parasitic / epidemiology*
  • Intestinal Diseases, Parasitic / prevention & control
  • Sanitation*
  • Schistosomiasis / epidemiology
  • Trachoma / epidemiology
  • Water Supply / standards*