Impact of fly control on childhood diarrhoea in Pakistan: community-randomised trial

Background Several million children are killed each year by diarrhoeal dise ases; preventive strategies appropriate for developing countries are vital. Despite strong circumstantial evidence that flies are vectors of diarrhoea l diseases, no convincing studies of the impact of fly control on diarrhoea incidence in developing countries have been reported. We undertook a rando mised study of the effect of insecticide spraying on diarrhoea incidence. Methods Six study villages were randomly assigned to two groups. Flies were controlled through insecticide application in group A in 1995 and in group B in 1996. In 1997 the effectiveness of baited fly traps was tested in gro up A villages. Diarrhoea episodes were monitored in children under 5 years through mothers' reports during weekly visits by a health visitor. Fly dens ity was monitored by use of sticky fly-papers hung in sentinel compounds. Findings During the fly seasons (March-June) of both 1995 and 1996, insecti cide application practically eliminated the fly population in the treated v illages. The incidence of diarrhoea was lower in the sprayed villages than in the unsprayed villages in both 1995 (mean episodes per child-year 6.3 vs 7.1) and 1996 (4.4 vs 6.5); the reduction in incidence was 23% (95% CI 11- 33, p=0.007). At times other than the fly season there was no evidence of a difference in diarrhoea morbidity between sprayed and unsprayed villages. Fly density data for 1997 indicate the ineffectiveness of baited traps in t his setting. Interpretation Fly control can have an impact on diarrhoea incidence simila r to, or greater than, that of the interventions currently recommended by W HO for inclusion in diarrhoeal disease control programmes in developing cou ntries. This important finding needs confirmation in other settings in deve loping countries. Technologies and practices that interrupt disease transmi ssion by flies need to be developed and promoted.