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

Since circumstantial evidence suggests that flies are vectors of diarrheal diseases, a randomized study of the effect of insecticide spraying upon the incidence of diarrhea was conducted near the town of Peshawar, North West Frontier Province, Pakistan. 6 study villages were randomly assigned to 2 groups, with flies controlled through the twice weekly application of ultra low volume space spraying with insecticide in group A in 1995 and in group B in 1996. The insecticide used was Aqua K-Othrine, a water-based formulation of deltamethrin, applied at a dose of 0.5-1.0 g of active ingredient per hectare by Porta-Pak sprayers. In 1997, the effectiveness of baited fly traps was tested in group A villages. The incidence of diarrhea episodes was monitored in children under age 5 years through mothers' reports during weekly visits by a health worker, and fly density was monitored using sticky fly-papers hung in sentinel compounds. During the fly seasons of March-June in 1995 and 1996, the application of insecticide almost eliminated the fly population in the treated villages. The incidence of diarrhea was lower in the sprayed villages than in the unsprayed villages in both 1995 and 1996, for an overall 23% reduction in incidence. At times other than the fly season, no evidence was observed of a difference in diarrhea morbidity between sprayed and unsprayed villages. Fly density data for 1997 found the baited traps to be ineffective.