• The risk of active trachoma in children appears to be higher in association with flies in the environment. However, a measure of fly density that could consistently be related to an increased risk of trachoma is unknown. In a survey of six villages in a hyperendemic area of Tanzania, a comparison was made between the number of flies on the faces (face-fly scores) of children and the number of household flies around the main door-ways (household-fly scores). The risk of trachoma associated with each measure was evaluated after adjusting for the age and sex of the child. A multiple logistic regression model demonstrated that the presence of files on the face was consistently associated with increased risk of trachoma, and that number of flies on the face is a superior predictor in terms of ease of measurement and strength of association than is number of household flies.
Brechner RJ, West S, Lynch M. Trachoma and FliesIndividual vs Environmental Risk Factors. Arch Ophthalmol. 1992;110(5):687-689. doi:10.1001/archopht.1992.01080170109035