Treatment With Antibiotics Drastically Reduces Importance of Flies as a Vector for Trachoma

Abstract

Abstract: : Purpose: Trachoma is the leading cause of infectious blindness worldwide. The WHO and public health agencies employ two major tactics in attempting to control the disease: eliminating the chlamydial infection that causes trachoma through antibiotics, and attempting to control the flies (Musca sorbens) that act as the vector for spread. It is now possible to assay the proportion of flies which harbor chlamydia. In this report, we determine how the prevalence of infection in children, and how treatment with antibiotics, affects carriage of chlamydia by flies. Methods: 120 flies were collected from the faces of 120 children in three villages that had received mass oral azithromycin distributions 6 months previously. 120 flies were also collected from 120 children in three untreated villages, randomly selected from the same pool as the treated villages. Roche Amplicor PCR kits were performed in a masked fashion to detect chlamydial DNA on the flies from both treated and untreated villages as previously described. Conjunctival swabs were also taken to assay for chlamydial prevalence in the children. Results: Chlamydia trachomatis was found on 23% of the flies in the untreated (control) villages, but only 0.3% of flies in the treated villages (P<0.001, Fisher’s exact). Furthermore, prevalence of trachoma in children proved to be an excellent predictor of the prevalence on flies in that village (correlation coefficient 0.8918) Conclusions: Not surprisingly, the prevalence of chlamydia on flies is correlated highly with the prevalence of chlamydial infection in children. At great cost, efforts are being made to reduce the prevalence of flies in trachoma endemic regions, however treating children with antibiotics drastically reduces the role of flies as a vector. Fly control may not be as necessary as previously thought, for effective trachoma control.

Keywords: trachoma • antibiotics/antifungals/antiparasitics • clinical (human) or epidemiologic studies: prevalence/incidence