Preliminary evidence that synanthropic fl ies contribute to the transmission of trachoma- causing Chlamydia trachomatis in Latin America Evidência preliminar que moscas sinantrópicas contribuem à transmissão de Chlamydia trachomatis causando tracoma na América Latina

Synanthropic flies have been shown to be important mechanical vectors of Chlamydia trachomatis, which causes trachoma. However entomological studies have not been forthcoming in Latin America. This study assesses the relationship between household dipteran fly densities and active childhood trachoma in a village on Marajó Island, Pará state, Brazil. For 78 households, members were examined for signs of trachoma, relative abundance of potential trachoma vectors (Diptera, Chloropidae and Diptera, Muscidae) was quantified by trap counts, and additional measures of household hygiene associated with C. trachomatis transmission were assessed. Active childhood trachoma prevalence was 24.1% (45/187), present in 46.2% of sampled households with evidence of case clustering. Childhood prevalence was positively associated with increased fly densities, whereas indirect measures of sanitary conditions (latrine ownership and perceived importance of flies) showed a protective effect. This study indicates that C. trachomatis can be transmitted by synanthropic flies in this region of Latin America. Trachoma; Chlamydia trachomatis; Disease Vectors Introduction Successful reductions in trachoma caused by Chlamydia trachomatis have recently been achieved in the Gambia by reducing the density of the filth fly Musca sorbens (Wiedemann), which constitutes an important arthropod vector along with the house fly Musca domestica in Africa 1,2,3, and the bush fly Musca vetustissima (Walker) in Australia 4. In hyperendemic regions in Latin America, where childhood case prevalences are comparable to those in Africa and Asia 5,6, few epidemiological studies have been conducted, and to our knowledge none have investigated the potential role of synanthropic eye-seeking flies in Chlamydia transmission (M. sorbens does not occur in Latin America). In addition to Musca spp., eyegnats (Hippelates spp. and Liohippelates spp.) are likely to constitute an important vector group since like M. sorbens they swarm around eyes and bodily secretions 7 and can transmit Brazilian purpuric fever, for which the initial symptom is an acute conjunctivitis 8. This study aims (i) to quantify the relative abundance (measured by trap counts) of eyegnat and muscid flies in and around households in a trachoma endemic region in the Brazilian Amazon, and (ii) to evaluate fly density and anthroponotic features as significant risk factors of childhood trachoma. ARTIGO ARTICLE 1682 Cad. Saúde Pública, Rio de Janeiro, 23(7):1682-1688, jul, 2007 FLIES AND TRACHOMA IN LATIN AMERICA 1683 Cad. Saúde Pública, Rio de Janeiro, 23(7):1682-1688, jul, 2007 Materials and methods