Assessing reservoir host status in leishmaniasis with special reference to the infectiousness of Leishmania (Viannia) braziliensis infections in wild rodents

ABSTRACT Molecular methods have been responsible for a notable increase in the detection of Leishmaniinae infections in wild animals. Determining their infectiousness is of paramount importance in evaluating their epidemiological significance. One of the most efficient ways of determining infectiousness for vector borne diseases is xenodiagnosis with the appropriate vector. However, this is logistically very difficult to accomplish in the field, and an ideal solution is to find a molecular surrogate for xenodiagnosis. In this review we discuss different approaches to the problem by focusing on the infectiousness of Leishmania (Viannia) braziliensis in rodents under laboratory and field conditions. Comparisons with similar studies for other Leishmania species emphasizes that there are pivotal differences in the infectiousness and the importance of asymptomatic infections in different hosts. Potentially the most promising surrogate is the real time quantitative PCR (qPCR). However, its success depends on choosing a tissue that relates to the vector's feeding location and the parasite's tissue tropism. This requires detailed knowledge of the infection of each species in its wild hosts. We conclude that for L. (V.) braziliensis infections in wild rodents the tissue of choice for a molecular xenodiagnostic test, based on the qPCR is blood, providing that a significant number of samples must be examined.

Preliminary evidence that synanthropic flies contribute to the transmission of trachoma- causing Chlamydia trachomatis in Latin America

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 percent (45/187), present in 46.2 percent 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.

Insetos sinantrópicos são importantes vetores mecânicos de Chlamydia trachomatis, causadora de tracoma, contudo, estudos entomológicos não são freqüentes na América Latina. Esse estudo determina a relação entre densidade de dípteros domésticos e tracoma ativo na infância em uma vila na Ilha do Marajó, Estado do Pará, Brasil. Moradores de 78 residências foram examinados para sinais de tracoma e a relativa abundância de potenciais vetores de tracoma (Diptera, Chloropidae e Diptera, Muscidae) foi quantificada junto com medidas adicionais de higiene doméstica associada com a transmissão de C. trachomatis. A prevalência de tracoma ativo na infância foi 24,1 por cento (45/187), presente em 46,3 por cento das residências amostradas com evidência de aglomeração de casos. A prevalência na infância foi positivamente associada com o aumento das densidades de insetos, enquanto medidas indiretas de condições sanitárias (possuir latrina e perceber a importância dos insetos) foram protetoras. Esse estudo indica que C. trachomatis pode ser transmitida por insetos sinantrópicos nessa região da América Latina.