Are opossums a relevant factor associated with asymptomatic Leishmania infection in the outskirts of the largest Brazilian cities?

Abstract

A population survey was conducted to explore the prevalence and factors associated with Leishmania infection in the Fercal region of the Federal District. The Fercal region is a group of neighborhoods in Brasília in which the first cases of visceral leishmaniasis were described. Leishmania infection was established by a positive leishmanin test. Although other tests were performed in the study (an immunochromatographic assay (Kalazar detect(®)) and a molecular assay), only the leishmanin skin test provided sufficient results for the measurement of the disease prevalence. Data on the epidemiological, clinical and environmental characteristics of individuals were collected along with the diagnostic tests. After sampling and enrollment, seven hundred people from 2 to 14 years of age were included in the study. The prevalence of Leishmania infection was 33.28% (95% CI 29.87-36.84). The factors associated with Leishmania infection according to the multivariate analysis were age of more than seven years and the presence of opossums near the home. Age is a known factor associated with Leishmania infection; however, the presence of wild animals, as described, is an understudied factor. The presence of opossums, which are known reservoirs of Leishmania, in peri-urban areas could be the link between the rural and urban occurrence of visceral leishmaniasis in the outskirts of largest Brazilian cities, as suggested by previous studies.

A cross-sectional approach including dog owner characteristics as predictors of visceral leishmaniasis infection in dogs

“…The detection of asymptomatic-infected dogs is important in terms of epidemiological surveillance, especially because autochthonous cases of human VL have been reported in this region. (20,21) Issues related to the detection of infected animals are even more concerning when assessing the seroprevalence of infection based on the combination of results from the TR DPP/ EIE-CVL tests, (31) currently recommended by a disease control program (9.38%; 95% CI: 5.76 to 14.89), which were markedly lower than the estimate obtained by combined methodologies that included molecular diagnosis. The under-detection of cases of asymptomatic canine infection caused by the lack of sensitivity of the methods recommended for routine examination has already been highlighted by other authors as a possible factor associated with the lack of effective CVL control measures currently recommended in Brazil.…”

“…Location of study -Data collection was performed in the XXXI administrative region of the Federal District, named Fercal. This location is endemic for human and canine cases of VL (20,21) (Fig. 1).…”

Improving the reference standard for the diagnosis of canine visceral leishmaniasis: a challenge for current and future tests

“…Although the endemic area where the study was done had produced a small number of HVL cases, human infection seems to be of relevant magnitude. 50 The area has been monitored and targeted with the traditional interventions recommended by the visceral leishmaniasis control program. Moreover, it would be useful to consider that the rapid dispersion of CVL across the continent brings the need of sensitive tests for early detection of such dispersion.…”

Factors associated with human visceral leishmaniasis cases during urban epidemics in Brazil: a systematic review

“…Carranza-Tamayo et al . (2016) demonstrated that VL infection in humans was associated with an age greater than 7 years. Oliveira et al .…”