Factors associated with Leishmania infantum infection in dogs from urban areas endemic for visceral leishmaniasis in Brazil

There are gaps in the knowledge of the factors associated with canine visceral leishmaniasis (CVL). Moreover, there is a need for studies conducted with appropriate sample selection and with standardized diagnostic methods, to assess the current infection status of animals. This study analyzed factors associated with Leishmania infantum infection in dogs from urban areas endemic for CVL in Brazil. Data from four cities in different regions of the country (Fortaleza, Brasilia, Palmas, and Bauru) were included, encompassing a large and heterogeneous sample group. Dogs were considered infected if they had positive results in parasitological tests (skin lesion culture, histological or immunohistochemical analysis of skin). Data analysis consisted of logistic regression with adjustment for the effect of cities as cluster variables, using generalized estimating equations. The canine positivity for L. infantum was 9.8%. Bauru had the highest percentage (18.7%), followed by Brasilia (8.4%), Fortaleza (7.9%), and Palmas (4%). Male animals were twice as likely to be infected as females (Confidence Interval (CI): 1.5-2.8). Dogs living outdoors were 1.5 times more likely to be positive (CI: 1.4-1.6). Dogs living in households rearing chickens were 40% less likely to be infected (CI: 0.5-0.8). A significant multiplicative interaction indicated that a protective association between purebred and CVL was stronger among dogs older than seven years. These findings provide evidence for the role of individual and environmental factors on L. infantum infection in dogs from endemic urban areas. They may be used for identifying groups of animals at higher risk for delivering control interventions.