Socio-economic and environmental factors associated with the occurrence of canine infection by Leishmania infantum in Teresina, Brazil

Abstract

American visceral leishmaniasis (AVL) is a zoonosis caused by protozoan parasites of the genus Leishmania. In Brazil, the disease is caused by Leishmania infantum and the main vector is the phlebotomine sandfly Lutzomyia longipalpis, found both in natural ecotopes and in the rural and urban environments, being very well adapted to the peridomestic environment. The domestic dog has been incriminated as the main reservoir of the parasite in the urban environment, but the control measures based on culling seropositive dogs have not shown to be effective to contain the spread of the disease throughout the country. Many studies evaluated risk factors for human visceral leishmaniasis but few focused on the socioeconomic and environmental factors associated with infection among dogs. Knowledge of these factors might help identify the conditions that contribute to the maintenance of transmission cycles in the urban environment and identify new targets for intervention. The objective of this study was to assess the association between socioeconomic and environmental factors and the occurrence of canine leishmaniasis at Teresina city, Brazil. This cross-sectional study was developed in ten districts of Teresina, involving 532 houses and 810 dogs. Peripheral blood samples were collected by vein punction using vacutainer tubes without anticoagulant for performing serological test (indirect immunofluorescence - IFI). Serum samples with IFI titers ≥1: 80 were considered positive. Owners of the selected dwellings were interviewed using a semi-structured questionnaire addressing socioeconomic and environment aspects. The association between variables and seropositivity was assessed through multilevel logistic regression models. Global seropositivity was 39%. There was no statistically significant difference between seropositivity and age and sex of animals, literacy of the household head, presence of other domestic animals or with household characteristic like water supply, inadequate sewage disposal system, type of floor and roof. Mixed-breed dogs and those living for a long time in houses with absence of masonry walls and presence of a kennel showed higher odds of seropositivity. These results suggest that some peridomestic characteristics, especially the absence of barriers that allow dogs to have free access to the street, in association with the presence of a kennel, might contribute to maintaining the infection cycle in urban areas. Intervention measures oriented to the management of the peridomestic environment and responsible dog possession could be useful tools for reducing disease burden in endemic area.

Keywords: Dogs; Epidemiology; Leishmaniasis; Prevalence; Socio-environmental variables.