Distribution and occurrence of Leishmania infantum chagasi causing canine visceral leishmaniasis in an endemic area of Brazil

Abstract

Leishmaniasis exhibits a spatial distribution strongly influenced by multiple factors. Epidemiological studies conducted in locations close to endemic areas are mandatory to monitor disease spread. Porto Nacional, Tocantins State, Brazil, is an endemic area for canine visceral leishmaniasis (CVL) with high transmission rates, yet few studies have examined parasite isolation in dogs. OBJECTIVES: To determine the impact of seropositive dog euthanasia on the incidence of human visceral leishmaniasis (HVL) cases and identify the Leishmania species circulating in dogs with CVL in Porto Nacional from 2010 to 2019. MATERIALS AND METHODS: Seropositive dogs for CVL from Porto Nacional were tested for parasite DNA using polymerase chain reaction (PCR) and immunohistochemistry for species characterization. Data on animals were obtained from the local Center for Zoonosis Control, and HVL notifications (2010–2019) were retrieved from the National Disease Notification System. RESULTS: Leishmania infantum chagasi was the only species detected by PCR in infected dogs. The number of seropositive dogs increased over time, with the highest number in 2019. The most frequent clinical signs were lymphadenomegaly (73%), skin lesions (70%), and hepatomegaly (63%). No positive correlation was found between euthanasia of seropositive dogs and HVL incidence. CONCLUSION: L. infantum chagasi was confirmed in infected dogs, underscoring the need to revise and adapt control strategies to local contexts in order to better assess the role of infected dogs in leishmaniasis endemic areas.