Looking Beyond Leishmania infantum: Serological and Molecular Investigation of Leishmania spp. in Domestic Dogs and Cats from a Visceral Leishmaniasis-Endemic Area in Northeastern Brazil

Abstract Purpose The urbanization of zoonotic leishmaniasis and the potential overlap of transmission cycles involving different Leishmania species, vertebrate hosts, and phlebotomine sand fly vectors represent a public health challenge in Latin America. This study aimed to investigate the serological and molecular occurrence of Leishmania spp. in dogs and cats from São Luís, Maranhão, northeastern Brazil. Methods Blood samples from 330 dogs and 21 cats were analyzed by indirect immunofluorescence antibody test (IFAT) using Leishmania infantum and Leishmania amazonensis antigens and by ITS1 Polymerase Chain Reaction–Restriction Fragment Length Polymorphism (ITS1 PCR–RFLP). Results In dogs, seroreactivity against L. amazonensis and L. infantum antigens was detected in 37.9% and 23.0%, respectively, and Leishmania DNA in 58/330 (17.6%). Of nine canine samples successfully characterized by PCR–RFLP, eight showed profiles compatible with L. infantum and one a mixed profile suggestive of both species. In cats, seroreactivity against L. amazonensis and L. infantum antigens was detected in 28.6% and 14.3%, respectively, and L. infantum DNA was identified in two animals. Univariable analysis showed associations between seroreactivity to L. infantum antigen and age, sex, and clinical signs, whereas seroreactivity to L. amazonensis antigen was associated with age, sex, street access, and the reported presence of wild animals around the household. Conclusion The higher seroreactivity to L. amazonensis antigen should be interpreted cautiously because of potential serological cross-reactivity and limited species-level molecular characterization. Together, the findings raise the possibility that Leishmania occurrence in domestic animals in this endemic area may not be restricted to L. infantum , warranting further species-specific investigation.