Occurrence of <i>Leishmania infantum</i> in Horses from Brazilian Amazon

<b><i>Background:</i></b> Visceral leishmaniasis is a zoonosis distributed throughout Brazil and caused by the protozoan Leishmania infantum. The disease manifests in its visceral form, with dogs being the primary reservoir. Manaus is the largest city in the Brazilian Amazon region, and despite its significance, there are only documented cases of cutaneous leishmaniasis in humans. The aim of this study was to assess the occurrence of Leishmania infantum in horses in Manaus, Amazonas, Brazil. <b><i>Materials and Methods:</i></b> A total of 178 horses from 16 different properties within the city were sampled, and the specific molecular diagnosis was based on the L-like cathepsin gene. <b><i>Results:</i></b> Of the 178 horse samples, 82% were positive for L. infantum in the molecular diagnosis based on the L-like cathepsin gene, and of the 16 different properties sampled, only one did not have any positive animals. <b><i>Conclusion:</i></b> The role of horses in the transmission cycle of visceral leishmaniasis remains controversial, but the presence of infected horses before the appearance of human cases suggests that this host group could be considered sentinel, and their monitoring may serve as an early warning for the emergence of leishmaniasis in a given area.