Leishmania (Viannia) infection in a horse in the state of Goiás, Brazil

This research reports the clinical, histological, immunohistochemical, and molecular findings of a case of leishmaniasis by Leishmania (Viannia) in an equid in the state of Goiás, Brazil. Nodular lesions, sometimes crusty or ulcerated, were observed on the auricular pavilion, neck, and limbs of a four-year-old adult female Quarter Horse. Histomorphological findings indicated granulomatous dermatitis, revealing parasitic structures within macrophages, exhibiting an ovoid to slightly elongated morphology, measuring 2-5 µm, with a rounded nucleus and rod-shaped kinetoplast. Immunohistochemical examination showed positive staining of amastigotes of Leishmania spp. The Polymerase Chain Reaction (PCR) technique, followed by sequencing and BLASTn analysis, enabled the comparison of the percent similarity between the obtained sequences and those deposited in GenBank, which revealed a 100% of identity with sequences of the subgenus Viannia and 97.27% identity with sequences of Leishmania (Viannia) braziliensis deposited in the database. The importance of including leishmaniasis in the differential diagnosis of cutaneous nodular diseases in equids is emphasized, as well as the need for studies to elucidate the importance of these animals in the biological cycle of leishmaniasis.