Autochthonous canine cutaneous leishmaniasis caused by Leishmania (Mundinia) martiniquensis in Thailand: First evidence with successful intralesional amphotericin B treatment and a review of animal infections worldwide.

Autochthonous human leishmaniasis caused by Leishmania (Mundinia) martiniquensis has been increasingly reported in Northern Thailand. However, the potential animal reservoirs for this parasite remain unidentified. Herein, we report the first documented case of canine cutaneous leishmaniasis caused by L. martiniquensis in a dog from Chiang Mai Province. The patient presented with a firm, non-ulcerative nodule (0.3 × 0.4 cm) on the concave surface of the right ear pinna. Fine-needle aspiration cytology revealed protozoan amastigotes, suggestive of Leishmania infection. The parasite was successfully isolated and cultivated in Grace's insect medium, supplemented with 30% fetal bovine serum. Molecular confirmation was performed using nested polymerase chain reaction (nPCR), real-time quantitative PCR (qPCR), sequencing, and phylogenetic analysis of the internal transcribed spacer 1 region, which classified the isolate as Leishmania martiniquensis. Comprehensive clinical evaluations, including complete blood count, serum biochemistry, and abdominal imaging (radiography and ultrasonography), revealed no evidence of systemic involvement consistent with visceral leishmaniasis. However, persistent polycythemia and mild protein alterations were observed during follow-up. Successful clinical resolution of the cutaneous lesion was achieved after four consecutive weekly intralesional amphotericin B treatments. This report demonstrates that dogs are vulnerable to cutaneous L. martiniquensis infections. A comprehensive review of clinical manifestations of L. martiniquensis infection in animals worldwide is presented, emphasizing the need for further studies on animal infection, vector transmission, and epidemiology within a One Health framework.