Hepatic microgranulomas caused by Mycobacterium marinum (MM) in a Horsfield tortoise (Testudo horsfieldii) presenting with a non‐healing limb granuloma

Abstract

A 3‐year‐old, male, entire Horsfield tortoise (Testudo horsfieldii) presented with a non‐healing lesion on the dorsal aspect of the elbow. Fine‐needle aspiration cytology revealed granulomatous inflammation with acid‐fast staining organisms. Due to worsening clinical condition, the animal was euthanased. Postmortem examination included histopathology, Mycobacterium culture and polymerase chain reaction testing. There was gross hepatomegaly and a large, turbid, straw‐coloured, coelomic effusion. Limb granuloma and liver tissue were sent for mycobacterial polymerase chain reaction and culture, and both were positive and confirmed disseminated Mycobacteria marinum. The origin of the infection is not known, but suspected to originate from poor hygiene from the place of purchase and dissemination secondary to the initial limb granuloma. This represents an uncommon presentation and the first reported infection by this mycobacterial agent in the species. It is important to consider mycobacterial disease as a differential in granulomatous infections, given the range of presentations possible in reptile patients.