Systemic <i>Mycobacterium celatum</i> infection in a female domestic ferret

<i>Mycobacterium celatum</i> is a slow-growing, non-tuberculous mycobacterium with occasional branching morphology that has been reported mainly in immunocompromised human patients and rarely in other animal species. A 5-y-old female ferret was presented to a veterinary clinic with a history of anorexia and lethargy; peripheral lymphadenopathy, splenomegaly, and pneumonia were detected. Despite treatment, progressive deterioration of the ferret's health led to euthanasia of the animal. Autopsy revealed numerous small 1-4-mm white nodules in the lung, spleen, and kidneys. Histologically, the kidney and lung nodules were pyogranulomas containing slender, elongate acid-fast bacilli with occasional branching. Bacterial culture was negative after 5 d of aerobic incubation. A PCR assay of kidney tissue was positive for <i>Mycobacterium</i> spp., with 100% DNA sequence similarity to <i>M. celatum. M. celatum</i> can cause systemic infection in humans and animals resembling tuberculoid mycobacterial infection. The diagnosis can be challenging due to cross-reactivity with tuberculosis-specific molecular assays and slow growth on bacterial culture. Although <i>M. celatum</i> has been reported elsewhere in ferrets more commonly than in other animals, <i>M. celatum</i> has not been reported previously in any animal species in North America, to our knowledge. <i>M. celatum</i> should be included as a potential pathogen in systemic mycobacterial infections, especially in ferrets.