Systemic Mycobacterium celatum infection in a female domestic ferret

Mycobacterium celatum 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 Mycobacterium spp., with 100% DNA sequence similarity to M. celatum. M. celatum 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 M. celatum has been reported elsewhere in ferrets more commonly than in other animals, M. celatum has not been reported previously in any animal species in North America, to our knowledge. M. celatum should be included as a potential pathogen in systemic mycobacterial infections, especially in ferrets.