Multiple granulomatous lesions in the mesenteric lymph nodes were observed in an 11-month-old cross-bred calf. The appearance of the lesions was caseous and, upon sectioning, it crackled due to the mineralization of the lesions. Veterinary inspectors submitted samples to SESC to confirm a macroscopic diagnosis of bovine tuberculosis.

The histopathological study proved the inspectors right: lesions of granulomatous lymphadenitis, compatible with bovine tuberculosis, were observed, and Ziehl Neelsen’s staining made it possible to identify acid-fast bacilli.

In contrast, PCR for the M.tuberculosis complex gave a negative result, indicating that it was what is commonly called a non-tuberculous mycobacterium.

Microbiological culture and subsequent molecular studies allowed to identify Mycobacterium avium subs. avium as the causative agent.

While in other species such as domestic pigs or wild boar it is quite common to see tuberculous compatible lesions caused by M.avium, it is not a common finding in the bovine species. The origin of this mycobacterium could be poultry and the location of the lesions is indicative of a digestive entry. M.avium is considered a non-tuberculous mycobacterium because it does not cause tuberculosis in humans, even though it can cause lesions in immunocompromised humans. We do not know about the immune status of this calf or the dose of M.avium it ingested, but it is a possibility that must be included in the differential diagnosis of  tuberculosis compatible lesions in cattle. (EV)

Lesions granulomatoses compatibles amb tuberculosi als nòduls limfàtics mesentèrics d'una vedella.

Granulomatous lesions compatible with tuberculosis in the mesenteric lymph nodes of a calf.