Fatal lung tuberculosis in a young cat caused by Mycobacterium orygis

Abstract

Feline tuberculosis, involving members of the Mycobacterium tuberculosis complex (MTBC), presents ongoing diagnostic and public health challenges. Mycobacterium orygis, an emerging and genetically distinct MTBC member, is increasingly recognized for its wide host range, including humans, domestic livestock, and wildlife, particularly in South Asia. We report the first documented case of fatal pulmonary tuberculosis caused by M. orygis in a domestic cat. A 5-month-old stray domestic shorthair cat in India presented in profound shock with severe, rapidly progressive respiratory distress. Thoracic radiography showed a diffuse bronchointerstitial pattern. Diagnostic workup of bronchoalveolar lavage fluid showed abundant acid-fast bacilli on Ziehl-Neelsen staining. Definitive diagnosis was achieved through advanced molecular methods: MTBC-specific real-time PCR followed by sequencing of the ETR-D spacer and gyrB gene, which identified the species as M. orygis. The patient succumbed to the fulminant disease within 24 hours of presentation. This finding establishes the domestic cat as a previously unrecognized host for M. orygis and highlights the pathogen's capacity to cause severe pulmonary infection. Given the documented circulation of M. orygis among humans, livestock, and wildlife in India, this case underscores a critical and often-overlooked zoonotic risk, emphasizing the necessity of integrated veterinary and public health surveillance and rapid molecular diagnostics for species-level identification of MTBC infections.