Case report links canine TB to reverse zoonosis in household

A newly published case report in Frontiers in Veterinary Science details a rare but consequential diagnosis: systemic Mycobacterium tuberculosis infection in a domestic dog, with investigators inferring reverse zoonotic transmission from an infected pet parent and possible onward exposure to another person in the household. The patient, a 4-year-old male American Staffordshire terrier, ultimately underwent euthanasia after progressive multisystem disease, and the report frames the case as a One Health alert for clinicians, pathologists, and public health teams. (frontiersin.org)

The case stands out because canine tuberculosis caused by M. tuberculosis is considered rare and likely underdiagnosed. That rarity can make it easy to overlook in companion-animal practice, especially when signs are nonspecific and overlap with more common inflammatory, respiratory, gastrointestinal, or neoplastic conditions. Earlier reports have already shown that dogs can acquire M. tuberculosis from humans, and a separate case study has highlighted occupational risk to veterinary personnel after necropsy of an infected dog. (frontiersin.org)

In this case, the dog presented with lethargy, acute vomiting, anorexia, weight loss, generalized muscle atrophy, ataxia, and a history of chronic cough, orthopedic disease, and dermatopathy treated with corticosteroids. Clinical evaluation identified hypercalcaemia, oxaluria, and proteinuria. Cytology raised suspicion for mycobacterial disease after granulomatous inflammation and negatively staining bacilli were observed. Necropsy and histopathology later documented disseminated granulomatous hepatitis, nephritis, prostatitis, splenitis, and pneumonia with caseous necrosis and mineralization, and Ziehl-Neelsen staining confirmed acid-fast bacilli in lesions. (frontiersin.org)

The microbiology workup adds weight to the report. According to the authors, PCR/RFLP and core genome multilocus sequence typing identified Mycobacterium tuberculosis complex, while whole-genome sequencing characterized the isolate as a drug-susceptible M. tuberculosis lineage 4.1.2.1, also known as Haarlem. Their epidemiologic investigation supported transmission from a human household contact to the dog, with possible subsequent exposure of a cohabiting person who developed latent infection. That sequence makes the paper notable not just as a pathology case, but as a cross-species surveillance event. (frontiersin.org)

Broader veterinary literature supports the authors’ concern that these cases can have implications beyond the index patient. Prior published reports describe human-to-dog transmission as an established, if uncommon, pathway, and a recent review case from Croatia noted that most documented canine TB cases still appear to originate from humans rather than the reverse. Frontiers’ broader editorial framing for mycobacterial research in 2026 also emphasizes that diagnostic errors and fragmented coordination across human and animal health systems can weaken zoonotic risk management. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary teams, the practical takeaway is that TB belongs on the differential list when a dog presents with systemic granulomatous disease, especially if hypercalcaemia is present and there’s any history of chronic respiratory signs, corticosteroid exposure, or household TB risk. The report suggests hypercalcaemia may have underappreciated diagnostic value in this context, which could help clinicians connect a nonspecific biochemical abnormality to a higher-consequence infectious disease workup. It also underscores the importance of asking about human health exposures in the home, coordinating promptly with public health authorities when TB is suspected, and protecting staff during sampling, hospitalization, and necropsy. (frontiersin.org)

The case may also matter to specialty and referral practices, where unusual inflammatory presentations are more likely to surface. Because confirmation required pathology, acid-fast staining, molecular typing, and genome sequencing, the report highlights the value of referral networks and laboratory partnerships in diagnosing rare zoonotic infections. For practices serving immunocompromised clients, multi-pet households, or rescue and imported-dog populations, the threshold for considering mycobacterial disease may need to be lower than many clinicians assume. That last point is partly an inference from the literature on imported and household-associated canine TB, rather than a direct recommendation from this paper alone. (frontiersin.org)

What to watch: The next question is whether this case changes clinical behavior: watch for follow-on commentary about screening protocols, exposure-history intake, necropsy biosafety, and whether hypercalcaemia gains traction as a useful warning sign in future canine TB case recognition and reporting. (frontiersin.org)