The first patient was a four-year-old neutered male Savannah cat from Inverness, Scotland, who was presented to his general practice veterinarian with an intermittent cough and mild weight loss lasting three weeks. The cat was strictly indoor-only and had been fed a commercially available raw meat-based diet containing poultry and supplemental beef offal. Initial treatment with the anti-inflammatory drug meloxicam produced no response, and over the following two weeks the cough became more persistent while the cat grew increasingly lethargic with a reduced appetite.

Thoracic radiographs revealed a marked broncho-interstitial lung pattern, and a blind bronchoalveolar lavage performed under anaesthesia showed moderate neutrophilic inflammation but was negative on routine bacterial culture. An empirical course of the antibiotic marbofloxacin also failed to help. By the time the cat was referred to a specialist institution, he had lost 30 percent of his body weight. A computed tomography scan showed severe, diffuse nodular to confluent soft tissue lesions affecting all lung lobes, together with enlarged mediastinal lymph nodes. Fine-needle aspirates of consolidated lung tissue revealed severe pyogranulomatous inflammation, and Ziehl-Neelsen staining identified small numbers of acid-fast bacilli with the slender, curved morphology typical of mycobacteria. Culture subsequently confirmed Mycobacterium caprae.

Treatment began with a triple antibiotic protocol comprising pradofloxacin at 5 mg/kg, rifampicin at 10 mg/kg and azithromycin at 15 mg/kg, each given orally once daily in liquid formulations. An oesophagostomy tube was placed to help the owners administer the prolonged medication with minimal stress. The cat was hospitalised in isolation for eight days with strict infection control precautions, including personal protective equipment for staff. Public health officials were notified once the diagnosis was confirmed, but no further testing of in-contact people was deemed necessary. Clinically, the cat improved rapidly, gaining weight within a month and coughing far less frequently. Although repeat radiographs at three-monthly intervals showed only mild improvement, treatment was stopped after eleven months when lung changes had remained static for more than two months. The cat remains clinically normal a year after therapy ended.

The second patient was a three-year-old neutered female British Shorthair from Hampshire, England, who was fed the same raw meat-based diet product and presented with a one-month history of cough, weight loss and fever. Radiographs revealed a cavitating mass in the caudal left lung field, a large nodule in the left cranial lung and multifocal areas of dense consolidation throughout the remaining lung fields. Cytology of a bronchoalveolar lavage sample showed marked neutrophilic and macrophagic inflammation with epithelioid macrophages containing non-staining ghost bacilli, and Ziehl-Neelsen staining again revealed intracellular acid-fast organisms. Polymerase chain reaction testing at a mycobacterial reference laboratory detected DNA of the Mycobacterium tuberculosis complex, and sequencing confirmed M. caprae.

The same triple antibiotic regimen was prescribed, again using liquid formulations to support long-term daily compliance. The cat improved rapidly, gaining weight within a month, with coughing notably reduced by four months of therapy. Radiographs after five months showed significant improvement without complete normalisation, and after a further three months the findings were unchanged. Given the patient was clinically well and had completed nine months of treatment, therapy was discontinued. She remains clinically normal ten months after cessation.

The clinical significance of these cases extends beyond the rarity of the pathogen. In the United Kingdom, feline infections with the M. tuberculosis complex are usually caused by Mycobacterium bovis or Mycobacterium microti, and M. caprae has only recently been identified in domestic cats, previously documented in detail in a single post-mortem case. The treatment protocol used in both cats was adapted from human tuberculosis guidelines and consists of rifampicin, a fluoroquinolone and a macrolide continued for at least three months and for two months beyond resolution of clinical signs. Earlier retrospective work found that only 42 percent of treated cats achieved complete remission, often despite inappropriate therapy, whereas the updated multidrug approach has produced remission rates of approximately 80 percent.

Notably, neither cat achieved radiographic resolution despite extended therapy, yet both remained free of relapse. The authors draw an analogy with post-tuberculosis lung disease in humans, an increasingly recognised spectrum of structural and functional pulmonary abnormalities that persists after successful anti-mycobacterial therapy in 18 to 80 percent of treated patients. They suggest that stable radiographic changes could serve as a reasonable therapeutic endpoint in feline mycobacterial infections where initial lung damage is too severe to be expected to normalise.

The report also underscores the practical demands of treatment. Both cats required prolonged daily multidrug therapy with frequent follow-up visits, demanding substantial financial and emotional investment from their owners alongside excellent patient compliance. The authors caution that where such commitment is not feasible, euthanasia should be considered for severely affected animals, both for welfare reasons and to reduce the risk of antimicrobial resistance developing from inconsistent dosing. They further note that empirical treatment choices early in the diagnostic process, such as anti-inflammatory drugs, can complicate or worsen the clinical course and should be weighed carefully with owners.

Zoonotic considerations shaped the management of both cases. Transmission of M. bovis from cats to humans has been documented previously, although the risk is considered very low, and M. caprae transmission to humans has only been identified in proximity to infected goats, its reservoir host, never from cats. Because no in-contact humans had risk factors for zoonotic transmission, treatment of both cats was judged reasonable. The authors hope that raising awareness of this first reported successful treatment of M. caprae infection in UK domestic cats will aid patient management while mitigating zoonotic risks, and they highlight the oesophagostomy tube used in the first case as a practical aid that reduces stress and supports the owner-caregiver relationship throughout months of therapy.

Subject of Research: Successful treatment of Mycobacterium caprae tuberculosis infection in two domestic cats in the United Kingdom

Article Title: Successful Treatment of Mycobacterium caprae Infection in Two UK Cats

Article References: Clark, E., Gunn‐Moore, D., & O'Halloran, C. (2026). Successful Treatment of Mycobacterium caprae Infection in Two UK Cats. Veterinary Medicine and Science, 12(5), Article e71180. https://doi.org/10.1002/vms3.71180

Image Credits: AI Generated

DOI: 10.1002/vms3.71180

Keywords: Mycobacterium caprae, feline tuberculosis, zoonotic disease, veterinary medicine, triple antibiotic therapy, rifampicin, pradofloxacin, azithromycin, raw meat-based diet, post-tuberculosis lung disease, Mycobacterium tuberculosis complex, UK cats