Repeated bouts of pulmonary tuberculosis in a hunting cat: reinfection or recrudescence?

• Published in: JFMS open reports Vol. 7; no. 1; pp. 2055116921990292 - 2055116921990297
• Main Authors: Albuquerque, Carolina SC, Černá, Petra, Gunn-Moore, Danièlle A
• Format: Journal Article
• Language: English
• Published: Sage UK: London, England SAGE Publications 01.01.2021; Sage Publications Ltd; SAGE Publishing
• Subjects: Case Report; hypercalcaemia; M microti; Mycobacteria; Mycobacterium tuberculosis complex; Pneumonia; pyogranulomatous; Tuberculosis; M microti; Mycobacterium tuberculosis complex; Mycobacteria; pyogranulomatous; tuberculosis; hypercalcaemia; Mycobacteriumtuberculosis complex
• ISSN: 2055-1169; 2055-1169
• DOI: 10.1177/2055116921990292

Case summary A 7-year-old neutered male Siamese cat was referred for investigation of weight loss and hypercalcaemia (3.3 mmol/l; reference interval 2–3 mmol/l). Haematology, serum biochemistry, thoracic imaging, bronchoalveolar lavage (BAL), Ziehl–Neelsen staining of the BAL fluid and interferon gamma release assay (IGRA) were compatible with pneumonia caused by the less pathogenic member of the Mycobacterium tuberculosis complex, that is, M microti (the ‘vole bacillus’), which is common in cats in the UK. Treatment with azithromycin, rifampicin and marbofloxacin was given for 2 months, followed by 4 months of azithromycin and marbofloxacin. Treatment recommendations for tuberculous pneumonia have since changed. The cat remained asymptomatic for 1 year but went on to develop M microti pneumonia on five other occasions, and was treated for 6–12 months on each occasion. The patient’s clinical signs, hypercalcaemia and radiographic/CT pulmonary pathology always resolved completely, and the IGRA became negative, before antimycobacterial treatment was stopped. This suggests cure followed by reinfection owing to avid hunting behaviour. Alternatively, this could represent recrudescence of dormant disease. This case has previously been included in a study that described a series of cases of feline tuberculosis. Relevance and novel informationThis case shows that M microti infection in cats can present as recurrent episodes of pneumonia, even after prolonged treatment courses.