Fluctuating hypercalcaemia caused by cavitary Mycobacterium bovis pulmonary infection

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

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 INFORMATION

This case shows that M microti infection in cats can present as recurrent episodes of pneumonia, even after prolonged treatment courses.

Farmer and veterinarian attitudes towards the risk of zoonotic Mycobacterium bovis infection in Northern Ireland

Based on a qualitative social science research methodology using semi-structured interviews, this paper examines the attitudes of farmers and veterinarians in Northern Ireland around the risk of acquiring tuberculosis caused by Mycobacterium bovis from infected cattle and drinking raw milk. This region has traditionally had one of the highest rates of bovine tuberculosis in the United Kingdom and among the highest in Europe. The research finds that the risk is often downplayed and considered so rare that it is no longer a significant public health risk due to the pasteurisation of milk and intensive surveillance on farms through systematic testing and removal of positive animals, as evidenced by the low recorded human incidence. Although the incidence of tuberculosis in humans caused by M bovis is only around 1% of all annual human tuberculosis cases, this paper argues that M bovis may be underestimated as a human pathogen and makes the case for a renewed perspective. Discourses surrounding the disease may need to be re-orientated to remind relevant stakeholders that human infection with M bovis is a hazard that needs to be treated with more caution on the front line of control.