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Six young cats, living exclusively indoors in five different households across England were presented to separate veterinarians across the UK with various clinical signs due to tuberculous disease.
Methods: Investigations into the pyogranulomatous lesions, lymphadenopathy and/or pulmonary disease of these cases consistently identified infection with Mycobacterium bovis. Infection was confirmed by PCR where possible or was indicated with a positive interferon gamma release assay (IGRA) where material for PCR was unavailable. In-contact, cohabiting cats were screened by IGRA and follow-up testing undertaken/advised where these were positive. A lifestyle investigation was undertaken to identify the source of infection.
Results: Six clinically sick cats and seven in-contacts have been identified with evidence of M. bovis infection. Five clinical cases were either too sick to treat or deteriorated despite therapy, giving a mortality rate of 83%. Lifestyle investigations revealed the common factors between clusters to be; that affected cats had mycobacterial infections speciated to M. bovis, were exclusively indoor cats and were fed a commercially available raw food product produced by a single manufacturer. The Food Standards Agency, Animal and Plant Health Agency, Public Health England and the food manufacturer concerned have been notified/informed.
Other possible sources of exposure for these cats to M. bovis were explored and were excluded; including wildlife contact, access to raw milk, the presence of rodent populations inside the buildings in which the cats lived, and exposure to known infectious humans.
Conclusions and relevance: Upon investigations, our results provide compelling, if circumstantial, evidence of an association between the commercial raw diet of these cats and their M. bovis infections.