Canine tuberculosis: A review of 18 new and 565 previously reported confirmed cases

Cases of canine tuberculosis, a zoonotic infection of significant public health significance, are typically only sporadically reported in the literature. For this observational study, case details were collated both retrospectively and prospectively for dogs infected with Mycobacterium tuberculosis-complex (MTBC) organisms. A total of 18 previously unreported cases as well as 565 historically reported confirmed cases were reviewed. A variety of diagnostic techniques were used to make a confirmed diagnosis of tuberculosis (culture, interferon-gamma release assay [IGRA], and PCR). The reference standard for diagnosis is culture; however, this was negative or not attempted in some dogs. Where fully speciated, all cases were caused by infection with one of three MTBC organisms: M. tuberculosis, Mycobacterium bovis, or Mycobacterium microti. This study includes the first documented canine infections with M. microti in the UK. All cases were assigned to one of four clinical groups based on the presenting signs: 44.1% were primarily pulmonary, 14.5% were primarily abdominal, and the remainder were disseminated or miscellaneous. The development of adjunctive tests remains necessary to support early treatment decisions pending reporting of culture for MTBC organisms, which can take weeks to months. Definitive treatment, where attempted, was successful in most cases. Of the 13 dogs treated by the authors with triple combination antimicrobial therapy, a good clinical outcome was seen in 12 (92%) of them.