Isolation and molecular characterization of Mycobacterium bovis causing pulmonary tuberculosis and epistaxis in a Thoroughbred horse

BACKGROUND: Tuberculosis caused by Mycobacterium bovis (M. bovis) is very uncommon in horses worldwide. CASE PRESENTATION: In the current study, an eight-year-old male Thoroughbred in good body condition was admitted to the Equine Clinic at the Onderstepoort Veterinary Academic Hospital in 2005 due to bilateral epistaxis accompanied by coughing. Routine examinations were conducted to determine the cause of the condition. Endoscopic examination revealed the major source of the epistaxis as the trachea, whereas thoracic radiography indicated the presence of a primary pulmonary mass. M. bovis was isolated from a broncho-alveolar lavage (BAL) sample collected. The pulmonary mass reduced in size three months later following an oral administration of enrofloxacin (7.5 mg/kg PO SID). Genetic fingerprinting by spoligotyping identified the M. bovis isolate as spoligotype SB0868 strain. This M. bovis strain type was never described previously in South Africa (SA). This is the first case of M. bovis infection in a horse in SA which has been fully documented including clinical findings, isolation and genetic characterisation of the causative pathogen. CONCLUSIONS: This report indicates that horses may contract and harbour M. bovis despite their lower susceptibility compared to other domestic animals. It also suggests that the infection may be more easily contained and eliminated from the host.