Mycobacterial infections are rare in equines. Mycobacterium bovis (M. bovis) is an important zoonotic pathogen causing disease in a wide range of animal species. Infection with M. bovis has not been documented previously in the donkey.
Materials and Methods
A 29-year-old donkey gelding presented with depression, pyrexia, tachycardia, tachypnoea and generalised wheezes and crackles on thoracic auscultation. Haematologic examination identified neutrophilic leukocytosis. Response to treatment with antimicrobials and non-steroidal anti-inflammatories was poor and the donkey was euthanased.
On gross postmortem examination the lungs were diffusely consolidated with an irregular nodular appearance of the surface and multiple coalescing, firm, pale masses diffusely distributed throughout the parenchyma. Multiple, variably sized, firm, pale nodular masses were also identified within the mediastinum, epicardium, omentum, kidneys, liver, spleen and diaphragm. Histopathological examination of lung showed prominent interstitial fibrosis and diffuse granulomatous inflammation in which acidfast bacilli were occasionally identified. The additional nodular masses represented foci of chronic granulomatous inflammation. Culture of lung yielded a heavy growth of mycobacteria confirmed to be M. bovis by molecular techniques (GenoType MTBC).
Although rare in equines, disease caused by M. bovis should be considered as a possible differential diagnosis in donkeys presenting with signs of respiratory disease and respiratory or generalised granulomatous inflammation.