Granulomatous pneumonia caused by Mycobacterium genavense in a dwarf rabbit (Oryctolagus cuniculus)

A juvenile dwarf rabbit (Oryctolagus cuniculus) with clinical signs of dyspnea and suspected ascites was submitted for necropsy. The main macroscopic findings were a watery red pleural effusion and some whitish striated foci in the lungs. In addition, there were multifocal scars in the cortex of the kidneys. The histologic examination of the lungs showed a severe granulomatous pneumonia with detection of acid-fast bacilli, in the kidneys, an interstitial chronic lymphoplasmacellular nephritis with interstitial fibrosis, and in the brain, a multifocal granulomatous and partly necrotizing encephalitis with detection of spores, suggestive of encephalitozoonosis. In the lungs, Mycobacterium genavense was verified by polymerase chain reaction and 16S ribosomal RNA gene sequencing. To our knowledge, this is the first report of an M. genavense infection in a rabbit, with the lungs being the only affected organ. Therefore, an aerogen infection seems to be the most contemplable way of infection.