Coinfection by Mycobacterium marinum and Mycolicibacterium fortuitum in a captive adult diamondback water snake causing disseminated mycobacteriosis with acute cutaneous ulceration.

An adult male captive diamondback water snake (Nerodia rhombifer) was found dead after a 1-d history of lethargy and cutaneous ulcers. The snake had eaten 2 sunfish (Mola spp.) 5 d before death. Gross examination revealed white-to-tan nodules in the lung and liver and segmental intestinal impactions with digested fish. Histopathology confirmed disseminated granulomas with numerous intrahistiocytic acid-fast bacteria in the skin, skeletal muscle, lung, liver, and intestines. Mycobacterium marinum and Mycolicibacterium fortuitum were identified by culture of the hepatic granuloma, followed by PCR and rpoB gene sequencing. To our knowledge, this is the first description of M. marinum and M. fortuitum coinfection in this species. Although M. fortuitum has been isolated from reptiles, lesions associated with its presence in tissues have not been described previously. Interestingly, the mineralization within granulomas that we observed in our case is not reported in mycobacterial infection in reptiles, whereas this finding is common in mammals.

Mandibular osteosarcoma in a nutria (Myocastor coypus).

A four-year-old neutered male nutria (Myocastor coypus) was presented for a one-day history of lethargy and anorexia. A right-sided facial swelling and loose right mandibular fourth molar that exuded caseous exudate from the root were noted; however, the animal continued to decline despite removal of the affected tooth and antibiotic and anti-inflammatory therapy. Radiographs showed a lytic proliferative bony lesion on the right mandible that appeared to expand in size over the course of a week. Due to its declining clinical condition and poor response to therapy, the animal was euthanized. Necropsy revealed an invasive bony neoplasm of the right mandible, histologically consistent with an osteosarcoma, that was invading the mandible and dental arcade, likely contributing to tooth root infection and osteomyelitis. Endocardiosis of the tricuspid valve was incidentally found as well with early cardiac remodeling of the right ventricle. This is the first report of an osteosarcoma and endocardiosis in a nutria.