Abstract

Two live-stranded cetaceans with similar final diagnoses entered rehabilitation at SeaWorld in San Diego in 2006. The first, a young male Northern Right Whale Dolphin (Lissodelphis borealis), stranded in late May and exhibited no specific hematologic abnormalities. The clinical condition waxed and waned but overall was suggestive of neurologic deficiencies. This animal died spontaneously after two weeks of care. The second animal was an adult female Short-beaked common dolphin (Delphinus delphis) that stranded in December 2006. This animal demonstrated similar non-specific but progressive neurologic deficits and was euthanized after one week of medical care.

Magnetic resonance imaging (MRI) was performed on both animals. Both animals demonstrated a moderate to severe hydrocephalus characterized by dilation of the ventricular system. No focal intracranial abscess, infarct or mass lesions were noted in either animal. Histologic examination of brain tissue revealed a chronic, non-suppurative meningoencephalitis in both animals. In both dolphins the lesions were associated with the isolation of a Brucella sp. from the brain. Both animals had negative titers for dolphin and porpoise morbillivirus. Mild vaginitis and excess vaginal mucous were identified in the common dolphin. Brucella sp. was also isolated from this material. This report provides the first description of an association between Brucella sp. infection and meningoencephalitis induced hydrocephalus changes in a cetacean species.

Cetacean brucellosis has been associated with meningoencephalitis in a variety of species and has been associated with abortions in bottlenose dolphins. Hydrocephalus with very similar histologic findings has been reported in a bottlenose dolphin with severe intervertebral arthritis. These cases suggest a possible larger role for this bacterium in morbidity and mortality of wild cetaceans.