Hydrocephalus and hearing loss associated with chronic Brucella ceti infection in stranded bottlenose dolphins Tursiops truncatus.

Brucella ceti has a global distribution and is associated with neurologic disease, systemic infection, and reproductive losses in cetaceans. B. ceti has been associated with perinate mortality and sporadic systemic infections in bottlenose dolphins (BNDs) Tursiops truncatus from strandings both during and outside of unusual mortality events on the southern and eastern coasts of the USA. In 2014-2015, 2 BND from the waters of Texas and Florida stranded on separate occasions, were admitted to rehabilitation facilities, and were later placed under permanent professional care. Both dolphins had subtle, nonspecific signs of abnormal health, protracted neurological signs, and bilateral hearing deficits confirmed via serial auditory evoked potentials testing. Case 1 had hydrocephalus diagnosed with advanced imaging, as well as rising Brucella titers, which provided a strong antemortem indication of neurobrucellosis. B. ceti infection was confirmed on postmortem examination in both cases via Brucella PCR on cerebellum (Case 1) or cerebrospinal fluid (Case 2). Pathologic findings included severe hydrocephalus, lymphocytic meningitis and ependymitis, and vestibulocochlear neuritis in both cases. Case 1 also had loss of sensory cells in the inner ear. To our knowledge, these cases represent the first report of Brucella-associated hearing loss and vestibulocochlear neuritis in cetaceans, neurobrucellosis diagnosed in stranded BND admitted to rehabilitation and placed under permanent professional care, and application of advanced imaging to achieve antemortem diagnosis of hydrocephalus in a stranded cetacean. These cases highlight chronic neurobrucellosis as an important differential for stranded dolphins with abnormal behavior or hearing deficits.