Antemortem Diagnosis of Hydrocephalus and Hearing Loss Associated with Chronic Brucella Infection in a Stranded Rehabilitated Bottlenose Dolphin (Tursiops truncatus)
A subadult, underweight, female bottlenose dolphin (Tursiops truncatus) stranded near Galveston, Texas. Over the course of nine months of rehabilitation the animal underwent treatment for parasites, gastric ulcers and a lower respiratory tract infection. Hearing was evaluated via auditory evoked potentials (AEP) due to abnormal feeding behaviors, and results demonstrated significant bilateral hearing impairment. The dolphin was deemed non-releasable based on an inability to forage using echolocation and was moved to a zoological park, where additional health evaluation was performed, prior to integration with other Tursiops at the facility. Over the subsequent two months, the animal displayed progressive abnormal behavior including: marked inactivity, decreased mental alertness, prolonged periods of floating in lateral recumbency, head tilt, vision deficits, perceived lack of interaction with dolphins in adjacent pools, and decreased appetite. Ultrasonographic examination identified pleuritis, pneumonia, and lymphadenopathy. Computed tomography revealed left cranioventral lung consolidation and marked hydrocephalus. Magnetic resonance imaging was performed for further evaluation of CNS lesions. Brucella titers (cELISA) evaluated over six weeks were positive and rose slightly. Due to the severity of the hydrocephalus, declining mental status, poor prognosis, and concerns of pathogen transmission, the animal was euthanized. On post-mortem examination, severe hydrocephalus, meningitis, and bilateral degeneration of the vestibulocochlear nerves were diagnosed. Cerebral spinal fluid was positive for Brucella sp. via PCR. To our knowledge, this is the first report of antemortem diagnosis of hydrocephalus and hearing loss in a cetacean caused by Brucella sp. and has important implications for medical management and placement of stranded cetaceans.
The authors thank the veterinary and animal care teams at Brookfield Zoo and the volunteer staff at Texas Marine Mammal Stranding Network for their assistance with this challenging case.
* Presenting author