Morbilliviral epizootic in bottlenose dolphins of the Gulf of Mexico

Morbillivirus infection was diagnosed in 35/67 bottlenose dolphins (Tursiops truncatus) from the Gulf of Mexico that stranded from October 1993 through April 1994 in Alabama, Mississippi, and Texas (USA) during periods of increased dolphin strandings in each of the 3 states. Diagnosis was based on histologic lesions, immunohistochemical demonstration of morbilliviral antigen, and detection of morbilliviral RNA by a reverse transcriptase polymerase chain reaction (RT-PCR) test performed on formalin-fixed, paraffin-embedded tissue (5 dolphins), on histologic lesions and detection of morbilliviral RNA by RT-PCR performed on formalin-fixed, paraffin-embedded tissue (1 dolphin), and on detection of morbilliviral RNA by RT-PCR performed on unfixed lung samples collected from carcasses with advanced postmortem autolysis (29 dolphins). Histologic lesions included proliferative interstitial pneumonia with syncytial cells and eosinophilic intranuclear and intracytoplasmic inclusion bodies, lymphoid depletion and syncytial cells with eosinophilic intranuclear inclusion bodies in lymph nodes, eosinophilic intracytoplasmic inclusion bodies in transitional epithelium of urinary bladder, and a syncytial cell with eosinophilic intranuclear inclusion bodies in epidermis. Concomitant pulmonary aspergillosis was diagnosed histologically in 4 dolphins. This is the 5th reported morbilliviral epizootic of aquatic mammals and the 2nd involving bottlenose dolphins in the United States.