1Armed Forces Institute of Pathology, Washington, DC, USA; 2Walter Reed Army Institute of Research, Washington, DC, USA; 3 New Bolton Center, University of Pennsylvania, Kennett Square, PA, USA; 4Marine Mammal Stranding Center, Brigantine, NJ, USA
Over the last 14 year, morbilliviruses have emerged as causes of epizootics that killed tens of thousands of pinnipeds and cetaceans.1 When stranded marine mammals are brought into facilities for rehabilitation, there is a risk of transmission of morbillivirus to resident marine mammals with potentially catastrophic results. The purpose of this report is to describe the clinicopathologic findings and results of immunohistochemical and reverse transcriptase polymerase chain reaction testing of two seals with morbilliviral dermatitis. In 1998, rehabilitation of a juvenile female hooded seal (Cystophora cristata) and a juvenile male harp seal (Phoca groenlandica) that stranded on the New Jersey coast was attempted. Clinically, both were lethargic, emaciated and had dermatitis. The hooded seal became dyspneic and died 16 days after stranding. The harp seal died 10 days after stranding. Necropsy findings in the hooded seal included emaciation, pneumonia, rhinitis and gastric nematodiasis; those in the harp seal included emaciation and gastrointestinal nematodiasis. Skin lesions in the hooded seal affected the front flippers, the abdominal area and a rear flipper. The gross appearance was not described. The harp seal had areas of alopecia and crusting that affected the dorsal surface of a flipper, cranial and dorsal tail, caudal and dorsal sacrum, and areas just dorsal to two flippers. Similar, highly distinctive histologic skin lesions were present in both animals. There was epidermal and follicular epithelial hyperplasia, hyperkeratosis and necrosis, with many, variably sized and shaped syncytial cells in epidermis, follicular epithelium and sebaceous glands. Eosinophilic intracytoplasmic inclusion bodies were observed in epithelial cells and syncytia. Small numbers of neutrophils and lymphocytes were present in the epidermis and periadnexal dermis. There was marked bacterial and fungal overgrowth on the surface of the hyperkeratotic crust. Morbilliviral antigen was demonstrated in the skin lesions by immunohistochemistry. Phocine distemper virus (PDV) was detected in the skin by RT-PCR and PDV-specific probe using the Southern blot technique.2 The hooded seal also had lymphoid depletion of spleen and lymph nodes and suppurative bronchopneumonia from which Bordetella bronchiseptica was cultured; eosinophilic intracytoplasmic inclusion bodies characteristic of morbilliviral infection were present in bronchiolar epithelium. The harp seal had lymphoid depletion of lymph nodes, but no pneumonia. This is the first report of morbilliviral dermatitis in seals. Harp and hooded seals with alopecia and crusting dermatitis should be considered potentially infected with morbillivirus. Morbillivirus-infected harp seals may not have respiratory disease. Skin biopsy can provide definitive diagnosis of morbilliviral disease in hooded and harp seals.
1. Kennedy, S. 1998. Morbillivirus infections in aquatic mammals. J. Comp. Pathol. 119:201–225.
2. Krafft, A., J. H. Lichy, T. P. Lipscomb, B. A. Klaunberg, S. Kennedy, and J. K. Taubenberger. 1995. Postmortem diagnosis of morbillivirus infection in bottlenose dolphins (Tursiops truncatus) in the Atlantic and Gulf of Mexico epizootics by polymerase chain reaction-based assay. J. Wildl. Dis. 31:410–415.