Seven juveniles from a group of wild-caught dusky smooth-hounds developed inappetence and multifocal irregular skin lesions while in quarantine. All of these individuals died over a 3-month time period (December 2006–March 2007) despite medical and supportive therapy. All sharks had evidence of ulcerative dermatitis with intralesional ciliated protozoans and septicemia on histopathology. One of these juveniles had hypertrophy and hyperplasia of the oral mucosal epithelium associated with the formation of large intranuclear basophilic inclusions. A second shark had diffuse marked subacute branchitis with intraepithelial intranuclear inclusions. Electron microscopy performed on gill extracted from paraffin block revealed that the intranuclear inclusions contained hexagonal viral particles 60–65 nm in diameter consistent with an adenovirus.
Postmortem tissues from five adult sharks that expired between May and August 2007 were submitted for viral culture and isolation. A replicating agent isolated from the tissues induced cytopathic effect on primary shark embryo cells and was transferable in cell culture. No viral particles were observed in cell culture supernatant samples submitted for electron microscopy. A sample of the cell culture monolayer was submitted for electron microscopy. In addition, a sample of the cell extract and supernatant was submitted for PCR using an adenovirus primer set. Results of these ancillary tests are still pending.
Adenovirus infections are rare in fish. Documented cases have been reported in Atlantic cod (Gadus morhua),3 dab (Limanda limanda),1 and white sturgeon (Acipenser transmontanus).2,4 To the authors’ knowledge, this is the first confirmed report of an adenovirus infection in an elasmobranch.
1. Bloch, B., S. Mellergaard, and E. Neilsen. 1986. Adenovirus-like particles associated with epithelial hyperplasias in dab, Limanda limanda (L.). J. Fish Dis. 9: 281–285.
2. Hedrick, R.P., J. Speas, M.L. Kent, and T. McDowell. 1985. Adenovirus-like particles associated with a disease of cultured white sturgeon, Acipenser transmontanus. Can. J. Fish. Aquatic Sci. 42: 1321–1325.
3. Jensen, N.J., and B. Bloch. 1980. Adenovirus-like particles associated with epidermal hyperplasia in cod (Gadus morhua). Nord. Veterinaermed. 32: 173–175.
4. Kovács, G.M., S.E. LaPatra, J.C. D′Halluin, and M. Benko. 2003. Phylogenetic analysis of the hexon and protease genes of a fish adenovirus isolated from white sturgeon (Acipenser transmontanus) supports the proposal for a new adenovirus genus. Virus Res. 98: 27–34.