Isolation of an orthopoxvirus from pox-like lesions of a grey seal (Halichoerus grypus)
Osterhaus, A.D.; Broeders, H.W.; Visser, I.K.; Teppema, J.S.; Vedder, E.J.
Veterinary Record 127(4): 91-92
1990
ISSN/ISBN: 0042-4900 PMID: 2169668 Document Number: 354949
An unusually high incidence of cutaneous pox-like lesions were observed in grey seals (5 out of 12) that were admitted to the Pieterburen Seal Rehabilitation and Research Centre during the outbreak of disease caused by phocid distemper virus (PDV). PDV neutralization tests showed that all the seals had been recently infected with PDV. Electron microscopic examination of negatively contrasted suspensions of the lesions revealed the presence of characteristic parapoxvirus particles in all 5 cases. Orthopoxviruses were also found in the lesions from one of three seals. A cytopathic agent was isolated in primary grey seal skin cells from suspensions of the pox-like lesions shown to contain orthopoxvirus particles. This could be passaged at least three times in these skin cells with cell-free culture medium. The infected cultures were shown, by staining, to develop syncytia and inclusion bodies similar to those seen in other orthopoxvirus infections. Viral antigen was detected by indirect immunofluorescence in these cultures. Orthopoxvirus particles were visualised by electron microscopy in disrupted cell pellets of the cell cultures. It is suggested that immunosuppression due to PDV infection may have made the grey seals more susceptible to infection with para- and/or orthopoxviruses.