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Infection studies in harbour seal (Phoca vitulina) were conducted with the Snyder-Hill strain of canine distemper virus (CDV) that is virulent for dog and mink. The inoculated seals showed clinical symptoms which were to some degree similar to those observed in CDV infections of sensitive species of carnivores. Viral replication in lymphoid cells was followed by an extended period of immunosuppression. The results did not provide conclusive evidence for viral replication in surface epithelia of seals, and accordingly no spread of the infection to contact seals and mink was demonstrated. The pathogenicity of the infection did not increase upon a second viral passage in seal. The serological data showed that CDV-infected seals mounted an early virus specific antibody response. Overall, the results indicated that the harbour seal was not especially sensitive to CDV infection. The differences in the in vivo biological properties of CDV and PDV add to the distinction between these viruses at the genomic and antigenic levels.

The antigenic relationships between PDV and isolates of morbilliviruses from carnivores suffering from distemper were investigated. Fourteen isolates, originating from terrestrial carnivores and harbour seals from 1985-1991 from Denmark, Norway, Greenland, and the U.S.A. were reacted in IFA and ELISA with monoclonal antibodies (MAbs) directed against four virion proteins (NP, P, F, and H). The MAbs comprised a newly completed panel of 36 anti-PDV MAbs and 39 previously developed anti-CDV MAbs. The antigenic make-up of the isolates separated them into the CDV prototype group and the PDV prototype group, having the antigenic characteristics of the reference vaccine strains of CDV and the Danish PDV isolate, respectively. The minor antigenic variations within the CDV group contrasted markedly to the differences encountered between the CDV and PDV group. The PDV group included isolates made in 1988 from diseased seals of Danish and Norwegian waters and isolates made in 1989 from distemper outbreaks in Danish mink farms. In contrast, the other distemper isolates investigated, including isolates from 1986 from a corresponding Danish mink farm, revealed the antigenic characteristics of CDV. Our results strongly indicate that PDV was recently transmitted from diseased seals to terrestrial carnivores causing distemper epizootics among farmed mink.

Avian influenza viruses of H3N8, H11N4, H7N7, H8N4, and H5N3 infected mink by contact.

Morbillivirus derived from diseased harbour seals (Phoca vitulina) has characteristics of acute virulent canine distemper virus infection in mink. The infection induced a disease resembling the acute systemic and nervous form of canine distemper.

The antigenic relationships between three similar parvoviruses, canine parvovirus type 2 (CPV), feline panleukopenia virus (FPV) and mink enteritis virus (MEV) were investigated. Antisera against all 3 viruses and monoclonal antibodies (mAb) to CPV were prepared and the viruses compared using several serological methods. When conventional sera were used in the hemagglutination-inhibition and agar gel precipitin (AGP) tests there were no differences between the CPV viral isolates studied, but antigenic differences were revealed between the CPV isolates and the FPV or MEV. Of 16 mAb produced against CPV, six reacted only with the CPV. The other 10 mAb reacted with all three parvoviruses. Additionally, an antigenic difference was detected by AGP tests between one FPV isolate and the other FPV and MEV isolates. Including both conventional sera and mAb to CPV in a single AGP test with the CPV, MEV and FPV antigens permitted the comparison of results obtained with the different antibodies. The results reported revealed antigenic differences between CPV and FPV or MEV that were most clearly defined using mAb.

Two recently recognized viruses obtained from a dog with glossitis and from mink with hemorrhagic pneumonia were characterized by electron microscopy. The results of the negative-stained preparations indicated that the viruses were structurally compatible with the calicivirus group.

The base sequences of the coding region of the nucleoprotein (NP) genes of two H 10 influenza A viruses, one avian (virus N) and one mink virus, have been determined by primer extension. When the NP genes and the NP sequences derived from the only open reading frame of the two H 10 viruses were compared with those of other human and avian influenza A viruses, it turned out that the mink virus NP was highly related to that of other avian strains, but differed from that of the human strains. Comparison of the NP genes of the mink and avian strains of European origin suggests a direct lineage between them. Since the NP plays a major role in species specificity, it is assumed that an avian influenza virus has directly invaded the mink population.