Molecular analysis of parapoxvirus from a spotted seal Phoca largha in Japan.

A spotted seal Phoca largha with nodular and scab lesions on the whole body was brought to an aquarium in Nagoya, Japan. We extracted DNA from the lesions and used the polymerase chain reaction (PCR) method for detecting orthopoxvirus and parapoxvirus DNA. Parapoxvirus but not orthopoxvirus DNA was detected. The partial nucleotide sequence of the envelope gene was determined from the PCR product, and the sequence was seen to be closely related to 2 parapoxvirus strains from spotted seals in Alaska, showing 100% identity at the amino acid level, with one nucleotide substitution. Virus-neutralizing (VN) antibody against canine distemper virus (CDV) was not detected in the serum, indicating that this individual was not infected with CDV or phocine distemper virus (PDV), which both have a high mortality rate for marine mammals. These results suggest that the lesions were caused by infection with pinniped parapoxvirus, and that the viruses spread and are maintained within the habitat range or populations of spotted seals from the Bering Sea to the Japan Sea. This is the first report of molecular analysis of parapoxvirus in marine mammals in Japan.