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ABSTRACT. Serological analysis was performed to detect Toxoplasma gondii and Neospora caninum infection in seals in Hokkaido. Serum samples were collected from 322 Kuril harbor seals (Phoca vitulina stejnegeri) at Nosappu, Akkeshi and Erimo, from 46 spotted seals (P. largha) at Nosappu, Erimo, Yagishiri Island, Hamamasu and Syakotan, and from 4 ribbon seals (P. fasciata) and a bearded seal (Erignathus barbatus) Toxoplasma gondii and Neospora caninum, which are apicomplexan protozoa with worldwide distribution, cause neuromuscular disease and abortion through transplacental transmission in warm-blooded hosts [6,37]. T. gondii and N. caninum infections have been reported mainly in terrestrial mammals and birds, although recently they have been found in wild marine mammals, including several species of seals [8]. T. gondii infection is known to be a major cause of encephalitis in sea otters (Enhydra lutris) [4,8]. The ingestion of oocysts in contaminated food or water and the ingestion of infected tissues of intermediate hosts are the two main sources of postnatal T. gondii and N. caninum infection. Felids and dogs are the only known host that can excrete environmentally resistant oocysts of T. gondii and N. caninnum, respectively [6,37]. Miller et al. [20] presented evidence that land-based surface runoff was a significant risk for T. gondii infection in sea otters. It is possible that oocysts of these protozoa wash into the sea in runoff contaminated by excrement of cats and dogs. In Hokkaido, influx of runoff contaminated with substances such as pesticides and organic matters into environmental water has been known, and it is particularly serious in the snowmelt season [29,30]. Cryptosporidium parvum oocysts that are genetically similar to C. parvum infected in cattle have been detected from river in Hokkaido [38]. If the coastal Hokkaido has been contaminated by terrestrial protozoa, marine mammals may have been infected.Around Hokkaido, there are 5 species of seals: The Kuril harbor seal (Phoca vitulina stejnegeri), the spotted seal (P. largha), the ringed seal (P. hispida), the ribbon seal (P. fasciata) and the bearded seal (Erignathus barbatus) [16]. Kuril harbor seals are distributed along the northwestern Pacific coast [17]. These seals haul out year round on rocky reefs near land and have a strong fidelity to their particular hauling-out site [28]. The four other species migrate in winter and spring, drifting south to Hokkaido with the packed ice [16]. The four species are distributed in the Sea of Japan and the Sea of Okhotsk mainly, although some spotted seals can be found along the Pacific coast all the year round [15,23,24]. Miller et al. [21] reported antibodies against N. caninum from an encephalitic Pacific harbor seal (P. v. richardsi) that had demonstrable T. gondii and Sarcocystis neurona in encephalitic lesions. For proper management and conservation of seals, information on the prevalence of the protozoa, which can be the death of seals, is indispensable. The infection of pathogenic protoz...

ABSTRACT. For proper management and conservation of the Kuril harbor seal (Phoca vitulina stejnegeri) through disease control, serological analysis was performed for influenza A virus infection in free-ranging seals in Hokkaido, Japan. Serum samples were collected from seals at Nosappu (231 seals), Akkeshi (16) and Erimo (75), between 1998 and 2005, and were analyzed by ELISA. Antibodies to the influenza A virus were detected only in seals from Nosappu. The incidences were 11% (1/9), 3% (2/66), 12% (7/59) and 6% (5/77) in 1998, 2003, 2004 and 2005, respectively. These suggest sporadic infection. Because antibody-positive seals included juvenile seals in each year, the infections were considered to have been circulated since no later than the late 1990s until recent years. ELISA-positive sera were analyzed by hemagglutination inhibition (HI) tests to determine the subtypes. Antibodies to the H3 and H6 subtypes were detected in 10 and 2 sera, respectively. Two of the sera that had antibodies to the H6 subtype also had antibodies to the H3 subtype. These two seals were considered to have been infected with both the H3 and H6 subtypes. This is the first investigation to find antibodies to the H6 subtype in seals. Although the H6 subtype had been isolated only from avians, genetic analysis had suggested that the H6 subtype could become a novel mammalian pathogen. For definitive diagnosis, detection of the virus from the tissue or mucus of seals is required. KEY WORDS: H6 subtype, influenza A virus, Japan, Phoca vitulina stejnegeri, seroepidemiology.