An epidemiological study of morbillivirus infection in free-ranging and stranded pinnipeds was carried out between 1980 and 1994. The species (n = 6) were divided into two ecological zones - (1) the Canadian Arctic, and (2) the cold temperate waters of Atlantic Canada and the United States. Walrus (Odobenus rosmarus) and ringed seals (Phoca hispida) are year-round residents in the first zone while harbor (P. vitulina) and gray seals (Halichoerus grypus) are found in the second zone. Two pagophilic species migrate between the two zones - harp (P. groenlandica) and hooded (Cystophora cristata) seals. Among the Arctic and pagophilic species the prevalence of infection was significantly higher in harp seals. Similarly, the prevalence of infection was significantly higher in gray seals than in harbor seals. For all species antibody titer was higher against phocine distemper virus than any other morbillivirus. An outbreak of disease occurred among harbor seals in southern New England and on Long Island, N.Y., during the winter of 1991-92. Although evidence of infection was found in all six pinniped species, the pattern of infection and the average frequency of disease varied between species. We propose that harp and gray seals are important reservoir hosts on the Atlantic coast and that outbreaks of disease may occur periodically among harbor seals.

A serologic survey for morbilli viruses was carried out on Florida manatees, Trichechus manatus latirostris, (n = 148) between 1977 and 1994. Additional sera were obtained from Antillean manatees, T. m. manatus, (n = 12) from Guiana and Amazon manatees, T. inunguis (n = 12). Virus neutralizing antibodies, confirmed by radio-immunoprecipitation studies, were found in six Florida manatees. The samples were collected in different years and from different locations on the east and west coasts of Florida. The data indicate that infection in this species is sporadic and that manatees are most likely a dead-end host. Antibody titers were highest against the cetacean morbilli viruses suggesting that dolphins may have been the source of infection for the manatees.