MORBILLIVIRUS INFECTIONS OF AQUATIC MAMMALS - NEWLY IDENTIFIED MEMBERS OF THE GENUS

Several disease outbreaks, which have caused the deaths of many thousa nds of seals and dolphins during the last decade, have now been attrib uted to infections with newly identified Morbilliviruses. Outbreaks in the late eighties amongst harbour seals (Phoca vitulina) and grey sea ls (Halichoerus grypus) in northwestern Europe and amongst baikal seal s (Phoca sibirica) in Siberia were caused by the newly discovered phoc ine distemper virus and by a strain of canine distemper virus, respect ively. Although closely related these two viruses were not identical. They were more distantly related to the viruses which caused mass mort ality amongst striped dolphins (Stenella coeruleoalba) in the Mediterr anean sea in the early nineties. This dolphin morbillivirus was shown to be closely related to a virus that was found in harbour porpoises ( Phocoena phocoena) which had stranded at the coasts of northwestern Eu rope in the late eighties: porpoise morbillivirus. The present knowled ge of the genetic and antigenic relationships of these apparently new members of the genus Morbillivirus with the established members of the genus is presented. In addition, the origin and epizootiological aspe cts of these newly discovered viruses are discussed. Finally experimen tal evidence that environmental pollution may have contributed to the severity and extent of these infections in recent years is presented.