Morbillivirus ecology in polar bears (Ursus maritimus)

Polar bear (Ursus maritimus) morbillivirus infection was initially reported by Follmann and co-workers in 1996, based upon serologic results using can ine distemper virus (CDV). The impetus for the evaluation of polar bear pop ulations for morbillivirus infections was prompted by epidemics of canine d istemper-like disease in seal populations in the north Atlantic regions of Greenland, Europe, and Russia. Since marine morbilliviruses have been furth er characterized into three major species, phocine distemper virus (PDV), d olphin morbillivirus (DMV) and porpoise morbillivirus (PMV), it was of valu e to determine the origin of the polar bear infection. One hundred serum sa mples were selected from a group of sera collected from regions of Alaska a nd Russia and tested by differential serum neutralization assay against the three major marine morbilliviruses and CDV, to determine the predominant v irus infecting the polar bear. Polar bears had higher serum antibody titers to CDV than they did to PDV, DMV, and PMV. These data suggest that polar b ears are being infected with a morbillivirus of terrestrial origin. Further more, based on the high serum antibody prevalence in the population, the vi rus may be indigenous to the polar bear and not necessarily the result of i nterspecies transmission from other arctic mammals susceptible to CDV and/o r marine morbilliviruses.