IMPAIRMENT OF IMMUNE FUNCTION IN HARBOR SEALS (PHOCA-VITULINA) FEEDING ON FISH FROM POLLUTED WATERS

Disease outbreaks with high mortality rates among seals and dolphins h ave recently attracted considerable public and scientific interest. Al though in most cases morbillivirus infections were shown to be the pri mary cause of the disease outbreaks, it was speculated that pollution- induced immunosuppression had played a contributory role. Here we pres ent results of a prospective study under semifield conditions, in whic h two groups of harbor seals (Phoca vitulina) were fed herring from ma rine regions with different contamination levels; the highly polluted Baltic Sea and the relatively unpolluted Atlantic Ocean. During a peri od of 93 weeks, parameters related to immune function were monitored a nd compared between the two groups. We found that natural killer-cell activity and mitogen-induced proliferative T-cell responses from the s eals feeding on herring from the Baltic Sea were significantly lower. In addition, we observed higher levels of circulating polymorphonuclea r granulocytes in these animals, which may indicate an increase in the occurrence of bacterial infections. This is the first demonstration o f impaired immunological functions in mammals associated with chronic exposure to environmental contaminants accumulated through the marine food chain.