Impairment of Immune Function in Harbor Seals (Phoca vitulina) Feeding on Fish from Polluted Waters

摘要

textabstractDisease outbreaks with high mortality rates among seals and dolphinshave recently attracted considerable public and scientificinterest. Allhouyh in most cases morbillivirus infections wereshown to be the primary cause of the disease outbreaks, it wasspeculated that pollution-induced immunosuppression had playat:!a contributory role. Here we present results of a prospectivestudy under semifield conditions, in which two groups of harborseals (Phoca vitulina) were fed herring from marine regions withdifferent contamination levels; the highly polluted Baltic Sea andthe relatively unpolluted Atlantic Ocean. During a period of 93weeks, parameters related to immune function were monitoredand compared between the two groups. We found that naturalkiller-cell activity and mitogen-induced proliferative T -cell responsesfrom the seals feeding on herring from the Baltic Seawere significantly lower. In addition, we observed higher levels ofcirculating polymorphonuclear granulocytes in these animals,which may indicate an increase in the occurrence of bacterial infections.This is the first demonstration of impaired immunologicalfunctions in mammals associated with chronic exposure to environmentalcontaminants accumulated through the marine foodchain.