IMPAIRED IMMUNITY IN HARBOR SEALS (PHOCA-VITULINA) FED ENVIRONMENTALLY CONTAMINATED HERRING

In recent years, mass mortalities among seals and dolphins have been a ttributed to infections with different morbilliviruses, In all cases, these marine top predators were exposed to high levels of persistent l ipophilic environmental contaminants accumulated through the food chai n, This observation led to the hypothesis that a contaminant-related s uppression of the immune system might have contributed to the severity of the virus outbreaks, We conducted a semi-field feeding experiment, in which we fed two groups of harbour seals (Phoca vitulina) fish wit h different levels of contaminants. During a period of 21/2 years, blo od samples were taken at regular intervals, and the functioning of dif ferent compartments of the immune system was monitored and compared, W e found impaired natural killer (NK) and specific T cell responses in the seals fed contaminated fish. This is the first demonstration of im munosuppression in mammals following chronic exposure to environmental contaminants at ambient environmental levels.