| Abstract
| - Harbor porpoises from the German North and Baltic Seasexhibit a higher incidence of bacterial infections comparedto whales from less polluted arctic waters. The potentialadverse effect of environmental contaminants such aspolychlorinated biphenyls (PCBs) and heavy metals on theimmune system and the health status of marine mammalsis still discussed controversially. The aim of the present studywas to investigate the possible influence of PCB,polybrominated diphenyl ether (PBDE), toxaphene, (p,p‘-dichlorodiphenyl)trichlorethane (DDT), and (p,p‘-dichlorodiphenyl)dichlorethene (DDE) on the immune system of harborporpoises. Lymphoid organs are influenced by a variety offactors, and therefore special emphasis was given toseparating the confounding effect of age, health status,nutritional state, geographical location, and sex from theeffect of contaminant levels upon thymus and spleen.Contaminant analysis and detailed pathological examinationswere conducted on 61 by-caught and stranded whalesfrom the North and Baltic Seas and Icelandic and Norwegianwaters. Stranded harbor porpoises were more severelydiseased than by-caught animals. Thymic atrophy and splenicdepletion were significantly correlated to increased PCBand PBDE levels. However, lymphoid depletion wasalso associated with emaciation and an impaired healthstatus. The present report supports the hypothesis ofa contaminant-induced immunosuppression, possiblycontributing to disease susceptibility in harbor porpoises.However, further studies are needed to determine iflymphoid depletion is primarily contaminant-induced orsecondary to disease and emaciation in this cetacean species.
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