The Influence of Petrochemicals and Stress on the Immune System of Seabirds
There is increasing attention directed to the role of environmental pollutants in altering immune function. Only with the identification of the responsible environmental toxicants, and an understanding of their mechanisms of action, can we hope to treat immunotoxic injuries. This situation is exemplified by the exposure of wild birds to oil spills, the subsequent potential for direct toxicity from the oil, and the secondary toxicity of stress-induced immune modulation. Immunosuppressive mechanisms related to oil ingestion and handling stress are implicated in the morbidity and mortality of seabirds during care and following reentry into the wild. This does suggest that improvements in the treatment of these affected animals will enhance their survival and well-being. However, a survey of the literature shows that the implementation of better techniques are hampered by inadequate information on the immunological consequences of oil contact with seabirds. Marine oil pollution is a constant occurrence and will continue as long as oil and oil products are important commodities transported by sea routes. Among the numerous negative consequences of oil pollution are its effects on marine wildlife. There is much evidence that oil spills are responsible for massive seabird deaths. However, the constant, low level releases of petrochemicals probably contribute to the harmful effects of oil pollution on seabird populations. In an attempt to rectify the damage inflicted on seabirds by accidental oil discharge, rehabilitation centers are established for the cleaning and care of affected wildlife. Unfortunately, there is evidence that the ingestion of oil by preening and the handling stress undergone by birds in these centers lowers their ability to survive and reproduce following release to their native habitats. Although the reasons for this are unclear, there is the suggestion that both oil and handling will induce immunosuppressive mechanisms that ultimately predispose birds to infections and immune-mediated diseases, as well as reproductive, behavioral, and other problems. Thus, there are questions concerning the effectiveness of intervention measures currently being used in the rehabilitation of seabirds.