Publication Abstract

Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales

P.M. Bennett, P.D. Jepson, R.J. Law, B.R. Jones, T. Kuiken, J.R. Baker, E. Rogan and J.K. Kirkwood

We test whether long-term exposure to heavy metals, including immnunosuppressive metals like mercury, is associated with infectious disease in wild cetacean. Post mortem investigation on 86 harbour porpoises Phocoena phocoena found dead along the coasts of England and Wales revealed that 49 of the porpoises were healthy when they died as a consequence of physical trauma (most frequently entrapment in fishing gear). In contrast, 37 porpoises died of infectious diseases caused by parasitic, bacterial, fungal and viral pathogens (most frequently pneumonia caused by lungworm and bacterial infections). We found that mean liver concentrations of Hg, Se and Zn in the porpoises that died of infectious disease were significantly higher than in those that died from physical trauma. Liver concentrations of Pb, Cd, Cu and Cr did not differ between the two groups. Furthermore, the Hg to Se molar ratio was significantly higher in the livers of porpoises that died of infectious disease, suggesting a reduced capacity for the Se-dependent binding of highly toxic methylmercury in these individuals. Excess Hg may have presented a toxic challenge and caused immunosuppression in the porpoises that succumbed to infectious disease. These results support the hypothesis that chronic exposure to Hg influences susceptibility to infectious disease and mortality in harbour porpoises.

Reference:

P.M. Bennett, P.D. Jepson, R.J. Law, B.R. Jones, T. Kuiken, J.R. Baker, E. Rogan and J.K. Kirkwood, 2001. Exposure to heavy metals and infectious disease mortality in harbour porpoises from England and Wales. Environmental Pollution, 112: 33-240