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Unusual bottlenose dolphin mortality event in the Swan Canning River Park, Western Australia

Stephens, N., Holyoake, C., Finn, H., Patterson, T., Wang, J., Bingham, J., Ha, W., Bejder, L. and Duignan, P. (2012) Unusual bottlenose dolphin mortality event in the Swan Canning River Park, Western Australia. In: 61st International Conference of the Wildlife Disease Association, 22 - 27 July, Lyon, France.

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From June to October 2009 six bottlenose dolphins (Tursiops aduncus) were found dead in the Swan-Canning Estuary, Perth. Opportunistic bacterial and mycotic infections, severe ulcerative dermatitis, and lymphoid depletion suggested reduced immune competence. Ulcerative dermatitis was associated with intracytoplasmic eosinophilic inclusions typical of cetacean poxvirus. Morbillivirus antigen was detected by immunohistochemistry in lymphocytes, endothelium and biliary epithelium from two dolphins. We hypothesize that morbillivirus-induced immunosuppression exacerbated poxvirus dermatitis causing unusually severe ulcerative dermatitis and predisposed to bacterial and Aspergillus spp. infections. Blubber toxicology also found high levels of pollutants such as dieldrin (mean: 17.13 µg/g lipid). Temporal analysis of this event and historical records found an association between mortalities and seasonal flushing of the estuary by heavy spring rains and marked salinity declines. It appears that the Swan-Canning Estuary dolphin population is regulated by a balance between pathogens, environmental stressors and possibly, anthropogenic pollutants.

Item Type: Conference Item
Murdoch Affiliation(s): School of Biological Sciences and Biotechnology
School of Veterinary and Biomedical Sciences
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