In 2009 two adult female bottlenose dolphins were found dead within the Swan-Canning Estuary. Both dolphins had severe ulcerative skin lesions covering over 70% of their skin surface area. Histological analyses identified viral inclusion bodies characteristic of poxvirus within these skin lesions. The severity and extent of the lesions were deemed to have caused terminal debilitation in the two dolphins. Infection with dolphin poxvirus is usually characterised by one to several mild skin lesions in juveniles that regress with time. Poxvirus infection has never been documented as the cause of death in adult dolphins; furthermore the severe skin lesions observed in the two dolphins mark a novel presentation of dolphin poxvirus infection. The definitive mechanisms by which the characteristic poxvirus lesions may have progressed to the unusually severe lesions is currently unknown but possible factors may include: the presence of a poxvirus strain possessing greater virulence; and/or the potentially immunosuppressive effects associated with living in a heavily utilised and inherently stressful estuarine environment. Dolphins are recognised as biosentinels for coastal and estuarine ecosystems, and atypical disease presentations such as this may be indicative of the environmental conditions of systems like the Swan-Canning Estuary
