Unusual causes of fatal upper aerodigestive tract obstruction in wild Bottlenose Dolphins (Tursiops aduncus)

Abstract

Necropsy examination of dolphins living in Gulf St Vincent, Australia is routinely undertaken to enable the evaluation of disease processes and to provide rapid medicolegal assessment of any inflicted and/or accidental injuries. Two Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) are reported to demonstrate conditions that may result in unexpected death involving upper airway compromise by quite unusual mechanisms. In the first case an adult male was found with extensive soft tissue trauma suggesting human interaction. At necropsy, death was due instead to upper airway obstruction from an impacted Slender-spined Porcupine Fish (Diodon nichthemerus) in the posterior pharynx and upper esophagus. In the second case, an adult male dolphin was found to have died, following several weeks' illness, from upper airway obstruction due to extensive respiratory tract papillomatosis within the blowhole. Given the infectious etiology of this condition the local population will be monitored for similar lesions. These cases demonstrate rare causes of upper airway obstruction in wild dolphins that were identifiable only after detailed necropsy examination. The possibility of human involvement in the deaths could be excluded.