Bowater et al., 2003:

"Necropsies were performed on four S. chinensis to determine cause of death. Laboratory tests including serology, bacteriology, histopathology and transmission electron microscopy were done on the four dolphins. Immunohistochemistry was done on the brain, heart, liver, lung, spleen and adrenal gland from various dolphins to detect Toxoplasma gondii antigens.

Necropsies showed all of four S. chinensis that stranded in Queensland in 2000 and 2001 had evidence of predatory shark attack and three were extremely emaciated. Histopathological examinations showed all four dolphins had toxoplasmosis with tissue cysts resembling T. gondii in the brain.

Tachyzoite stages of T. gondii were detected in the lungs, heart, liver, spleen and adrenal gland, variously of all four dolphins. Electron microscopy studies and immunohistochemistry confirmed the tissues cysts were those of T. gondii. All four dolphins also had intercurrent disease including pneumonia, three had peritonitis and one had pancreatitis.

Four S. chinensis necropsied in Queensland in 2000 and 2001 were found to be infected with toxoplasmosis. It is uncertain how these dolphins became infected and further studies are needed to determine how S. chinensis acquire toxoplasmosis. All four dolphins stranded after periods of heavy rainfall, and coastal freshwater runoff may be a risk factor for T. gondii infection in S. chinensis. This disease should be of concern to wildlife managers since S. chinensis is a rare species and its numbers appear to be declining."

T. gondii is a protozoan parasite of worldwide distribution that infects homeothermic animals including primates, marsupials, birds, rodents, other mammals and humans.

The authors findings from histopathological examination of tissues and electron microscopy are similar to other reported cases of toxoplasmosis in marine mammals, in that T. gondii tissue cysts were detected in the brain, and T. gondii tachyzoites, in association with focal necrosis, were detected in various other body organs.  

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Citation and/or URL

Bowater, R., Norton, J., Johnson, S., Hill, B., O'Donoghue, P. & Prior, H. 2003, Toxoplasmosis in Indo-Pacific humpbacked dolphins (Sousa chinensis), from Queensland. Australian Veterinary Journal, 81: (10) 627-632

Spatial Coverage

Townsville and Gladstone 

Temporal Coverage

2000 - 2001

Update Frequency

Not applicable 

Other Information

None