Toxoplasmosis in Indo-Pacific humpbacked dolphins (Sousa chinensis), from Queensland.
OBJECTIVE
To describe the clinical signs, gross pathology, serology, bacteriology, histopathology, electron microscopy and immunohistochemistry findings associated with toxoplasmosis in four Indo-Pacific humpbacked dolphins (Sousa chinensis) that stranded in Queensland in 2000 and 2001.


METHODS
Clinical assessment, gross necropsy, and laboratory examinations.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Bowater
R O
RO
Oonoonba Veterinary Laboratory, Queensland Department of Primary Industries, Animal and Plant Health Service, PO Box 1085, Townsville, Queensland 4810.
Norton
J
J
Johnson
S
S
Hill
B
B
O'Donoghue
P
P
Prior
H
H
D000818:Animals; D004289:Dolphins; D007150:Immunohistochemistry / Q000662:veterinary; D008854:Microscopy, Electron / Q000662:veterinary; D011793:Queensland / Q000453:epidemiology; D014122:Toxoplasma / Q000302:isolation & purification / Q000648:ultrastructure; D014124:Toxoplasmosis, Animal / Q000453:epidemiology* / Q000209:etiology / Q000473:pathology