comparative pathology and ecological implications of two myxosporean parasites in native australian frogs and the invasive cane toad比较病理学和生态的影响两个myxosporean寄生虫在澳大利亚本土青蛙和甘蔗蟾蜍入侵.pdf

Comparative Pathology and Ecological Implications of Two Myxosporean Parasites in Native Australian Frogs and the Invasive Cane Toad 1 1 2 ˇ 1 1 Ashlie Hartigan , Navneet K. Dhand , Karrie Rose , Jan Slapeta , David N. Phalen * 1 Faculty of Veterinary Science, University of Sydney, New South Wales, Australia, 2 Australian Registry of Wildlife Health, Taronga Conservation Society Australia, Mosman, New South Wales, Australia Abstract Myxosporean parasites Cystodiscus axonis and C. australis are pathogens of native and exotic Australian frog species. The pathology and ecological outcomes of infection with these parasites were investigated in this study. Gliosis was correlated to Cystodiscus axonis plasmodia in the brains of (9/60) tadpoles and (3/9) adult endangered Green and golden bell frogs using ordinal regression. Severe host reactions to C. axonis (haemorrhage, necrosis, and vasulitis) were observed in the brains of threatened Southern bell frogs (8/8), critically endangered Booroolong frogs (15/44) and Yellow spotted bell frogs (3/3). Severe brain lesions were associated with behavioural changes, neurological dysfunction, and spontaneous death. Both C. axonis and C. australis develop in the bile ducts of tadpoles, the plasmodia were significantly associated with biliary hyperplasia, inflammation and the loss of hepatocytes in (34/72) Green and golden bell frog tadpoles using ordinal regression. These lesions were so severe that in some cases 70% of the total liver was diseased. Normal liver function in tadpoles is necessary for metamorphosis, metabolism, and immune function. We postulate that this extensive liver damage would have significant host health impacts. Severe hepatic myxosporidiosis was m