Table 1.
Summary of species, age and tissue samples examined.
Table 2.
Seasonal prevalence of Cystodiscus axonis plasmodia, Cystodiscus spp. liver plasmodia and hepatic myxosporidiosis in Green and golden bell tadpoles.
Figure 1.
Cystodiscus axonis lesions in brains of Green and golden bell frogs and tadpoles.
A. Root nerve of a Green and golden bell tadpole showing severe inflammation, loss of nerve ganglia and numerous C. axonis plasmodia (arrowheads), scale 200 µm; B. Higher magnification (20X view) of root nerve (A), infiltrate has completely replaced nerve cells, scattered foci of necrosis are seen throughout the nerve (circle), scale 100 µm; C. Higher magnification view of C. axonis plasmodia within the same nerve root (A) (40X), scale 50 µm; D. Posterior end of Green and golden bell metamorph spinal cord showing moderate glial activity in response to moderate plasmodia load (arrowheads indicate plasmodia). This animal had motor dysfunction possibly due to the high load of plasmodia in its spinal cord and dorsal nerve roots, scale 200 µm; E. Moderate load of plasmodia (arrows) in diencephalon and mesencephalon of tadpole, scale 200 µm; F. Higher magnification (20X) view of plasmodia in diencephalon of tadpole (E) showing increased glial activity in response to plasmodia presence, scale 40 µm.
Figure 2.
Severe reactions to Cystodiscus axonis plasmodia in other species of Australian frogs.
A. Spinal cord of Southern bell frog showing multifocal and locally extensive gliosis in reaction to moderate load of C. axonis plasmodia (arrows), individual was noted to be lethargic and inappetent, scale 200 µm; B. Spinal cord of Southern bell frog showing congestion and severe haemorrhage in association with high numbers of C. axonis plasmodia, individual was found dead, scale 50 µm; C. Diffuse haemorrhage, multifocal melacia (grey arrowheads) and gliosis and C. axonis plasmodia (black arrowheads) in spinal cord of Yellow spotted bell frog, scale 100 µm; D. C. axonis plasmodia associated with blood vessel epithelial cell in Yellow spotted bell frog spinal cord, scale 20 µm; E. Cross section of Booroolong frog infected with C. axonis, showing severe haemorrhage, extensive multifocal gliosis and spongiform change, scale 100 µm; F. Nerve root of Striped marsh frog showing mild focal gliosis in association with C. axonis plasmodia (arrow), scale 50 µm.
Figure 3.
Myxosporiodiosis and developing Cystodiscus spp. plasmodia in tadpoles.
A. Coalescing extensive biliary lesions in Green and golden bell tadpole, scale 500 µm; B. Green and golden bell tadpole showing loss of hepatocytes surrounding hyperactive biliary tree and lymphoplasmacytic inflammation, moderate grade of hepatic myxosporidiosis, scale 200 µm; C. Mild inflammation and biliary hyperplasia seen in Striped marsh tadpole, scale 100 µm; D. Higher magnification of Cystodiscus spp. (either C. axonis or C. australis) intra-biliary plasmodium, scale 25 µm; E. Peron's tree frog tadpole with moderate hepatic myxosporidiosis and plasmodia development in gallbladder (free floating forms), scale 200 µm; F. higher magnification view of plasmodia in (E) (40X), plasmodia appear vacuolated and with scattered nuclei in cytoplasm, these are immature forms (presporogonic) of Cystodiscus spp. that develop in the gallbladder, scale 40 µm.
Figure 4.
Cystodiscus spp. liver and gallbladder development in adult frogs.
A. Normal portal triad in healthy adult Striped marsh frog, scale 50 µm; B. Moderate hepatic lesions in Southern bell frog adult with C. axonis myxospores in gallbladder, moderate biliary hyperplasia, fibrosis and inflammation. No intra-biliary plasmodia were seen, scale 100 µm; C. Severe biliary fibrosis in adult Peron's tree frog infected with C. axonis myxospores in gallbladder. No plasmodia within bile ducts, calcified deposits observed within biliary tree (also seen in tadpoles), scale 500 µm; D. Intrabiliary C. axonis plasmodia in sub-adult Yellow spotted bell frog, bile duct extremely distended, surrounded by lymphoplamacytic infiltration and some fibrosis, scale 100 µm; E. Cystodiscus axonis plasmodia in adult Booroolong frog bile duct, mild biliary hyperplasia and inflammation accompanied the infection, scale 20 µm; F. Myxospores (arrowheads) in the gallbladder of adult Cane toad, spores identified by circular polar capsules at distal ends, found throughout large plasmodium cytoplasm and freely in bile, scale 40 µm.
Table 3.
Comparison of detection method results (single histological section vs. serial histological sections) and species specific multiplex PCR.