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Diseases of Aquatic Organisms

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DAO 40:195-201 (2000)  -  doi:10.3354/dao040195

Ichthyophonus-like infection in wild amphibians from Québec, Canada

Igor Mikaelian1,*, Martin Ouellet2, Bruce Pauli3, Jean Rodrigue4, John C. Harshbarger5, David M. Green2

1Canadian Cooperative Wildlife Health Centre and Centre Québécois sur la Santé des Animaux Sauvages, 3200 rue Sicotte, Saint-Hyacinthe, Québec J2S 7C6, Canada
2Redpath Museum, McGill University, 859 Sherbrooke St. West, Montréal, Québec H3A 2K6, Canada
3Canadian Wildlife Service, National Wildlife Research Centre, 100 Boulevard Gamelin, Hull, Québec K1A 0H3, Canada
4Service Canadien de la Faune, 1141 Route de l¹Église, Sainte Foy, Québec G1V 4H5, Canada
5Registry of Tumors in Lower Animals, The George Washington University, Department of Pathology, 2300 I St. NW, Washington, DC 20037, USA
*Present address: IDEXX Veterinary Services, 2825 Kovr Drive, West Sacramento, California 95605, USA. E-mail:

ABSTRACT: Myositis associated with infection by Ichthyophonus-like organisms was diagnosed in 35 of 260 (13%) wild amphibians collected in Québec, Canada, from 1959 to 1964 (n = 30), and 1992 to 1999 (n = 230). Infection was diagnosed in 17 green frogs Rana clamitans, 9 wood frogs R. sylvatica, 4 red-spotted newts Notophthalmus viridescens, 3 bullfrogs R. catesbeiana, 1 spring peeper Pseudacris crucifer, and 1 pickerel frog R. palustris. The spring peeper and one of the bullfrogs were collected in 1964 from the Mont Saint-Hilaire Biosphere Reserve, indicating long-term presence of the organism. Spores of the organisms invaded striated muscle fibers and were associated with variable degrees of granulomatous and eosinophilic inflammation. Infection was considered fatal in 2 green frogs, 1 wood frog, and 1 red-spotted newt. It was considered potentially significant in 3 additional green frogs in which up to 100% of the fibers of some muscles were replaced by spores associated with a severe granulomatous reaction. Ultrastructural features of Ichthyophonus-like spores included a thick trilaminated wall, a paramural cytoplasm, multiple nuclei, oval mitochondria with short tubulo-vesicular cristae and numerous ribosomes. This report represents 4 new host records and shows that ichthyophonosis is enzootic in amphibians from Québec.

KEY WORDS: Amphibian · Anuran · Eukaryotic protist · Ichthyophonosis · Pathology

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