Five amphibian mortality events associated with ranavirus infection in south central Ontario, Canada.

Using field, molecular and histological methods, an epizootic, systemic disease causing death within wood frog Rana sylvatica tadpoles and leopard frog Rana pipiens metamorphs at 3 different locations within Southern Ontario, Canada, has been investigated. Our results demonstrated that the probable cause of this disease was a ranavirus. Affected amphibians were found to exhibit necrosis within the hematopoietic cells. Liver tissue samples were found positive for the virus by PCR amplification of the ranavirus (Family: Iridoviridae) major capsid protein (MCP). Positive samples were confirmed by sequence analysis. Clinically normal, laboratory-raised wood frog egg broods were also found to test weakly positive for ranavirus. The population effects of disease on these amphibian communities have not yet been conclusively associated with population declines, but warrant more focused consideration.