Ranavirus discovered in Ontario turtles
Ontario’s turtles are remarkably long-lived – some species can live for over a century, and individuals are usually quite resistant to disease. But mortality from Ranavirus has now been confirmed for the first time in two species of turtles in Ontario, in a Snapping Turtle and a Wood Turtle that were examined at the CWHC regional lab. Ranavirus is a member of the Iridovirus group: Iridoviruses are a group of viruses that infect cold-blooded vertebrates, including amphibians, fish and reptiles. Ranavirus has been implicated in die-offs of amphibians, mostly larval and recently metamorphosed frogs, in many locations, including Ontario. However, it has not been previously confirmed causing mortality in Ontario turtles.
The first case involved a Snapping Turtle found sick in mid-summer of 2017 and taken to a wildlife rehabilitation centre. Treatment was unsuccessful and the turtle was euthanized and sent to the CWHC for diagnostic examination. The most striking externally visible lesions were massively swollen eyelids, and necrotic areas in the oral cavity. Histologically, there was extensive necrosis and edema in the eyelids.
The second case was a Wood Turtle with the unusual history of being found out in the snow in January. This young turtle was in poor body condition with very little stored fat available for overwinter survival. Microscopically, there was widespread death of individual cells in the liver.
Tissues from both cases were sent to the British Columbia Animal Health Centre in Abbotsford, where they were tested for of the presence of Ranavirus using a real-time polymerase chain reaction (rtPCR), a very specific diagnostic test for detecting the presence of a particular pathogen. Tissues from both species of turtle tested positive for Ranavirus. Tissues were also tested for Herpesvirus, another virus capable of causing severe lesions and death in turtles. Testing for Herpesvirus was negative in both cases.
Ranavirus has caused mortality of Box Turtles in the USA, but its occurrence and range in the wild are not well understood. These are the first reports of disease due to Ranavirus in wild Snapping and Wood Turtles, and the first reports of Ranavirus occurring in any wild turtles in Ontario. Ranavirus is not uncommon in Ontario, where it has been detected in amphibians at several sites, but the significance of its occurrence in turtles is unclear at this point. It is unknown whether these mortalities represent the beginning of a Ranavirus outbreak in Ontario turtles, or whether Ranavirus is persistent in the environment, sometimes infects turtles, and has only now been detected in wild turtles through the efforts of field researchers who are actively monitoring wild populations. In both of these cases, the affected individuals came from turtle populations that are the subject of long-term scientific studies, making it far more likely that any disease occurrences will be observed and investigated.
Determining the significance of this virus to Ontario turtles will depend on the observation and collection of sick and/or diseased turtles over the next few years. Persons finding live, sick turtles should contact the Ontario Turtle Conservation Centre (705-741-5000) where the turtles can be examined clinically, treated if possible, and have samples collected for further testing. Similarly, dead turtles can be collected and reported to the CWHC (in Ontario 1-866-673-4781), so that arrangements can be made for getting the turtle’s carcass to the laboratory for diagnostic evaluation.
As observations and diagnostic examinations accumulate, we hope to better understand the geographic extent and host species range of this virus, and to evaluate the degree to which it may pose a threat to Ontario’s turtles, many of which are classified as Species at Risk.