Ranaviruses are a group of viruses that are found worldwide. There are different strains of ranavirus including some strains that can cause severe infections and mortality in amphibians, reptiles and fish. Strains that infect amphibians can cause significant mortality in both tadpoles and adults. In the United States, ranavirus has been identified in mortality events in over 25 states in 20 different species of turtles and amphibians. In Wisconsin, infection with ranavirus was identified as the cause of mortality in bullfrog tadpoles and adults in Vilas County in 2014 and in green frog tadpoles and adults in Dane County in 2019. Detection of the virus is likely underestimated due to amphibian and reptile mortalities being less detectable and the challenge of obtaining suitable samples for diagnostic testing.
The virus can be transmitted through direct contact, contaminated water or soil or ingestion of infected animal tissue or other contaminated material.
Infected amphibians may be observed with abnormal behavior such as lethargy, weak or erratic swimming, buoyancy problems or gasping for air. The abdomen or hind legs may appear swollen due to an accumulation of fluid under the skin. There may also be redness of the skin from hemorrhage especially near the hind limbs. In turtles, clinical signs include weakness, swollen eyelids, discharge from the nose and mouth, ulcers on the feet and dull white or thick yellow plaque inside the oral cavity.
Ranaviruses are highly persistent and can remain infectious in the environment for an extended period of time, likely surviving for months in water under favorable conditions.
When sick or dead amphibians (tadpoles, salamanders, frogs) are observed, care should be taken to prevent potentially moving any infectious diseases to another location. At a minimum, rinse off footwear and either air dry in the sun for a few days, disinfect with a 10% bleach solution or wipe off with 70% alcohol wipes before wearing to another water area. Water from home aquariums should be disinfected prior to disposal.
There is no known risk to people or pets.