A new study conducted by scientists from various research organizations in Russia under the leadership of PhD E.P. Simonov from the Laboratory of Mammalian Microevolution at the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences (IEE RAS) has for the first time revealed the widespread distribution of ranaviruses in green frogs (genus Pelophylax) in Russia. Ranaviruses are capable of causing mass mortality of amphibians and are considered one of the main threats to amphibian biodiversity worldwide. In addition, ranaviruses also affect other ectothermic vertebrates – reptiles and fish.
The scientists analyzed DNA extracted from 853 samples collected between 2006 and 2016, of which 590 were obtained from frogs directly at the capture site or immediately after, and 263 from individuals kept in laboratories after capture for various studies. The results showed that 8.8% of "wild" frogs and 27% of those kept in captivity were infected with ranavirus. However, the frogs in captivity had a significantly higher viral load, which may be due to increased stress and crowding in laboratory conditions.
Ranaviruses were detected in 18 of the 94 locations studied, including the basins of Europe's largest rivers — the Volga, Dnieper, and Don. The scientists paid special attention to invasive populations of the marsh frog (Pelophylax ridibundus) from the Trans-Urals and Western Siberia. Ranaviruses were also detected in five of the nine invasive populations studied, indicating the potential role of the marsh frog in the spread of the virus. At the same time, invasive populations of the species from Kamchatka were not infected.
Sequencing of the DNA sequence of the major capsid protein (MCP) gene revealed six different ranavirus haplotypes, all belonging to the CMTV (common midwife toad virus) lineage. Together with literature data on the spread of CMTV-like ranaviruses in Western and Central Europe, the new data indicate the spread of this ranavirus lineage across the continent.
Previously, ranaviruses were found only in two locations on the map of Russia - in the Moscow region and the environs of Tyumen. Thus, the study emphasizes the importance of monitoring and controlling the spread of ranaviruses, especially in the context of climate change and active movement of animals by humans.
The work was published in the journal EcoHealth: Lisachova L.S., Lisachov A.P., Ermakov O.A., Svinin A.O., Chernigova P.I., Lyapkov S.M., Zamaletdinov R.I., Pavlov A.V, Zaks S.S., Fayzulin A.I., Korzikov V.A., Simonov E. (2025) Continent-Wide Distribution of CMTV-Like Ranavirus, from the Urals to the Atlantic Ocean. EcoHealth
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