Professor Publishes First Book on Emerging Pathogen Ranavirus

Thousands of dead wood frog tadpoles associated with a ranavirus die-off in Maine (photo credit, Nathaniel Wheelwright)

Thousands of dead wood frog tadpoles associated with a ranavirus die-off in Maine (photo credit, Nathaniel Wheelwright)

A genus of emerging pathogens Ranavirus is thought to be the potential new culprit causing the decline and extinction of amphibians around the world. A new book by a UT professor provides insight on the viruses and guidance on urgent research directions to address them.

Ranaviruses: Lethal Pathogens of Ectothermic Vertebrates was published this month as an Open Access eBook by Springer. It is available online. The lead editor is Matthew Gray, a professor in the Department of Forestry, Wildlife, and Fisheries in the UT Institute of Agriculture.

Last year, Gray and other scientists published research about Ranaviruses through the National Institute for Mathematical and Biological Synthesis (NIMBioS) and the Department of Forestry, Wildlife, and Fisheries’s Center for Wildlife Health. The study investigated the effect of Ranavirus on the entire life cycle of wood frogs in demographically isolated populations, where there is no movement of frogs into the population from surrounding areas. Researchers showed that Ranavirus, which causes severe hemorrhage of internal organs in frogs, could cause extinction of isolated populations of wood frogs if they are exposed to the virus every few years.

The new book, the first published on ranaviruses, addresses the distribution and host range of the viruses, their evolution and ecology, microbiology of the pathogens, host immunity responses, diagnostic procedures, and approaches to design studies on ranaviruses.

Ranaviruses can infect amphibians, fish, and reptiles and evolve quickly. When the virus emerges, it can kill nearly all amphibians in a wetland or pond. The effects on fish and reptiles are less known, but die-offs in eastern box turtles and pallid sturgeon, a federally endangered species, have occurred.

Health assessments of salamanders in the Great Smoky Mountains National Park, where ranavirus outbreaks have occurred; Matthew Gray shows a student how to use a spring scale (photo credit, Todd Amacker Conservation Photography)

Health assessments of salamanders in the Great Smoky Mountains National Park, where ranavirus outbreaks have occurred; Matthew Gray shows a student how to use a spring scale (photo credit, Todd Amacker Conservation Photography)

Gray has been researching the pathogens for ten years after discovering it on the Cumberland Plateau. Since then, outbreaks have been reported in Knox, Blount, and Cocke Counties. Die-offs also have occurred around the globe on every continent where ectothermic vertebrate species exist. International commerce of fish, frogs, and turtles is believed to be contributing to the pathogen’s emergence, because virulent strains are moved across continents and among nations through trade.

An increase in use of pesticides and heavy metals that suppress the immune system of cold-blooded animals also likely plays a role in the die-offs, as does climate change.

Twenty-six experts from four countries participated in writing the book. Gray co-authored three of the eight chapters. The book is a foundational reference for scientists investigating cases of Ranavirus die-offs, and provides essential guidance on urgent research directions.

Open Access publishing was made possible through grants provided by the UT Office of Research and Engagement; Institute of Agriculture AgResearch; and the Department of Forestry, Wildlife, and Fisheries.