Ranavirus Ecology and Evolution: From Epidemiology to Extinction

Ranaviruses have been identified in wild and captive populations of ectothermic vertebrates around the world. Ranavirus epidemics can result in a range of effects on their host populations, from apparently benign infections to mass mortality and local extirpation. In this chapter, we review the current status of ranavirus epidemiology and ecology in amphibians, fish, and reptiles. Ranavirus epidemics in amphibians and fish usually have a rapid onset in the mid-to-late summer while outbreaks in reptiles occur irregularly. Susceptibility to ranavirus differs among host species, and may be influenced by the type of ranavirus and natural or anthropogenic stressors. Ranaviruses can be transmitted within and between host species via several routes, but there is a need for transmission estimates in natural environments. Generally, ranaviruses are locally adapted to their host populations, but movement of infected hosts over long distances can disrupt these associations. There is evidence of increased virulence of ranaviruses in captive fish and amphibian populations raised for production. Given their broad host ranges, potential for high virulence, multiple routes of transmission, and frequent movement of amphibians, fish and reptiles in global trade, it appears that some ranaviruses have the potential to significantly impact host populations and even cause extinctions in the wild