Meeting Abstract
Ranavirus is a global pathogen of ectothermic vertebrates that can cause the mass-mortality of entire amphibian communities. However, asymptomatic amphibians have also tested positive for ranavirus in the field. In ephemeral wetland systems, it has been hypothesized that reservoir species retain sublethal infections from year-to-year between pond-filling events and subsequently reintroduce ranavirus to the community. Yet, our understanding of sublethal infection prevalence and the ways in which sublethally-infected individuals impact disease transmission is poor. Our objectives were to 1) explore disease susceptibility at low doses of ranavirus exposure and 2) examine the potential for chronic sublethal ranavirus infection. We conducted a series of laboratory dose-response experiments using Pseudacris ornata, Lithobates capito, and Ambystoma talpoideum. For each species, larvae were assigned to one of four doses ranging from 0 to 103 plaque-forming units of a local strain of ranavirus. Between one to two months after exposure, we sacrificed the survivors and dissected liver tissue for DNA extraction and qPCR. We found interspecific variability in susceptibility to low doses of ranavirus. Across doses, only P. ornata and L. capito larvae showed symptoms of ranavirus (hemorrhaging and acute death). Exposure to 102 plaque-forming units of ranavirus or fewer resulted in only 7% survival of P. ornata, but ~77% survival of L. capito and 100% survival of A. talpoideum. Ranavirus was not detected in the liver tissue of any surviving individuals, regardless of dose or species, suggesting resistance to infection, or the ability to clear the pathogen following infection. Although we found no evidence for chronic sublethal ranavirus infection, the growing documentation of apparently healthy, ranavirus-positive amphibians warrants further investigation of amphibian ranavirus reservoirs.
