NSF Award
2438615
Amphibians worldwide are experiencing unprecedented population losses, with some scientists wondering if the earth is at the beginning of the 6th mass extinction. Infectious diseases are a significant threat to amphibian survival. Ranavirosis is caused by Frog Virus 3 (FV3), and causes disease and death in wild and captive amphibians worldwide. FV3 infections of wild tadpoles often result in die-offs of populations reaching close to 100% mortality, a rate that significantly impacts the stability of future wild frog populations. If RV3 moves into captive amphibian populations, it jeopardized breeding programs of endangered species. There must be an understanding of FV3’s pathogenesis (how infection develops in the host) to mitigate ranavirosis. Pathogenesis of FV3 is influenced by many things including: the amphibian’s immune response to infection, and environmental factors linked to the amphibian’s life history, such as sharing habitat with species that serve as virus reservoirs (carriers) or living under unfavorable conditions. This CAREER award will investigate the pathogenesis of FV3 in wood frogs, a native frog species severely affected by outbreaks of ranavirosis. It focuses on the frog’s response to infection, the effects of environment (temperature changes), stress, and presence carriers on infection outcomes. This research funds basic research whose findings will inform decisions in management of wild and captive amphibians. Training of graduate students in this research area will also prepare the next generation of STEM researchers for the workforce. In addition, there are outreach activities to inform the general public about FV3 and frogs to help educate people about current threats to wildlife.<br/><br/><br/>TECHNICAL OVERVIEW<br/><br/>It is theorized that FV3 introduction into a naïve population of wood frogs (Rana sylvatica) will result in local extinction within 5 years. The investigator’s central hypothesis is that the life history (biology and ecology) of the host, its immune response, and the environment it inhabits will determine the outcome of FV3 infection. The PIs previous work found that survivors of sublethal FV3 infections (like green frogs, Rana clamitans) may become long-term carriers of the virus. Thus, environments with green frogs may be associated with ranavirosis tadpole mortalities in wild populations. The proposed research will determine the pathogenesis of infection in tadpoles, disentangle the relationship between (putatively) resistant species (green frogs) and highly susceptible ones (wood frogs); determine if long-term carriers develop when individuals survive infection; characterize the cellular and/or humoral immune response to FV3 infection in adult wood frogs; and determine whether subclinical disease provides protection to re-infection. The work will involve experimental infections of wild-caught, lab-raised, tadpoles and adults, determination of LD50 doses, histopathological examination of affected animals, application of immunohistochemical and molecular labeling (in situ hybridization) techniques to detect target cells/tissues, hematological evaluation of cellular and humoral immune responses, and determination of the effect of corticosteroids on those responses.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
