Detection of ranavirus in five amphibian species among three Ohio ponds

Background/Question/Methods In Spring 2012, dip netting of Taylor-Ochs Pond, a long-term study site, revealed mass mortality of pre-metamorphic Lithobates sylvaticus, L. clamitans, and Ambystoma maculatum. We tested samples of all three species as well as apparently well samples of sympatric Anaxyrus americanus for ranavirus. Another 49 A. americanus larvae were maintained in the lab for 21 days and subsequently tested for ranavirus to determine infection and mortality rates. Finally, to further identify the distribution of ranavirus in the area, we tested larvae for ranavirus from one upstream and three downstream ponds. 

Results/Conclusions All individuals from our initial Taylor-Ochs Pond sample tested positive for ranavirus. Within those samples, moribund larvae had a higher virus titer than those that were apparently well. Additionally, among apparently well individuals, L. clamitans had significantly higher mean virus titers than A. maculatum, A. americanus, and L. sylvaticus, but there was no difference in virus titers among moribund individuals of different species. Among the lab-maintained A. americanus, 16% tested positive for ranavirus, and infected individuals experienced a significantly lower survivorship than did uninfected individuals. Finally, ranavirus was detected in two of the four nearby ponds. In conclusion, ranavirus has been identified for the first time in a pond that has been studied thoroughly for eight years. The presence of ranavirus may have differential effects on the members of the pond-breeding amphibian community that rely on this pond and several nearby ponds. Further observation of Taylor-Ochs and surrounding ponds should provide better information on the longer-term consequences of this new threat.