Rayle Maya R, Brunner Jesse L, Dahrouge Nicole C, Keller Erin L, Rittenhouse Tracy A G
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA.
School of Biological Sciences, Washington State University, Pullman, WA, 99163, USA.
Oecologia. 2025 Mar 4;207(3):46. doi: 10.1007/s00442-025-05682-8.
Ranaviruses are responsible for mass die offs of wood frog (Lithobates sylvaticus) tadpoles. What happens in between epidemics is less clear, but juvenile (metamorphosed) stages are hypothesized to move Ranaviruses among wetlands and introduce or reintroduce these viruses into wetlands, initiating new outbreaks. A key question is under what circumstances can juvenile L. sylvaticus infect susceptible conspecifics. We examined Ranavirus transmission between juvenile L. sylvaticus in two settings: first, we measured transmission from a Ranavirus-infected frog to a co-housed susceptible frog via cohabitation over a range of exposure periods. Second, we measured indirect transmission to susceptible frogs from a contaminated environment after a range of waiting times (i.e., from when the infected frog was removed to when the susceptible frog was exposed to the environment). We present evidence that juvenile frogs directly transmitted Ranavirus to susceptible frogs in all exposure periods (99.2% infected), with as little as 1 h of co-housing resulting in 95.8% of susceptibles infected. Indirectly, 96.8% of susceptible frogs became infected after as long as 48 h waiting times. Neither exposure period nor wait times influenced the probability of infection, because these probabilities are already high. In our linear regression models, susceptible frog viral load was significantly correlated with exposure period and cohort for the cohabitation experiment, while wait time was significantly correlated with viral load for the sequential habitation experiment. Collectively, our results suggest that Ranavirus transmission readily occurs between recently metamorphosed wood frogs and via terrestrial environmental exposure.
蛙病毒属病毒是导致林蛙（Lithobates sylvaticus）蝌蚪大量死亡的原因。在疫情爆发期间所发生的情况尚不太清楚，但据推测，处于幼体（已变态）阶段的林蛙会在湿地之间传播蛙病毒属病毒，并将这些病毒引入或重新引入湿地，从而引发新的疫情。一个关键问题是，在何种情况下，幼年林蛙能够感染易感的同种个体。我们在两种环境下研究了蛙病毒属病毒在幼年林蛙之间的传播情况：首先，我们测量了在一系列暴露时间段内，从感染蛙病毒属病毒的青蛙通过同居方式将病毒传播给同笼饲养的易感青蛙的情况。其次，我们测量了在一系列等待时间后（即从移除感染青蛙到易感青蛙接触该环境的时间），受污染环境对易感青蛙的间接传播情况。我们提供的证据表明，在所有暴露时间段内，幼年青蛙都能将蛙病毒属病毒直接传播给易感青蛙（感染率为99.2%），同居仅1小时就导致95.8%的易感青蛙被感染。间接传播方面，长达48小时的等待时间后，96.8%的易感青蛙被感染。暴露时间段和等待时间均未影响感染概率，因为这些概率已经很高。在我们的线性回归模型中，在同居实验中，易感青蛙的病毒载量与暴露时间段和群体显著相关，而在连续居住实验中，等待时间与病毒载量显著相关。总体而言，我们的结果表明，蛙病毒属病毒很容易在刚变态的林蛙之间传播，并且可通过陆地环境暴露传播。
