Harp Elizabeth M, Petranka James W
Department of Biology, University of North Carolina at Asheville, One University Heights, Asheville, North Carolina 28804, USA.
J Wildl Dis. 2006 Apr;42(2):307-18. doi: 10.7589/0090-3558-42.2.307.
Members of the genus Ranavirus (family Iridoviridae) can cause catastrophic mortality of pond-breeding amphibians and are associated with an emerging infectious disease that may be contributing to amphibian declines. We conducted three experiments to examine factors that may affect transmission both within and between local breeding populations of the wood frog (Rana sylvatica). In a laboratory study, when exposed to moribund tadpoles collected during a local ranaviral die-off, uninfected tadpoles died as soon as 4 days after exposure. The onset of death was accelerated when tadpoles were allowed to scavenge on carcasses of infected tadpoles. In a mesocosm experiment that was conducted in outdoor wading pools, die-offs of tadpoles began approximately 19 days after infected tadpoles were added to pools containing uninfected tadpoles. Mass die-offs with greater than 98% mortality occurred in all pools, regardless of the initial tadpole density. In a second mesocosm experiment, the addition of water and bottom sediments that were collected from a pond during a ranaviral die-off did not result in lower tadpole survival or growth relative to controls. Only a small percentage of tadpoles appeared to be sick, and most tadpoles survived until the first individuals began metamorphosing within a pool. However, tests for ranavirus using polymerase chain reaction were positive for most pools that received contaminated sediment, suggesting that some infections were sublethal. Our results indicate that transmission within ponds is enhanced by scavenging and that spread between local ponds could occur via the transport of contaminated sediment by animals or humans.
蛙病毒属（虹彩病毒科）的成员可导致池塘养殖两栖动物的灾难性死亡，并与一种新兴传染病相关，这种传染病可能是两栖动物数量减少的原因之一。我们进行了三项实验，以研究可能影响林蛙（Rana sylvatica）当地繁殖种群内部和之间传播的因素。在一项实验室研究中，当未感染的蝌蚪接触在当地蛙病毒死亡事件期间收集的濒死蝌蚪时，它们在接触后4天就死亡了。当允许蝌蚪啃食感染蝌蚪的尸体时，死亡开始时间加快。在一项在室外浅水池中进行的中宇宙实验中，在将感染的蝌蚪添加到含有未感染蝌蚪的水池中后，大约19天蝌蚪开始死亡。所有水池都发生了死亡率超过98%的大规模死亡，无论初始蝌蚪密度如何。在第二项中宇宙实验中，添加从发生蛙病毒死亡事件的池塘中收集的水和底部沉积物，与对照组相比，并未导致蝌蚪存活率或生长率降低。只有一小部分蝌蚪似乎生病，大多数蝌蚪存活到水池中的第一批个体开始变态。然而，使用聚合酶链反应对蛙病毒进行检测时，大多数接受受污染沉积物的水池呈阳性，这表明一些感染是亚致死性的。我们的结果表明，啃食会增强池塘内的传播，并且当地池塘之间的传播可能通过动物或人类运输受污染的沉积物而发生。
