Hoverman Jason T, Gray Matthew J, Miller Debra L
Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, University of Tennessee, 274 Ellington Plant Sciences Building, Knoxville, Tennessee 37996-4563, USA.
Dis Aquat Organ. 2010 Mar 9;89(2):97-107. doi: 10.3354/dao02200.
Ranaviruses are responsible for widespread amphibian die-offs, particularly with larval anurans. To understand the factors that may be contributing to the emergence of ranaviruses, we conducted 3 experiments that exposed 3 species of larval anurans to either endemic frog virus 3 (FV3) or an FV3-like isolate from a ranaculture facility. Our goals were to (1) determine the susceptibility of each species to each virus, (2) determine whether direct ingestion of virions or exposure to virions in a water bath were similarly lethal routes of transmission, and (3) quantify the effects of exposure duration on disease outcomes. We conducted our research in a controlled aquatic laboratory using a factorial combination of virus isolates, transmission routes, and exposure durations. While ranaviruses can affect many species, we found that larval anurans differ greatly in susceptibility to ranaviruses. Average mortality rates of Cope's gray tree frogs (66%) and pickerel frogs (68%) were similar but 3-fold higher than for eastern narrow-mouthed toads. Direct ingestion of the viruses increased mean infection and mortality rates by 30% and caused death about 2 times faster compared to water bath exposure. However, exposure duration did not impact mean infection or mortality rates. We also found that the ranaculture isolate increased mortality by > 34% compared to FV3. Our results suggest that ranaviruses can rapidly infect and cause disease in multiple amphibian species. Given the risk associated with introducing novel ranaviruses from ranaculture facilities, we recommend that all nations adopt the protocol set forth by the World Organization for Animal Health for testing and certifying that amphibians that are commercially shipped are negative for ranavirus infection.
蛙病毒对两栖动物的大量死亡负有责任，尤其是对蛙类幼体。为了解可能导致蛙病毒出现的因素，我们进行了3项实验，将3种蛙类幼体暴露于地方性蛙病毒3（FV3）或一种来自蛙类养殖设施的FV3样分离株。我们的目标是：（1）确定每种蛙类对每种病毒的易感性；（2）确定直接摄入病毒粒子或在水浴中接触病毒粒子是否为同样致命的传播途径；（3）量化暴露持续时间对疾病结果的影响。我们在一个受控的水生实验室中进行研究，采用病毒分离株、传播途径和暴露持续时间的析因组合。虽然蛙病毒可影响许多物种，但我们发现蛙类幼体对蛙病毒的易感性差异很大。科普氏灰树蛙（66%）和食蚊蛙（68%）的平均死亡率相似，但比东部窄口蟾蜍高出3倍。与水浴暴露相比，直接摄入病毒使平均感染率和死亡率提高了30%，并使死亡速度加快约2倍。然而，暴露持续时间并未影响平均感染率或死亡率。我们还发现，与FV3相比，来自蛙类养殖设施的分离株使死亡率增加了34%以上。我们的结果表明，蛙病毒可在多种两栖动物物种中迅速感染并引发疾病。鉴于从蛙类养殖设施引入新型蛙病毒存在风险，我们建议所有国家采用世界动物卫生组织制定的规程，对商业运输的两栖动物进行检测和认证，确保其蛙病毒感染呈阴性。
