Gray Matthew J, Miller Debra L, Schmutzer A Chandler, Baldwin Charles A
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. 2007 Sep 14;77(2):97-103. doi: 10.3354/dao01837.
Ranaviruses have been associated with most of the reported larval anuran die-offs in the United States. It is hypothesized that anthropogenically induced stress may increase pathogen prevalence in amphibian populations by compromising immunity. Cattle use of wetlands may stress resident tadpole populations by reducing water quality. We isolated a Ranavirus from green frog Rana clamitans (n = 80) and American bullfrog R. catesbeiana (n = 104) tadpoles collected at 5 cattle-access and 3 non-access wetlands on the Cumberland Plateau, Tennessee, USA. Sequencing confirmed Frog virus 3 (FV3); therefore, we compared its prevalence between tadpole populations inhabiting cattle-access and non-access wetlands, and among 3 seasons (winter, summer, and autumn) in 2005. We found FV3 in both tadpole species and cattle land-use types; however, prevalence of FV3 was greater in green frog tadpoles residing in cattle-access wetlands compared to those in non-access wetlands. No difference in FV3 prevalence was detected between cattle land uses for American bullfrog tadpoles. A seasonal trend in FV3 prevalence also existed, with prevalence greater in autumn and winter than in summer for both species. In addition, we found that FV3 prevalence decreased significantly as Gosner stage increased in American bullfrog tadpoles. No trend was detected between FV3 prevalence and developmental stage for green frog tadpoles. Our results suggest that cattle use of wetlands may increase prevalence of FV3 in Rana tadpoles, although this effect may depend on species, season, and tadpole developmental stage.
蛙病毒已与美国大多数已报道的蛙类幼体死亡事件相关联。据推测，人为诱导的压力可能会通过损害免疫力来增加两栖动物种群中病原体的流行率。牛群对湿地的使用可能会因水质下降而给当地蝌蚪种群带来压力。我们从美国田纳西州坎伯兰高原的5个有牛群进入的湿地和3个无牛群进入的湿地采集的绿蛙（n = 80）和美国牛蛙（n = 104）蝌蚪中分离出一种蛙病毒。测序证实为蛙病毒3（FV3）；因此，我们比较了居住在有牛群进入和无牛群进入湿地的蝌蚪种群之间以及2005年三个季节（冬季、夏季和秋季）的FV3流行率。我们在两种蝌蚪物种和两种牛群使用类型的土地上都发现了FV3；然而，与无牛群进入湿地的绿蛙蝌蚪相比，居住在有牛群进入湿地的绿蛙蝌蚪中FV3的流行率更高。对于美国牛蛙蝌蚪，在两种牛群使用类型的土地上未检测到FV3流行率的差异。FV3流行率也存在季节性趋势，两种物种在秋季和冬季的流行率均高于夏季。此外，我们发现美国牛蛙蝌蚪中FV3流行率随着戈斯纳发育阶段的增加而显著下降。对于绿蛙蝌蚪，未检测到FV3流行率与发育阶段之间的趋势。我们的结果表明，牛群对湿地的使用可能会增加蛙属蝌蚪中FV3的流行率，尽管这种影响可能取决于物种、季节和蝌蚪发育阶段。
