Maguire Chelsea, DiRenzo Graziella V, Tunstall Tate S, Muletz Carly R, Zamudio Kelly R, Lips Karen R
Department of Integrative Biology, University of Illinois, Urbana-Champaign, IL 61820, USA.
Dis Aquat Organ. 2016 May 26;119(3):179-87. doi: 10.3354/dao02991.
Pathogens vary in virulence and rates of transmission because of many differences in the host, the pathogen, and their environment. The amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), affects amphibian hosts differently, causing extinction and population declines in some species but having limited effects on others. Phenotypic differences in zoospore production rates among Bd lineages likely contribute to some of the variation observed among host responses, although no studies have quantified the viability of zoospores shed from live animals. We compared host survivorship, infection intensity, shedding rates, and zoospore viability between 2 species of endangered tropical frogs, Hylomantis lemur and Atelopus zeteki, when exposed to a highly virulent lineage of Bd (JEL 423). We applied a dye to zoospores 30 to 60 min following animal soaks, to estimate shedding rate and proportion of live zoospores shed by different species. The average infection intensity for A. zeteki was nearly 17 times higher (31,455 ± 10,103 zoospore genomic equivalents [ZGEs]) than that of H. lemur (1832 ± 1086 ZGEs), and A. zeteki died earlier than H. lemur. The proportion of viable zoospores was ~80% in both species throughout the experiment, although A. zeteki produced many more zoospores, suggesting it may play a disproportionate role in spreading disease in communities where it occurs, because the large number of viable zoospores they produce might increase infection in other species where they are reintroduced.
由于宿主、病原体及其环境存在诸多差异，病原体的毒力和传播速率各不相同。两栖类壶菌，即蛙壶菌（Batrachochytrium dendrobatidis，简称Bd），对两栖类宿主的影响各异，导致一些物种灭绝和种群数量下降，而对其他物种影响有限。尽管尚无研究对活体动物释放的游动孢子的活力进行量化，但Bd谱系间游动孢子产生速率的表型差异可能是宿主反应差异的部分原因。我们比较了两种濒危热带蛙类，即马达加斯加树蛙（Hylomantis lemur）和巴拿马金蛙（Atelopus zeteki）在接触高毒力Bd谱系（JEL 423）时的宿主存活率、感染强度、释放速率和游动孢子活力。在动物浸泡后30至60分钟，我们对游动孢子进行染色，以估计不同物种释放的游动孢子的释放速率和活游动孢子比例。巴拿马金蛙的平均感染强度（31,455 ± 10,103个游动孢子基因组当量[ZGEs]）比马达加斯加树蛙（1832 ± 1086个ZGEs）高出近17倍，且巴拿马金蛙比马达加斯加树蛙更早死亡。在整个实验过程中，两种蛙类的活游动孢子比例均约为80%，尽管巴拿马金蛙产生的游动孢子更多，这表明在其所在的群落中，它在疾病传播中可能发挥着不成比例的作用，因为它们产生的大量活游动孢子可能会增加在其他物种中重新引入时的感染几率。
