Center for Wildlife Health, Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, TN, USA.
Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool, UK.
Transbound Emerg Dis. 2022 Mar;69(2):731-741. doi: 10.1111/tbed.14043. Epub 2021 Mar 9.
Transmission is the fundamental process whereby pathogens infect their hosts and spread through populations, and can be characterized using mathematical functions. The functional form of transmission for emerging pathogens can determine pathogen impacts on host populations and can inform the efficacy of disease management strategies. By directly measuring transmission between infected and susceptible adult eastern newts (Notophthalmus viridescens) in aquatic mesocosms, we identified the most plausible transmission function for the emerging amphibian fungal pathogen Batrachochytrium salamandrivorans (Bsal). Although we considered a range of possible transmission functions, we found that Bsal transmission was best explained by pure frequency dependence. We observed that >90% of susceptible newts became infected within 17 days post-exposure to an infected newt across a range of host densities and initial infection prevalence treatments. Under these conditions, we estimated R = 4.9 for Bsal in an eastern newt population. Our results suggest that Bsal has the capability of driving eastern newt populations to extinction and that managing host density may not be an effective management strategy. Intervention strategies that prevent Bsal introduction or increase host resistance or tolerance to infection may be more effective. Our results add to the growing empirical evidence that transmission of wildlife pathogens can saturate and be functionally frequency-dependent.
传播是病原体感染宿主并在种群中传播的基本过程，可以用数学函数来描述。新兴病原体的传播功能形式可以决定病原体对宿主种群的影响，并为疾病管理策略的效果提供信息。通过在水生中观系统中直接测量受感染和易感成年东方蝾螈（Notophthalmus viridescens）之间的传播，我们确定了新兴两栖真菌病原体 Batrachochytrium salamandrivorans（Bsal）最合理的传播功能。尽管我们考虑了一系列可能的传播功能，但我们发现 Bsal 的传播最好由纯频率依赖性来解释。我们观察到，在一系列宿主密度和初始感染流行率处理下，超过 90%的易感蝾螈在接触受感染蝾螈后的 17 天内被感染。在这些条件下，我们估计 Bsal 在东方蝾螈种群中的 R 值为 4.9。我们的结果表明，Bsal 有能力使东方蝾螈种群灭绝，而管理宿主密度可能不是一种有效的管理策略。防止 Bsal 引入或增加宿主对感染的抵抗力或耐受性的干预策略可能更有效。我们的结果增加了越来越多的经验证据，即野生动物病原体的传播可以饱和并具有功能上的频率依赖性。
