Fish translocations are an important tool in fisheries management, yet translocating fish carries the risk of introducing unwanted pathogens. Although pathogen screening can be a useful tool for managing the risk associated with fish translocations, screening cannot eliminate this risk. This paper addresses these problems by demonstrating that two elements must be considered when designing efficient and effective aquatic pathogen screening programs: (1) how many fish to screen and (2) how long to continue screening programs when repeated testing detects zero infected individuals. The chance that infected fish are translocated despite screening is the joint probability of (1) the failure of the screening to detect infected fish in the sample and (2) the actual presence of infected fish in the translocation batch. Our analysis demonstrates that transfer of an infected fish is most likely to occur at moderately low levels of pathogen prevalence because the probability of detecting at least one infected fish through screening increases as pathogen prevalence increases. Small screening samples (i.e., with a low number of individuals) are most likely to detect infected fish when pathogen prevalence is relatively high (i.e., > 5%). Screening programs should terminate after some number of successive screening events in which no infected individuals have been detected. The number of screening events is a function of the cost of the screening program, the cost of a pathogen translocation, and the probability that an infected fish will be transferred. Furthermore, our analysis indicates that the cost of a disease outbreak has relatively little effect on the length of time the screening program should continue. A more pronounced result is that screening programs that are inexpensive or allow a higher probability of pathogen translocation should be continued longer.

中文翻译：

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鱼类病原体筛查及其对鱼类易地过程中意外病原体引入可能性的影响

鱼类易地是渔业管理的重要工具，但易地鱼类存在引入有害病原体的风险。尽管病原体筛查可以成为管理与鱼类易地相关的风险的有用工具，但筛查并不能消除这种风险。本文通过证明在设计高效和有效的水生病原体筛查计划时必须考虑两个要素来解决这些问题：(1) 要筛查多少鱼和 (2) 当重复检测检测到零感染个体时，继续筛查计划需要多长时间。尽管进行了筛查，受感染的鱼仍易位的可能性是以下联合概率：(1) 筛查未能检测到样本中的受感染鱼，以及 (2) 易位批次中实际存在受感染的鱼。我们的分析表明，受感染鱼类的转移最有可能发生在病原体流行程度中等偏低的情况下，因为随着病原体流行程度的增加，通过筛查检测到至少一种受感染鱼类的可能性也会增加。当病原体流行率相对较高（即 > 5%）时，小筛选样本（即个体数量少）最有可能检测到受感染的鱼。筛查计划应在一定数量的连续筛查事件之后终止，其中没有检测到感染者。筛查事件的数量是筛查计划成本、病原体易位成本和受感染鱼被转移的可能性的函数。此外，我们的分析表明，疾病爆发的成本对筛查计划应该持续的时间长度的影响相对较小。一个更显着的结果是，廉价的或允许病原体易位可能性更高的筛查计划应该持续更长时间。