Epidemiology Research Unit, Department of Veterinary and Animal Science, Northern Faculty, Scotland's Rural College (SRUC), An Lòchran, 10 Inverness Campus, Inverness, UK.
Pharmaq Analytiq, 22 Carsegate Road, Inverness, Scotland, UK.
Prev Vet Med. 2022 Jul;204:105654. doi: 10.1016/j.prevetmed.2022.105654. Epub 2022 Apr 22.
Amoebic gill disease (AGD) and complex gill disease (CGD) are the most significant marine gill diseases in salmon aquaculture in Scotland. Little is published about diagnostic performance of tests to detect these diseases, making it difficult to interpret test results. We estimated diagnostic sensitivity (DSe) and specificity (DSp) of common tests for AGD (gross AGD score, qPCR for Neoparamoeba perurans, histopathology) and CGD (gross proliferative gill disease (PGD) score, gross total gill score, histopathology). Because specifications in our sampling protocol implemented to encourage consistency across the farms might affect diagnostic performance of histopathology (historically the reference standard for gill diseases), we used Bayesian latent class models without reference standard. Cases and non-cases were based on less, medium, and severe stringent case definitions, representing different cut-off levels for the different tests. Gross gill scores for both diseases were excellent in designating non-diseased fish, DSps were generally around 1. To detect CGD, DSe of gross total gill score and gross PGD score were between respectively 0.81 (0.73 - 0.91 lower to upper 95% credible interval) and 0.53 (0.46 - 0.64) for medium stringent case definitions, and to detect AGD the DSe for the gross AGD score was between 0.53 (0.48-0.57) and 0.14 (0.07 - 0.22) for respectively the less and severe stringent case definition. Thus, gross gill scores were medium to good in designating truly diseased fish, implying some false negatives are expected. For CGD the DSe for gross total gill scores were the highest, for AGD it was the qPCR test at a DSe of 0.92 (0.86 - 0.99). For both diseases, DSe was lowest for histopathology, e.g. 0.23 (0.16 - 0.30) for AGD and 0.1 (0.07 - 0.14) for CGD under medium stringent case definitions, perhaps due to collecting the second gill arch on the right rather than the worst affected arch, whilst PCR sampling and gross gill scoring included multiple (PCR) or all (gross scoring) gill arches. The diagnostic goals of these tests differ; gross gill scoring provides a low-cost presumptive diagnosis, PCR a non-lethal confirmation of the presence of a specific pathogen and histopathology provides information on the underlying aetiology of gill damage as well as the extent, severity, and chronology of gill disease. An effective gill health surveillance strategy is likely to incorporate multiple diagnostic tools used in a complementary manner.
变形虫性鳃病（AGD）和复杂鳃病（CGD）是苏格兰鲑鱼养殖中最重要的海洋鳃病。关于检测这些疾病的测试的诊断性能发表的文章很少，因此难以解释测试结果。我们估计了常见的 AGD 检测方法（总鳃评分、Neoparamoeba perurans 的 qPCR、组织病理学）和 CGD 检测方法（总增殖性鳃病评分、总总鳃评分、组织病理学）的诊断敏感性（DSe）和特异性（DSp）。由于我们的采样方案中的规范旨在鼓励各个农场之间的一致性，这可能会影响组织病理学的诊断性能（历史上是鳃病的参考标准），因此我们使用了没有参考标准的贝叶斯潜在类别模型。病例和非病例是基于较严格、中等严格和严格严格的病例定义，代表不同测试的不同截止水平。两种疾病的总鳃评分在指定无病鱼方面表现出色，DSp 通常约为 1。为了检测 CGD，中等严格病例定义下，总总鳃评分和总增殖性鳃病评分的 DSe 分别为 0.81（0.73-0.91 的置信区间下 95%上限）和 0.53（0.46-0.64），而对于 AGD，DSe 对于总鳃评分分别为 0.53（0.48-0.57）和 0.14（0.07-0.22），用于分别是较严格和严格严格的病例定义。因此，总鳃评分在指定真正患病的鱼类方面表现中等至良好，这意味着可能会出现一些假阴性。对于 CGD，总总鳃评分的 DSe 最高，对于 AGD，qPCR 测试的 DSe 为 0.92（0.86-0.99）。对于这两种疾病，组织病理学的 DSe 最低，例如在中等严格的病例定义下，AGD 为 0.23（0.16-0.30），CGD 为 0.1（0.07-0.14），这可能是由于在右侧收集了第二鳃弓，而不是最受影响的弓，而 PCR 采样和总鳃评分包括多个（PCR）或所有（总评分）鳃弓。这些测试的诊断目标不同；总鳃评分提供了一种低成本的初步诊断，PCR 提供了对特定病原体存在的非致死性确认，而组织病理学提供了有关鳃损伤的潜在病因以及鳃病的程度、严重程度和时间进程的信息。一种有效的鳃健康监测策略可能是结合使用多种以互补方式使用的诊断工具。
