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Abstract：
Early and accurate detection of Mycoplasma hyopneumoniae infection in live pigs is a critical component to measure the success of disease eradication strategies. However, the imperfect sensitivity of in vivo diagnostic tools, change in sensitivity over the course of infection, and expected low prevalence level at the end of an eradication program create a challenging diagnostic scenario. Here, the individual and pool sensitivities for detection of M. hyopneumoniae during the chronic phase of infection was determined using deep tracheal catheter samples, the in vivo sample type with the highest reported diagnostic sensitivity. Fifty samples from known infected pigs collected at 113 days post-M. hyopneumoniae intra-tracheal inoculation, were diluted in known negative samples to form pools of 1:3 and 1:5. Samples were tested for M. hyopneumoniae by a species-specific PCR. Ninety-eight percent (49/50) of individual samples, 84 % (42/50) of pools of 1:3, and 82 % (41/50) of 1:5 were detected positive for M. hyopneumoniae. To apply the sensitivity estimates for detection of M. hyopneumoniae in a low prevalence scenario, sample sizes with associated sample collection costs were calculated for individual and pooled testing using algorithms within the program EpiTools One-Stage Freedom Analyses. Assumptions included a ≥95 % population sensitivity, infinite population size, prevalence levels of ≥0.5 %, ≥1 %, ≥2 %, ≥3 %, ≥4 %, or ≥5 %, 100 % specificity, along with the mean and lower confidence limit of the individual or pool sensitivity for each pool size, when appropriate. For instance, following completion of a herd eradication program, if a low risk approach is targeted, sample size estimates for ≥2 % prevalence using the lower limit of the diagnostic or pool sensitivity 95 %CI may be followed. If samples were to be tested individually, 167 individuals would be sampled at a cost of 6,012 USD. If pooled by 3, 213 would be sampled (testing cost 3,266 USD), and for pools of 5, 220 individuals would be sampled (testing cost 2,464 USD). Population sensitivity was also calculated for a range of testing scenarios. Our study indicated that pooling samples by 3 or 5 was a cost-effective method for M. hyopneumoniae detection in low prevalence scenarios. Cost-effective detection was evidenced despite the increased sample collection costs associated with large sample sizes in order to offset decreased testing sensitivity attributable to pooling. The post-eradication sample collection scheme, combined with pooling, suggested lower cost options than individual sampling for testing to be applied at the end of an eradication program, without significantly compromising the likelihood of detection.
摘要：
早期准确检测猪肺炎支原体感染是衡量疾病根除策略成功与否的关键要素。然而,体内诊断工具的灵敏度不完美，在感染过程中敏感性的变化，根除计划结束时预期的低患病率水平会产生具有挑战性的诊断方案。这里,使用深气管导管样本确定感染慢性期猪肺炎支原体的个体和池敏感性，报告的诊断灵敏度最高的体内样本类型。在M后113天收集的来自已知感染猪的50个样品。气管内接种猪肺炎,在已知的阴性样品中稀释以形成1:3和1:5的池。通过物种特异性PCR测试样品的猪肺炎支原体。百分之九十八（49/50）的单个样本，检测到猪肺炎支原体阳性的1：3的池的84％（42/50）和1：5的82％（41/50）。为了在低流行情况下检测猪肺炎支原体的敏感性估计，使用EpiTools一阶段自由分析程序中的算法,计算个体和合并测试的样本量及相关样本收集成本.假设包括≥95%的人群敏感度，无限的人口规模，患病率水平≥0.5%，≥1%,≥2%,≥3%,≥4%,或≥5%，100%特异性,以及每个池大小的个体或池灵敏度的平均和置信下限，在适当的时候。例如,在完成牛群根除计划后，如果以低风险方法为目标，使用95CI的诊断或池敏感性下限,对≥2%的患病率进行样本量估计.如果样品要单独测试，167个人将被抽样，费用为6,012美元。如果合并3,213将被抽样(测试成本为3,266美元)，对于5，220个人将被抽样(测试费用为2，464美元)。还计算了一系列测试方案的人口敏感性。我们的研究表明，在低流行情况下，将样本合并3或5是一种经济有效的猪肺炎支原体检测方法。尽管与大样本量相关的样品收集成本增加，以抵消由于合并而降低的测试灵敏度，但仍证明了具有成本效益的检测。根除后样本收集计划，结合池化，建议在根除计划结束时采用比单独取样更低的成本选项进行测试，而不会显著影响检测的可能性。
