Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, 1365 Gortner Ave, St. Paul, MN, 55108, USA; Boehringer Ingelheim Animal Health USA Inc., 3239 Satellite Blvd NW, Duluth, GA, 30096, USA.
School of Public Health, Division Environmental Health Sciences, University of Minnesota, 1260 Mayo Building, 420 Delaware Street SE, Minneapolis, MN, 55454, USA.
Prev Vet Med. 2021 Apr;189:105313. doi: 10.1016/j.prevetmed.2021.105313. Epub 2021 Feb 24.
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.
早期和准确地检测活猪中的支原体感染是衡量疾病根除策略成功的关键组成部分。然而，体内诊断工具的不完美敏感性、感染过程中敏感性的变化以及根除计划结束时预期的低流行水平，创造了一个具有挑战性的诊断情况。在这里，使用深气管导管样本（报道的具有最高诊断敏感性的体内样本类型）确定了在感染的慢性阶段检测支原体感染的个体和池的敏感性。从感染支原体后 113 天采集的已知感染猪的 50 个样本，在已知的阴性样本中稀释，形成 1:3 和 1:5 的池。通过种特异性 PCR 测试支原体。98%（50/50）的个体样本、84%（42/50）的 1:3 池和 82%（41/50）的 1:5 池检测到支原体阳性。为了在低流行情况下应用检测支原体的敏感性估计，使用程序 EpiTools One-Stage Freedom Analyses 中的算法计算了个体和池检测的样本量以及相关的样本采集成本。假设包括≥95%的人群敏感性、无限的人群大小、≥0.5%、≥1%、≥2%、≥3%、≥4%或≥5%的流行水平、100%的特异性，以及个体或池敏感性的平均值和下限，适当时。例如，在完成畜群根除计划后，如果目标是低风险方法，可以遵循使用诊断或池敏感性 95%CI 的下限的≥2%流行率的样本量估计。如果要单独测试样本，将对 167 头个体进行采样，成本为 6012 美元。如果按 3 个进行分组，将对 213 个个体进行采样（测试成本 3266 美元），对于 5 个分组，将对 220 个个体进行采样（测试成本 2464 美元）。还计算了一系列检测方案的人群敏感性。我们的研究表明，在低流行率情况下，按 3 或 5 个分组对样本进行分组是一种经济有效的支原体检测方法。尽管与大样本量相关的样本采集成本增加，但仍然具有成本效益，因为这可以抵消由于分组而导致的检测敏感性降低。根除后样本采集方案与分组相结合，为根除计划结束时的检测提供了比单独采样更低成本的选择，而不会显著降低检测的可能性。
