GD Animal Health Service Ltd, Arnsbergstraat 7, P.O. Box 9, 7400 AA Deventer, The Netherlands.
Vet Microbiol. 2011 May 12;150(1-2):180-4. doi: 10.1016/j.vetmic.2011.01.001. Epub 2011 Jan 11.
A cross-sectional study was conducted to find the most effective diagnostic approach to detect circulation of porcine reproductive and respiratory syndrome virus (PRRSV). The study was performed in 10 Dutch swine herds, with sows and fattening pigs or breeding stock. Herds did not experience clinical signs of PRRS during the last 6 months before sampling, but a PRRSV infection was confirmed at most 2 years before sampling. Blood samples were collected from 5 age groups: sows during early and late gestation, weaners at 9 weeks of age, fatteners or breeding stock at 16 and 22 weeks of age. For each category, 20 serum samples were examined; in total 100 serum samples per herd. Samples were analysed for PRRSV antibodies with ELISA (n=1002), and rt-PCR when ELISA S/P-ratios were above 1.5 (n=307) or below 0.4 (n=187; random selection from each age group). A logistic regression analysis was used to obtain factors associated with the probability of virus detection in a pig (PCR positive test result). Herd, ELISA-result, and age group were included as explanatory variables. Variables remained in the model when statistically significant. ELISA results showed that none of the herds could be considered to be free of PRRSV infection. Mean PRRSV seroprevalence in unvaccinated animals varied between 18% and 82%, and mean PRRS-virus prevalence varied between 0% and 41%. In only one of the 10 herds, no PRRS-virus could be detected. The odds of finding PRRS-virus in blood samples were 8.6 (95% CI, 5.3-13.9) in pigs of 9 weeks of age and 4.6 (95% CI, 3.0-7.0) in pigs of 16 weeks of age, compared with fatteners of 22 weeks of age. This result indicates that 9- to 16-week-old pigs are the preferred age group to detect PRRS-virus, in herds without clinical signs of PRRS. We concluded that PRRS-virus circulation could be detected in 8 out of 9 of the study-herds, with a relatively low number of blood samples. Testing 12 blood samples in both rt-PCR and ELISA, with 6 samples in pigs 9 weeks of age and 6 samples in pigs 16 weeks of age, will lead to a cost-efficient first evaluation of the PRRSV infection-status in herds without clinical signs of PRRS.
一项横断面研究旨在寻找最有效的诊断方法来检测猪繁殖与呼吸综合征病毒（PRRSV）的循环。该研究在 10 个荷兰猪场进行，涉及母猪和育肥猪或种猪。在采样前的最近 6 个月内，这些猪场没有出现 PRRS 的临床症状，但在采样前的 2 年内，已经确认存在 PRRSV 感染。从 5 个年龄组采集血液样本：妊娠早期和晚期的母猪、9 周龄断奶仔猪、16 周龄和 22 周龄的育肥猪或种猪。每个类别采集 20 份血清样本；每个猪场总共采集 100 份血清样本。使用 ELISA（n=1002）检测 PRRSV 抗体，当 ELISA S/P 比值高于 1.5（n=307）或低于 0.4（n=187；从每个年龄组随机选择）时，使用 rt-PCR 进行检测。使用逻辑回归分析获得与猪病毒检测概率相关的因素（PCR 阳性检测结果）。将猪场、ELISA 结果和年龄组作为解释变量。当统计上有意义时，变量保留在模型中。ELISA 结果表明，没有一个猪场可以被认为没有 PRRSV 感染。未接种疫苗动物的 PRRSV 血清阳性率在 18%至 82%之间，PRRS 病毒阳性率在 0%至 41%之间。在 10 个猪场中，只有一个猪场未检测到 PRRS 病毒。与 22 周龄育肥猪相比，9 周龄和 16 周龄猪血液样本中 PRRS 病毒的检出率分别为 8.6（95%CI，5.3-13.9）和 4.6（95%CI，3.0-7.0）。这一结果表明，在没有 PRRS 临床症状的猪场中，9 至 16 周龄的猪是检测 PRRS 病毒的首选年龄组。我们得出结论，在 9 个研究猪场中的 8 个猪场中可以检测到 PRRS 病毒循环，而且只需要相对较少的血液样本。在没有 PRRS 临床症状的猪场中，使用 rt-PCR 和 ELISA 对 12 份血液样本进行检测，其中 6 份样本来自 9 周龄的猪，6 份样本来自 16 周龄的猪，这将是一种具有成本效益的 PRRSV 感染状况的初步评估方法。
