Elnekave E, Shilo H, Gelman B, Klement E
Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel.
Kimron Veterinary Institute, The Foot and Mouth Disease laboratory, Beit Dagan, Israel.
Vet Microbiol. 2015 Jul 9;178(1-2):14-8. doi: 10.1016/j.vetmic.2015.04.003. Epub 2015 Apr 14.
ELISA tests for detection of anti NSP antibodies are extensively used in surveys estimating exposure of livestock to foot and mouth disease virus as a part of endemic and post epidemic surveillance programs. Yet, estimation of the longevity of anti NSP antibodies in naturally infected cattle and the sensitivity of ELISA tests based on them were rarely studied to date. Our research aim was to estimate the long term (up to 1118 days after exposure) change in levels of anti NSP antibodies in dairy cattle individuals naturally infected by FMDV and to evaluate the sensitivity of a commercially available ELISA kit in detecting anti NSP antibodies during the follow up period. A 3ABC blocking ELISA kit (PrioCHECK(®) FMDV NS) was used in a 3 years follow up study of repeatedly vaccinated cattle, which were found to be NSP positive during an FMD outbreak in a dairy farm. In order to rule out the possibility of a recurrent FMD outbreak involving the study population we combined clinical and laboratory monitoring: Cattle which were located in the same herd and were previously found as negative to anti NSP antibodies were followed and did not present FMD symptoms or a serological conversion. The overall sensitivity for infection detection was calculated using two approaches. When a conservative approach was taken and equivocal results (45%≤PI≤55%) were treated as negative, the sensitivities were 95% (CI95%=75.1-99.9%), 88.2% (CI95%=63.6-98.5%) and 76.9% (CI95%=46.2-95%) 311, 689 and 1118 days after the outbreak, respectively. However, when equivocal results were treated as positive, the sensitivities were 100% (CI95%=83.2-100%), 94.1% (CI95%=71.3-99.9%) and 92.3% (CI95%=64-99.8%) 311, 689 and 1118 days after the outbreak, respectively. We therefore conclude that this test can serve as a valuable tool for detection of previous FMDV infection in cattle in endemic countries, where routine vaccinations are implied, even several years after exposure.
用于检测抗NSP抗体的ELISA检测方法在估计家畜口蹄疫病毒暴露情况的调查中被广泛应用，作为地方病和疫情后监测项目的一部分。然而，迄今为止，对自然感染牛体内抗NSP抗体的持久性以及基于这些抗体的ELISA检测方法的敏感性研究甚少。我们的研究目的是估计自然感染口蹄疫病毒的奶牛个体中抗NSP抗体水平的长期变化（暴露后长达1118天），并评估一种市售ELISA试剂盒在随访期间检测抗NSP抗体的敏感性。在一项对反复接种疫苗的奶牛进行的为期3年的随访研究中，使用了一种3ABC阻断ELISA试剂盒（PrioCHECK(®) FMDV NS），这些奶牛在一个奶牛场的口蹄疫疫情期间被发现NSP呈阳性。为了排除涉及研究群体的口蹄疫疫情复发的可能性，我们结合了临床和实验室监测：对位于同一牛群且先前抗NSP抗体检测为阴性的奶牛进行跟踪，这些奶牛未出现口蹄疫症状或血清学转化。使用两种方法计算感染检测的总体敏感性。当采用保守方法，将可疑结果（45%≤PI≤55%）视为阴性时，疫情爆发后311天、689天和1118天的敏感性分别为95%（CI95%=75.1-99.9%）、88.2%（CI95%=63.6-98.5%）和76.9%（CI95%=46.2-95%）。然而，当将可疑结果视为阳性时，疫情爆发后311天、689天和1118天的敏感性分别为100%（CI95%=83.2-100%）、94.1%（CI95%=71.3-99.9%）和92.3%（CI95%=64-99.8%）。因此，我们得出结论，在实施常规疫苗接种的地方病流行国家，即使在暴露数年之后，该检测方法也可作为检测牛先前口蹄疫病毒感染的有价值工具。
