Düngelhoef A, Lösken S, Grosse Beilage E
Prof. Dr. Elisabeth grosse Beilage, University of Veterinary Medicine Hannover, Field Station for Epidemiology, Buescheler Strasse 9, 49456 Bakum, Germany, Email:
Tierarztl Prax Ausg G Grosstiere Nutztiere. 2014;42(2):95-9.
Serological testing of blood samples is commonly known as an approved method to diagnose infectious diseases. Likewise it is used for monitoring infectious diseases as it is fast and cost-effective. Nevertheless interpretation of results can be difficult, especially when the samples were taken from animals, which received a vaccination prior to the serological examination. This is mainly due to the fact, that not every vaccination induces a measurable antibody reaction. In this recent case gilts were vaccinated with an attenuated live vaccine and the serum samples were negative in the ELISA. The question aroused which serological reaction to a vaccine is expected under field conditions.
In order to clarify this question a group of 28 gilts negative for porcine reproductive and respiratory syndrome (PRRS) virus (from a verifiable PRRSV-negative stock) were vaccinated with an attenuated PRRSV vaccine and blood samples were taken on days 0, 2, 4, 8 and 15 post vaccinationem (p. vacc). To provide a reliable means of diagnosis the samples were tested with an antibody ELISA and RT-PCR.
A replication of the vaccine virus was demonstrated via RT-PCR in 100% of the animals 4 days p. vacc. The first samples classified positive in the ELISA were detected 8 days p. vacc. On day 15 p. vacc. a positive serological result was obtained for all animals.
The vaccination with an attenuated PRRSV vaccine provides a pronounced antibody reaction under field conditions. In case of a negative serological reaction in recently vaccinated pigs all steps from the manufacturing process through to the implementation of the vaccine have to be critically evaluated. Likewise correct laboratory studies and the assessment of diagnostic results need to be scrutinized.
血液样本的血清学检测是诊断传染病的一种常用认可方法。同样，由于其快速且经济高效，也用于监测传染病。然而，结果的解读可能会很困难，尤其是当样本取自血清学检查前已接种疫苗的动物时。这主要是因为并非每种疫苗接种都会引发可测量的抗体反应。在最近这个案例中，后备母猪接种了减毒活疫苗，而ELISA检测血清样本呈阴性。于是产生了一个问题，即在现场条件下对疫苗预期会出现哪种血清学反应。
为了阐明这个问题，选取一组28头猪繁殖与呼吸综合征（PRRS）病毒阴性的后备母猪（来自可验证的PRRSV阴性种群），用减毒PRRSV疫苗进行接种，并在接种后第0、2、4、8和15天采集血样。为提供可靠的诊断方法，对样本进行抗体ELISA检测和RT-PCR检测。
通过RT-PCR在接种后4天的所有动物中均证实疫苗病毒发生了复制。ELISA检测中首次检测到阳性的样本是在接种后8天。接种后第15天，所有动物血清学结果均为阳性。
在现场条件下，接种减毒PRRSV疫苗会引发明显的抗体反应。如果最近接种疫苗的猪血清学反应呈阴性，则必须对从疫苗生产过程到疫苗接种实施的所有环节进行严格评估。同样，正确的实验室研究和诊断结果的评估也需要仔细审查。
