title: Antibody reaction in immunologically naïve replacement gilts vaccinated with an attenuated PRRSV live vaccine.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.forename: A
authors.initials: A
authors.lastname: Düngelhoef
authors.forename: S
authors.initials: S
authors.lastname: Lösken
authors.affiliation: Prof. Dr. Elisabeth grosse Beilage, University of Veterinary Medicine Hannover, Field Station for Epidemiology, Buescheler Strasse 9, 49456 Bakum, Germany, Email: elisabeth.grosse.beilage@tiho-hannover.de.
authors.forename: E
authors.initials: E
authors.lastname: Grosse Beilage
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology / Q000517:prevention & control; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology*; D016036:Seroepidemiologic Studies; D013552:Swine; D014765:Viral Vaccines / Q000008:administration & dosage* / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D014765:Viral Vaccines
keywords: ELISA; PRRSV; Pig; RT-PCR; vaccination