title: Serologic evaluation of five unvaccinated heifers to detect herds that have cattle persistently infected with bovine viral diarrhea virus.
abstract: OBJECTIVE
  To determine whether serologic evaluation of 5 unvaccinated 6- to 12-month-old heifers is a valid method for identifying herds that contain cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV).
  
  
  METHODS
  14 dairy herds with a history of BVDV infection, with health problems consistent with BVDV infection, or at risk for contracting BVDV infection.
  
  
  METHODS
  5 unvaccinated 6- to 12-month-old heifers were randomly selected from each herd. Neutralizing antibody titers for type-I and -II BVDV were determined. A herd was classified as likely to contain PI cattle when at least 3/5 heifers had antibody titers > or = 128. Virus isolation was performed on all cattle to identify PI cattle. Genotype of isolated viruses was determined by nested multiplex polymerase chain reaction.
  
  
  RESULTS
  6 of 14 herds contained PI cattle. Sensitivity and specificity of serologic evaluation of 5 heifers for identifying these herds were 66 and 100%, respectively. In herds that contained PI cattle, the predominant BVDV titer in the tested heifers corresponded to the genotype of the isolated virus.
  
  
  CONCLUSIONS
  Serologic evaluation of unvaccinated 6- to 12- month-old heifers is an accurate method for identifying herds containing PI cattle. Both type-I and -II BVDV antibody titers should be determined to prevent herd misclassification. The genotype of BVDV found in PI cattle can be predicted by the predominant neutralizing antibody titers found in tested heifers. Serologic evaluation of 5 unvaccinated heifers can be used to determine whether a herd is likely to contain PI cattle.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA.
authors.forename: Roxanne B
authors.initials: RB
authors.lastname: Pillars
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Grooms
mesh_terms: D000822:Animal Husbandry; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D002353:Carrier State / Q000662:veterinary* / Q000821:virology; D002417:Cattle; D001908:Diarrhea Viruses, Bovine Viral / Q000235:genetics / Q000302:isolation & purification*; D005260:Female; D008892:Milk / Q000821:virology; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D018401:Sample Size; D017422:Sequence Analysis, DNA; D016036:Seroepidemiologic Studies
chemical_list: D000914:Antibodies, Viral; D012367:RNA, Viral