title: Descriptive epidemiology of postnatal bovine viral diarrhea virus infection in intensively managed dairy heifers.
abstract: OBJECTIVE
  To evaluate risk of bovine viral diarrhea virus (BVDV) infection between birth and 9 months of age for dairy replacement heifers raised under typical dry-lot management conditions.
  
  
  METHODS
  Longitudinal observational study.
  
  
  METHODS
  446 calves.
  
  
  METHODS
  Calves were randomly selected from 2 dairies that used killed and modified-live BVDV vaccines. Repeated serologic and BVDV polymerase chain reaction assays were used to estimate risk of BVDV infection in calves of various ages (1 to 60 days; 61 to 100 days; 101 days to 9 months) and to estimate overall infection rate by 9 months of age.
  
  
  RESULTS
  Risk of BVDV infection increased with age (maximum risk, 150 to 260 days). Proportion of calves infected with BVDV by 9 months of age was higher for dairy A (0.665), compared with dairy B (0.357). Percentage infected with BVDV type I did not differ between dairy A (18.2%) and dairy B (15.2%), whereas percentage infected with BVDV type II for dairy A (50%) was twice that for dairy B (21%). Between 210 and 220 days of age, infection with BVDV regardless of type was > 1.3%/d on dairy A and 0.5%/d on dairy B.
  
  
  CONCLUSIONS
  Under dry-lot conditions, a considerable amount of BVDV infection may occur before 9 months of age. Risk of infection increases with age. Although dairies may appear to have similar management practices, there can be considerably different risks of BVDV infection among dairies.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis 95616, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Rush
authors.forename: M C
authors.initials: MC
authors.lastname: Thurmond
authors.forename: C A
authors.initials: CA
authors.lastname: Muñoz-Zanzi
authors.forename: S K
authors.initials: SK
authors.lastname: Hietala
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000097:blood / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D002140:California / Q000453:epidemiology; D002417:Cattle; D003612:Dairying / Q000379:methods*; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology; D005260:Female; D008137:Longitudinal Studies; D012307:Risk Factors; D014611:Vaccination / Q000662:veterinary; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology
chemical_list: D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated; D014765:Viral Vaccines