title: Association between the existence of calves persistently infected with bovine viral diarrhea virus and commingling on pen morbidity in feedlot cattle.
abstract: OBJECTIVE
  To determine the association between the existence of a calf persistently infected (PI) with bovine viral diarrhea virus (BVDV) and pen morbidity.
  
  
  METHODS
  5,041 calves in 50 pens at a feedlot in Iowa.
  
  
  METHODS
  In a longitudinal study, ear notches were collected from cattle and tested for BVDV antigen. Characteristics of each pen (owner, sex, disease rate, number of groups, and source) were recorded. The association between the existence of a BVDV-PI calf and morbidity in each pen was examined.
  
  
  RESULTS
  Commingling was associated with an increase in respiratory tract disease (odds ratio [OR], 3; 95% confidence interval [CI], 2.5 to 3.6). Ten BVDV-PI calves (10/5,041 [0.2%]) were identified in 8 of 50 pens. A BVDV-PI calf was associated with reduced pen-level respiratory tract disease (OR, 0.7; 95% CI, 0.5 to 0.9). Disease prevalence (mean +/- SD morbidity, 7.9 +/- 3.1%) was lowest in pens containing single-source cattle and a BVDV-PI calf (4 pens containing 302 cattle), compared with single-source cattle with no BVDV-PI calf (mean morbidity, 11.89 +/- 9.7%; 31 pens containing 3,093 cattle), commingled cattle with no BVDV-PI calf (mean morbidity, 29.3 +/- 16.22%; 11 pens containing 1,127 cattle), and commingled cattle with a BVDV-PI calf (mean morbidity, 28.6 +/- 10.1%; 4 pens containing 519 cattle).
  
  
  CONCLUSIONS
  Commingling was the greatest risk factor associated with morbidity in each pen. A BVDV-PI calf in a pen was not associated with increased disease prevalence in commingled groups.
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011, USA.
authors.forename: Annette M
authors.initials: AM
authors.lastname: O'Connor
authors.forename: Steven D
authors.initials: SD
authors.lastname: Sorden
authors.forename: Michael D
authors.initials: MD
authors.lastname: Apley
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000453:epidemiology / Q000635:transmission*; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D001908:Diarrhea Viruses, Bovine Viral / Q000302:isolation & purification / Q000472:pathogenicity*; D004431:Ear, External / Q000821:virology; D006799:Housing, Animal; D007150:Immunohistochemistry / Q000662:veterinary; D007484:Iowa / Q000453:epidemiology; D016015:Logistic Models; D008137:Longitudinal Studies; D009017:Morbidity; D012140:Respiratory Tract Diseases / Q000517:prevention & control / Q000662:veterinary*