title: Comparative virulence of isolates of bovine viral diarrhea virus type II in experimentally inoculated six- to nine-month-old calves.
abstract: OBJECTIVE
  To determine the comparative virulence of 5 isolates of bovine viral diarrhea virus (BVDV) type II by inoculating 6- to 9-month-old beef calves with isolates originating from the tissues of cattle affected with naturally occurring, transient, acute, nonfatal infections or naturally occurring, peracute, fatal infections.
  
  
  METHODS
  22 calves that were 6 to 9 months old.
  
  
  METHODS
  The study used BVDV isolates 17011, 713, and 5521 that originated from fetuses aborted from cows with transient, nonfatal, acute BVDV infections and isolates 23025 and 17583 that originated from the tissues of cattle with peracute, fatal BVDV infections. Calves were allotted to 6 groups (1, mock-infected control calves [n = 2]; 2, inoculated with BVDV 17011 [4]; 3, inoculated with BVDV 713 [4]; 4, inoculated with BVDV 5521 [4]; 5, inoculated with BVDV 23025 [4]; and 6, inoculated with BVDV 17583 [41]. Rectal temperatures and clinical signs of disease were recorded daily. Total and differential WBC and platelet counts were performed. Histologic examination and immunohistochemical analysis were conducted to detect lesions and distribution of viral antigens, respectively.
  
  
  RESULTS
  Calves inoculated with BVDV 23025 or 17583 developed more severe clinical signs of disease (fever and diarrhea), more severe lymphopenia, and more severe lesions (alimentary epithelial necrosis, lymphoid depletion, and BVDV antigen deposition in lymphatic tissues), compared with calves inoculated with BVDV 713, 5521, or 17011.
  
  
  CONCLUSIONS
  Relative severity of experimentally induced infections corresponded to severity of clinical signs of naturally occurring infections with respective BVDV isolates.
authors.affiliation: Department of Veterinary and Biomedical Sciences, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln 68583-0905, USA.
authors.forename: Clayton L
authors.initials: CL
authors.lastname: Kelling
authors.forename: David J
authors.initials: DJ
authors.lastname: Steffen
authors.forename: Christina L
authors.initials: CL
authors.lastname: Topliff
authors.forename: Kent M
authors.initials: KM
authors.lastname: Eskridge
authors.forename: Ruben O
authors.initials: RO
authors.lastname: Donis
authors.forename: Deborrah S
authors.initials: DS
authors.lastname: Higuchi
mesh_terms: D000375:Aging; D000818:Animals; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000821:virology*; D002417:Cattle; D030242:Diarrhea Virus 2, Bovine Viral / Q000145:classification* / Q000472:pathogenicity*; D013997:Time Factors; D014774:Virulence