Evaluation of diagnostic tests used for detection of bovine viral diarrhea virus and prevalence of subtypes 1a, 1b, and 2a in persistently infected cattle entering a feedlot.
OBJECTIVE
To evaluate diagnostic tests used for detection of bovine viral diarrhea virus (BVDV) and determine the prevalence of BVDV subtypes 1a, 1b, and 2a in persistently infected (PI) cattle entering a feedlot.


METHODS
Prospective study.


METHODS
21,743 calves.


METHODS
Samples were obtained from calves initially testing positive via antigen capture ELISA (ACE) performed on fresh skin (ear notch) specimens, and ACE was repeated. Additionally, immunohistochemistry (IHC) was performed on skin specimens fixed in neutral-buffered 10% formalin, and reverse transcriptase PCR (RT-PCR) assay and virus isolation were performed on serum samples. Virus was subtyped via sequencing of the 5' untranslated region of the viral genome.


RESULTS
Initial ACE results were positive for BVDV in 88 calves. After subsequent testing, results of ACE, IHC, RT-PCR assay, and viral isolation were positive in 86 of 88 calves; results of all subsequent tests were negative in 2 calves. Those 2 calves had false-positive test results. On the basis of IHC results, 86 of 21,743 calves were PI with BVDV, resulting in a prevalence of 0.4%. Distribution of BVDV subtypes was BVDV1b (77.9%), BVDV1a (11.6%), and BVDV2a (10.5%).


CONCLUSIONS
Rapid tests such as ACE permit identification and segregation of PI cattle pending results of further tests, thus reducing their contact with the rest of the feedlot population. Although vaccines with BVDV1a and 2a components are given to cattle entering feedlots, these vaccines may not provide adequate protection against BVDV1b.
Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078, USA.
Robert W
RW
Fulton
Bill
B
Hessman
Bill J
BJ
Johnson
Julia F
JF
Ridpath
Jeremiah T
JT
Saliki
Lurinda J
LJ
Burge
Dave
D
Sjeklocha
Anthony W
AW
Confer
Rebecca A
RA
Funk
Mark E
ME
Payton
D000818:Animals; D000956:Antigens, Viral / Q000032:analysis; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000097:blood / Q000175:diagnosis*; D002417:Cattle; D030241:Diarrhea Virus 1, Bovine Viral / Q000145:classification / Q000302:isolation & purification*; D030242:Diarrhea Virus 2, Bovine Viral / Q000145:classification / Q000302:isolation & purification*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary*; D007150:Immunohistochemistry / Q000379:methods / Q000662:veterinary*; D011446:Prospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary*; D012680:Sensitivity and Specificity
D000956:Antigens, Viral