title: The diagnosis and prevalence of persistent infection with bovine viral diarrhoea virus in South African feedlot cattle.
abstract: Bovine viral diarrhoea virus (BVDV) infection is an important viral infection affecting the  cattle industry today. The prevalence of this infection in South African feedlots is unknown.  Ear notch biopsies were collected from chronic poor doers and animals that appeared  unthrifty upon entering feedlots, as well as animals entering the hospital pen with respiratory  disease for the first time. A total of 1690 samples were collected: 1074 from the former  category and 616 from the latter. A routine immunohistochemistry staining protocol showed  that 49 animals tested positive, of which 43 (4%) came from the feedlot entry group and six  (1%) from the hospitalised group. The prevalence of persistently infected cattle from this  selected, nonrandom sample entering six large South African feedlots was found to be 2.9%,  which is higher than the international rule of thumb that 0.5% of all cattle entering feedlots  are persistently infected. There was no clear correlation between persistent infection and  respiratory disease. Serum samples were also collected when possible and 10 positive cases  were found. Results from enzyme-linked immunosorbent assays for antigen and antibody  performed on these sera correlated well with those from the immunohistochemistry staining  method in six cases, but in four cases the animals tested falsely positive owing to nonspecific  staining. Immunohistochemistry staining on ear notch biopsies is thus a reliable diagnostic  method to identify persistently infected animals with BVDV, but the pathologist should be  aware of nonspecific positive staining.
authors: . thelma@idexxsa.co.za.
authors: Thelma
authors: T
authors: Meiring
authors: Leon
authors: L
authors: Prozesky
authors: Eben R
authors: ER
authors: Du Preez
authors: Dirk J
authors: DJ
authors: Verwoerd
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D000956:Antigens, Viral / Q000032:analysis; D001912:Bovine Virus Diarrhea-Mucosal Disease / Q000175:diagnosis* / Q000453:epidemiology*; D002417:Cattle; D001908:Diarrhea Viruses, Bovine Viral / Q000276:immunology / Q000302:isolation & purification; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005260:Female; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D015995:Prevalence; D013019:South Africa / Q000453:epidemiology
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral