Submitted to: Canadian Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2002
Publication Date: 7/24/2002
Citation: Fulton, R.W., Ridpath, J.F., Saliki, J.T., Briggs, R.E., Confer, A.W., Burge, L.J., Purdy, C.W., Loan, R.W., Duff, G.C. 2002. Bovine viral diarrhea virus (bvdv) 1b: predominant bvdv subtype in calves with respiratory disease.Canadian Journal of Veterinary Research. 66(3):181-190.
Interpretive Summary: Bovine viral diarrhea virus (BVDV) disease associated with acute bovine respiratory disease (a very complex disease involving many viruses, bacteria, and marketing stress) remains and enigma because various serotypes are found and their importance remains unknown. Both cytopathic and noncytopathic (don't produce cell destruction when isolated on tissue culture) forms occur. This virus also has the ability to immunosuppres the immune system of a young fetus if the virus invades through the placenta, after which the calf maybe unable to produce antibodies against the virus. In this case a persistent viremia occurs which can be a source of infection to other penmates. This virus has the ability to induce many different types of disease manifestations. All of these factors make this virus a complex one to understand. This research adds information over 2 years, concerning the virus serotype induction of disease under marketing stress conditions which befalls all feeder calves. The predominant viruses found were noncytopathic and the predominant subtype virus was BVDV1a. A noncytopathtic BVDV1b was detected in numerous samples from 1 persistently infected calf which did not seroconvert to BVDV1a or BVDV2. In both studies BVDV was isolated from serum, white blood cells, and nasal swabs, and in 1 study from the lung tissues. The BVDV was isolated more often from sick calves than healthy calves. This research indicates that BVDV1 strains are involved in acute respiratory disease of calves with bacteria. The isolation of BVDV1b could indicate that vaccines made with BVDV1a may not protect calves against BVDV1b.
Technical Abstract: The prevalence of bovine viral diarrhea virus (BVDV) infections was determined in 2 groups of stocker calves with acute respiratory disease. Both studies used calves assembled after purchase from auction markets by an order buyer and transported to feedyards, where they were held for approximately 30 d. During the studies, at day 0 and at weekly intervals, blood was collected for viral antibody testing and virus isolation from peripheral blood leukocytes (PBLs), and nasal swabs were taken for virus isolation. Samples from sick calves were also collected. Serum was tested for antibodies to bovine herpesvirus-1 (BHV-1), BVDV1a, 1b, and 2, parainfluenza 3 virus (PI3V), and bovine respiratory syncytial virus (BRSV). The lungs from the calves that died during the studies were examined histopathologically, and viral and bacterial isolation was performed on lung homogenates. BVDV was isolated from calves in both studies; the predominant biotype was noncytopathic (NCP) andthe predominant subtype was BVDV1b in both studies. NCP BVDV1b was detected in numerous samples over time from 1 persistently infected calf; the calf did not seroconvert to BVDV1a or BVDV2. In both studies, BVDV was isolated from the serum, PBLs, and nasal swabs of the calves, and in one study, it was isolated from lung tissue. BVDV was demonstrated serologically and by virus isolation to be a contributing factor in respiratory disease. It was isolated more frequently from sick calves than healthy calves. This study indicates that BVDV1 strains are involved in acute respiratory disease of calves with pneumonic Mannheimia haemolytica and Pasteurella multocida disease. The BVDV2 antibodies may be due to cross-reactions, as typing of the BVDV strains revealed BVDV1b or la but not BVDV2. The BVDV1b subtype has considerable implications, as, with 1 exception, all vaccines licensed in the United States contain BVDV1a, a strain with different antigenic properties. BVDV1b potentially could infect BVDV1a-vaccinated calves.