Date of this Version
Published in Beef Research Program Progress Report, No. 4, Part 2 (May 1993)
Two main biotypes of bovine viral diarrhea virus (BVDV) have been identified based on their ability to cause changes in tissue culture cells. The cytopathic biotype multiplies in tissue culture and kills cells, while the noncytopathic biotype slowly multiplies in tissue culture and has much less ability to kill tissue culture cells. In general, cytopathic BVDV biotypes cause acute infections that often kill the bovine fetus, while noncytopathic BVDV biotypes often result in chronic infection of the fetus which, subsequently, develops in calves and adults that carry and shed noncytopathic viruses at high levels for the rest of their lives. Previous studies have indicated that cytopathic and noncytopathic viruses are antigenically similar. Also, after vaccination of cattle with modified-live or killed BVDV vaccines, antibodies are induced that neutralize a broad range of BVDV. However, very significant antigenic diversity among BVDV has been described. Also, studies indicated that some neutralizing antibodies from cattle that have recovered from BVDV react differently with several BVD isolates. In addition, monoclonal antibodies developed against specific BVDV isolates can differentiate BVDV into several groups and, when cattle which are persistently infected with noncytopathic BVDV are challenged with cytopathic BVDV, the antibodies they produce have a very narrow range of viral neutralizing activity. Thus, some antigenic diversity among BVDV, as detected by neutralization tests, is well established. However, there is little information that shows the practical consequences of this antigenic diversity relative to the disease in cattle. The primary purpose of this study was to identify cattle in U.S. Meat Animal Research Center's herd that were persistently infected with BVDV and test the isolates of BVDV from the U.S. Meat Animal Research Center herd to determine if these natural field viruses could be neutralized by serum obtained from U.S. Meat Animal Research Center cows vaccinated with killed BVDV.