Submitted to: Veterinary Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/15/2005
Publication Date: 5/31/2006
Citation: Ridpath, J.F., Neill, J.D., Vilcek, S., Dubovi, E.J., Carman, S. 2006. Multiple outbreaks of severe acute BVDV in North America occurring between 1993 and 1995 linked to the same BVDV2 strain. Veterinary Microbiology. 114(3-4):196-204. Interpretive Summary: Infections with bovine viral diarrhea (BVD) viruses (BVDV) are a source of major economic loss to U.S. cattle producers. Variation among BVDV strains impacts upon the study and control of BVD outbreaks. One variation observed among BVDV strains is the severity of the disease that follows infection. In other words, BVDV strains differ in virulence. In this study we found that several outbreaks of severe acute BVD observed between 1993 and 1995 in North America can be traced to a single strain of BVDV. Unlike most BVDV strains, which are low virulence, this strain which is high virulence, spread quickly from herd to herd and caused significant death losses. The explosive spread of this virus suggests that outbreaks of high virulence strains must be controlled differently than outbreaks of low virulence strains. This strain was isolated in several different laboratories in the United States and Canada and each laboratory gave the virus a different name. This can be a problem when researchers are doing studies to compare viruses and don’t realize that isolates with different names may actually be the same strain. Scientists need to come up with a system of naming viruses that clearly labels re isolations of the same strain. The impact of this report is that it identifies a single BVDV strain as the cause of a North American epidemic that previously was attributed to viruses of different names.
Technical Abstract: The first reported outbreak of bovine viral diarrhea (BVD) in 1946 described a transmissible acute disease characterized by severe leukopenia, high fever, gastrointestinal erosions and hemorrhages. However, in the ensuing years the most commonly observed acute form of BVD was clinically mild. There was limited viral shed and spread following these acute infections. This led to an assumption that acute infections with BVD viruses (BVDV) infection were clinically unimportant, spread of the within a group was always due to the presence of a persistently infected animal and transmission between healthy immunocompetent cattle was insignificant. The conventional wisdom was challenged when outbreaks of severe acute BVDV was observed in North America starting in the late 1980’s. This study demonstrates that several outbreaks of severe acute BVD observed in 1993 in North America can be traced to a single strain of BVDV that spread explosively following acute infection. These findings are notable in that they draw into question management of acute BVD infection, design of studies examining virulence and nomenclature used to identify strains for GenBank submission.