VIOLIN: Vaccine Investigation and Online Information Network

I. General Information

1. NCBI Taxonomy ID:

2. Disease:

Bovine viral Diarrhea (BVD)

3. Introduction

Bovine viral diarrhea (BVD) is most common in young cattle (6-24 mo old) and generally is accompanied by typical mucosal lesions; it must be distinguished from other viral diseases that produce diarrhea and mucosal lesions. Bovine viral diarrhea virus (BVDV), the causal agent of BVD and mucosal disease complex, is classified in the genus Pestivirus in the family Flaviviridae. Although cattle are the primary host for BVDV, several reports suggest most even-toed ungulates are also susceptible. Isolates of BVDV are separated into noncytopathic and cytopathic biotypes based on cytopathic effects observed in infected cell cultures. Noncytopathic BVDV are the predominant viral biotype in nature. Cytopathic BVDV are relatively rare and arise in cattle that are persistently infected with noncytopathic BVDV. The switch in viral biotype is triggered by mutations that often involve recombination of noncytopathic viral RNA with itself, with heterologous viral RNA, or with host cell RNA. Based on viral RNA sequence, there are at least 2 viral genotypes of BVDV that can be further divided into subgenotypes. The viral genotypes are termed BVDV type 1 and BVDV type 2, and both cytopathic and noncytopathic BVDV are represented in each viral genotype. Although the viral genotypes are antigenically related, serologic assays can separate BVDV type 1 from BVDV type 2. Serologic surveys indicate that BVDV is distributed worldwide. The prevalence of antiviral antibody in cattle varies among countries and may vary between geographic regions within a country. Prevalence of antiviral antibody may be >90% if vaccination is practiced commonly in a geographic region. Although cattle of all ages are susceptible, most cases of overt clinical disease are seen in cattle that are between 6 mo and 2 yr of age. Cattle that are persistently infected with noncytopathic BVDV serve as a natural reservoir for virus. Persistent infection develops when noncytopathic BVDV is transmitted transplacentally during the first 4 mo of fetal development. The calf is born infected with virus, remains infected for life, and usually is immunotolerant to the resident noncytopathic virus. Transplacental infection that occurs later in gestation results in abortion, congenital malformations, or birth of normal calves that have antibody against BVDV. The prevalence of persistent infection varies among countries and between regions within a country. In some areas, the prevalence of persistent infection in calves may be as high as 1-2% of cattle <1 yr of age. On a given farm, persistently infected cattle are often found in cohorts of animals that are approximately the same age. Persistently infected cattle can shed large amounts of BVDV in their secretions and excretions and readily transmit virus to susceptible herdmates. Clinical disease and reproductive failure often are seen after healthy cattle come in contact with a persistently infected animal. Biting insects, fomites, semen, biologic products, and possibly wild ruminants also can spread BVDV (Merck Vet Manual: Bovine Viral Diarrhea).

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