Bovine Viral Diarrhea Virus in Heterologous Hosts

Bovine viral diarrhea virus (BVDV) has been a virus of much interest for many decades. The implication of this thrifty virus impacts not only producers, but also veterinarians, researchers, and foreign animal disease diagnosticians. This session will touch on the history, epidemiology, and control of BVDV in cattle, with the primary emphasis on the role heterologous hosts play.
Bovine viral diarrhea virus, the prototypic pestivirus, was first identified in North America in 1946 in cattle, and less than a decade later in pigs in Europe. It is related to the Classical swine fever virus and Border disease virus of swine and small ruminants, respectively. Infection with BVDV causes gastrointestinal, respiratory and reproductive diseases, as well as immunosuppression. Immune suppression is the greatest economic impact felt by producers. The two main types of infection are acute or transient and persistent infections. Acute infections occur after birth when a naïve animal is exposed to the virus and disease develops. In contrast, persistent infections occur in-utero before the immune system of the fetus is competent, resulting in lifelong infection. As persistently infected animals shed virus from multiple body secretions more efficiently than any other mode of transmission, they are the most important source of maintenance of infection within a herd.
Natural infections occur in most species in the order Artiodactyla, including cattle, swine, sheep, goats, and camelids. Infections in heterologous (non-cattle) species also follow along the same lines as natural BVDV infections in cattle, including both transient acute infections and persistent infections. Prior research demonstrates that BVDV can circulate within heterologous host herds without the need for contact with cattle. In many types of farming practices, co-mingling of cattle with domestic small ruminants or swine are commonplace, increasing the risk of disease transmission between species. As many wild ruminants, cervids, and swine can also maintain the virus, the exposure of these animals to either domestic cattle or their environment pose a risk to the success of BVDV control programs. Classical swine fever is an important foreign animal disease, as it is antigenically related to BVDV, and both viruses can infect swine, therefore correct diagnosis and containment is crucial for protection of the pork industry. Understanding the role these heterologous hosts play in the maintenance and transmission of BVDV within these species will increase the success of BVDV control and eradication programs.