BVD virus: key characteristics

Volker Moennig

 

One of the key characteristics of the BVD virus is its’ structure; it is a small, enveloped virus which contains lipids and RNA. This combination makes it very susceptible to disinfectants and mild detergents. The BVD virus is closely related to other well-known diseases of veterinary importance such as Classical Swine Fever and Border Disease Virus of sheep. These three viruses are all members of the Pestivirus genus.

BVD is recognised to have two genotypes, or so-called species – BVDV 1 and BVDV 2. Within Europe, the most prevalent genotype is BVDV 1, with only up to 10 % BVDV 2 prevalence having been reported. Conversely in North America, BVDV 2 is widespread, with a 50:50 distribution.

With regard to their surface characteristics, BVD viruses are quite heterogeneous, so even among the respective genotypes there is variation. This is an important aspect to consider when it comes to vaccination. However, all BVD viruses are related and an antibody against one BVD virus will cross-neutralize other BVD viruses.

Another distinguishing feature of BVDV is the two biotypes; BVDV 1 and BVDV 2 naturally occur as the non-cytopathic biotype. In layman’s terms this means that when cell cultures in a laboratory are infected with the virus, the infection does not destroy the cells. Cytopathic biotypes, on the other hand, are mutations arising from non-cytopathic biotypes and will destroy the cells after infection. The distinction of biotypes plays an important role in understanding one facet of the disease – fatal mucosal disease.

The host spectrum of BVD is quite broad – apart from the obvious host, cattle, it can also infect sheep, goats, wild ruminants and even pigs. Since BVD is well adapted to the host species, it often does not trigger any clinical signs. Hence, farmers may not notice the introduction of BVD into their naïve herds. However this is not always the case, sometimes a highly virulent variant will enter the herd and cause considerable losses.