Changes

BVDV isolates from either genotype can be of a cytopathic or non-cytopathic biotype. Noncytopathic (ncp) viruses produce no visible effects in cell culture, whereas infection with cytopathic (cp) viruses gives cell vacuolation and death. Although non-cytopathic isolates are responsible for the majority of BVDV infections worldwide, cytopathogenicity gives no indication of disease-causing potential. Cytopathic biotypes of bovine viral diarrhoea virus are always isolated alongside non-cytopathic strains, and are found in cases of mucosal disease, a fatal BVD-associated condition.  

BVDV isolates from either genotype can be of a cytopathic or non-cytopathic biotype. Noncytopathic (ncp) viruses produce no visible effects in cell culture, whereas infection with cytopathic (cp) viruses gives cell vacuolation and death. Although non-cytopathic isolates are responsible for the majority of BVDV infections worldwide, cytopathogenicity gives no indication of disease-causing potential. Cytopathic biotypes of bovine viral diarrhoea virus are always isolated alongside non-cytopathic strains, and are found in cases of mucosal disease, a fatal BVD-associated condition.  

Cytopathic viruses originate from non-cytopathic strains by mutation, including viral gene rearrangements, duplications and deletions¹⁷, and insertions of cellular origin, such as ubiquitin sequences. Point mutations in the NS2 region and various RNA recombination events are also important^?. Serologically, the two BVDV biotypes are indistinguishable, but on a molecular level cytopathic viruses produce an additional protein, NS3, not found in cells infected with non-cytopathic virus^{18, 19, 20}. This marker molecule arises from when NS2-3, expressed in non-cytopathic isolates, is cleaved at a site created by the mutations above²¹.

Cytopathic viruses originate from non-cytopathic strains by mutation, including viral gene rearrangements, duplications and deletions¹⁷, and insertions of cellular origin, such as ubiquitin sequences. Point mutations in the NS2 region and various RNA recombination events are also important¹⁸. Serologically, the two BVDV biotypes are indistinguishable, but on a molecular level cytopathic viruses produce an additional protein, NS3, not found in cells infected with non-cytopathic virus^{19, 20, 21}. This marker molecule arises from when NS2-3, expressed in non-cytopathic isolates, is cleaved at a site created by the mutations above²².

==Transmission and Epidemiology==

==Transmission and Epidemiology==