BVD infection results in a wide variety of clinical signs, due to
its immunosuppressive effects, as well as having a direct effect on
respiratory disease and fertility.
Following viral entry and contact with the mucosal lining of the
mouth or nose, replication occurs in epithelial cells. BVDV
replication has a predilection for the palatine tonsils, lymphoid
tissues and epithelium of the oropharynx.
Phagocytes take up BVDV or virus-infected cells and transport them
to peripheral lymphoid tissues; the virus can also spread
systemically through the bloodstream. Viraemia occurs 2-4 days
after exposure and virus isolation from serum or leukocytes is
generally possible between 3-10 days post infection
During systemic spread the virus is able to gain entry into most
tissues with a preference for lymphoid tissues. Neutralising
antibodies can be detected from 10-14 days post infection with
titres continuing to increase slowly for 8-10 weeks. After 2-3
weeks, antibodies effectively neutralise viral particles, promote
clearance of virus and prevent seeding of target organs
|