Do PI animals remain in herds for a long time?
Yes and No. Ninety percent of PI animals are culled from dairy herds before they reach 2 years of age but some PI animals can remain in the herd for several years. However, new PI animals are constantly developing as a result of fetal exposure to BVDV from PI animals. Remember that a persistently infected or PI animal is the only permanent carrier of BVD virus. Can I tell a PI animal by looking at it? Some PI animals are stunted and are poor doing but many appear normal and cannot be distinguished from non-PI animals. You must test an animal to determine if it is persistently infected with BVD virus. Can’t I control BVDV infection in my herd with a good strategic vaccination program? Yes and No. Vaccination usually protects animals from disease (illness and death) but does not protect them from becoming infected with the virus (subclinical infection). Subclinically infected animals can shed the virus in their blood (viremia) and hence expose the fetus to BVDV. How common are PI animals
