When BVD infects an animal, what are the possible outcomes?
Here is where the story gets complicated. The outcome depends on the BVD biotype and the “resistance” of the cattle involved. In the simplest case, if the cattle are adult, non-pregnant cattle and have been vaccinated against the infecting biotype previouslynothing happens. No disease, no death loss, nothing more than if they received a vaccine booster. Also, the age of the cattle is important, particularly the age of the fetus. If the fetus is exposed to a non-CPE BVD virus prior to day 120 of gestation it is possible the calf born will be an immunotolerant carrier of the virus. That is to say, the fetus may not be killed by the virus (aborted), will not mount an immune response to the virus, will shed large numbers of the non-CPE virus into the environment for as long as it lives. These immunotolerant carriers are called persistently infected (PI) cattle and usually live less than one year before dying. They are not only immunotolerant to the BVD virus, their immune system is permane
