Getting a handle on bovine viral diarrhea virus, especially persistent infections (PI), requires knowing how a PI calf is created.
A PI calf is the result of an in utero infection, says Bruce Brodersen, veterinarian with the University of Nebraska Veterinary Diagnostic Center.
This infection can occur in two ways. First and most common is when there is an acute or transient infection of the dam. That infection can be passed to the fetus.
“Cows not well-vaccinated have the greatest chance of creating PI calves when that infection takes place,” Brodersen says. “Many vaccines are labeled as offering fetal protection and that is the reason those vaccines were developed, to protect from PI calves being created.”
Second is when the dam is PI, she will always have a PI calf. “It is essential the dam and her calf can be identified as a pair, since the dam will need to be found after the results of the calf test are reported from the laboratory,” Brodersen advises.
Read more about testing for PI BVDV calves in Bovine Veterinarian here.