The PI-3 virus is relatively common in cattle and is found worldwide. Affected animals exhibit watery to yellow-colored discharges from the eyes and nose, coughs, increased respiration rates and fever. By itself, PI-3 is a relatively mild infection; death loss to the disease is rare, maybe even nonexistent. However, it generally works in concert with IBR, BVD, BRSV, pasteurella pneumonia and Haemophilus somnus infections, making the mixed infections more damaging and dangerous. Because PI-3 can enhance the damage of the other diseases, PI-3 vaccines are almost always found combined with IBR, BVD and/or BRSV vaccines.
As with most diseases, calves are the most susceptible to PI-3; therefore, vaccination of cows to provide maternal antibodies to the newborn is recommended. In addition, calves should be properly vaccinated before weaning and/or shipment.
PI-3 vaccines are available in replicating, nonreplicating, and intranasal forms. All three forms are safe for use in any age cattle, regardless of the pregnancy status.
Replicating PI-3 vaccine.
Modified Live Virus - usually requires only one injection to provide protection. Vaccinate calves when they are over 4 months of age.
Non-replicating PI-3 vaccine.
Killed Virus and Chemically Altered Virus vaccines require two doses initially and an annual booster to provide adequate protection. Vaccinate calves when they are over 4 months of age.
Intranasal PI-3 vaccine.
The resistance stimulated by intranasal PI-3 vaccine is rapid but short lived and generally will stimulate resistance in calves of any age. This is the vaccine form of choice when a PI-3 exposure is anticipated. A booster vaccination with a replicating or nonreplicating form of PI-3 vaccine is required to provide longer protection.
Adding PI-3 to a vaccination program is cheap. In fact, it is easier to find respiratory vaccines that contain PI-3 than it is to find one that does not contain PI-3.
Source: E.J. Richey, Extension Veterinarian, College of Veterinary Medicine, Cooperative Extension Service