Healing Springs sponsored a lecture for cattle owners this past month. At Galax Elementary School, Kenneth Redman from Pfizer Animal Health, described a new vaccination that immunizes unborn calves, that stopped 100% of BVD deaths in controlled trials, and that could realistically prevent all future BVD deaths on farms.
Modified Live vs. Killed: Since Bovi-Shield® Gold FP™ is a modified live vaccine, and since many producers are still on the fence about modified live, Redman started by describing how and why modified live works better. He described the immune system as having three main players:
1. Antibodies: Antibodies catch viruses in the blood stream and neutralize them. Killed vaccines help the body produce antibodies.
2. Macrophages: Macrophages eat the remains neutralized by antibodies.
3. Killer Cells: Killer cells recognize infected cells, break their walls, and enable antibodies and macrophages to digest and clean-up the contents of infected cells. Modified live vaccines help the immune system create both antibodies and killer cells specific the disease targeted by the vaccine.
The big shortcoming of antibodies is that they can only attack viruses free-floating in the blood. Antibodies cannot reach viruses inside cells. Viruses live inside cells. They only get in the blood stream when they are trying to infect more cells. Some viruses can even create bridges between cells. With these bridges, viruses can infect neighboring cells without getting in the blood stream and without exposing themselves to antibodies.
This is why killer cells are so important. Infected cells put of proteins that killer cells “smell.” Each killer cell has one disease that it seeks out. When it encounters a cell that smells like its disease, the killer cell breaks the walls of the infected cell. The contents of the cell spill into the blood stream where antibodies and microphages can neutralize and consume the viruses. Both killed vaccines and modified live vaccines teach the body to create antibodies. Only modified live vaccines teach the body to create killer cells. Modified live vaccines allow the animal to have a more robust immune response.
Bovine Viral Diarrhea (BVD): BVD compromises reproductive performance. Persistently Infected (PI) calves are the largest reason for the spread of BVD. Calves become PI calves in the womb. PI calves are formed when the cow has or is exposed to the BVD virus. Even a very small amount of the virus can create a PI calf. The cow does not need to be sick to create a PI calf. When the unborn calf is exposed to BVD, the calf’s immune system learns to recognize BVD as a normal part of its own body. It does not fight the BVD as a normal immune system would. For this reason, a PI calf will always be a PI animal, and there is nothing anyone can do about it. The PI calf can spread BVD to other members of the herd, undetected for a long time.
Bovi-Shield® Gold FP™: This new vaccine works by protecting both the cow and the unborn calf. When a pregnant cow is vaccinated with Bovi-Shield® Gold FP™, the unborn calf also receives the BVD immunity. When used consistently and correctly, Bovi-Shield® Gold FP™ is supposed to eliminate the problem of PI calves for good. The vaccine was shown to be safe at 1,000 x the recommended dosage. The vaccine provided 100% protection from BVD-PI in Pfizer’s controlled study.
A pregnant cow should not be vaccinated with Bovi-Shield® Gold FP™ unless she was vaccinated with it once before she was bred. The first dose must be delivered while the cow is open. It provides 12 months of protection. No booster shots are required. With this vaccine, it is safe to re-vaccinate pregnant cows. Do not give calves on the ground modified live, unless their dams were previously vaccinated with modified live. If a calf receives a modified live vaccination while nursing a dam that did not receive modified live vaccination, the vaccine could revert to the virus and get back up in the cow through the teat.
For reasons noted above, the vaccine will do no good for an animal that is already a PI animal. At the meeting, Jamie Cassell, DVM stated that PI animals receiving BVD vaccinations will become terribly ill. These animals should be culled.
Modified live vaccines are less stable than killed vaccines. They must be used within 24-hours of being mixed. Keep them refrigerated until delivered. Keep them in a cooler, on ice, when vaccinating.
Healing Springs Animal Hospital is uniquely dedicated to farming and farmers. Anytime you have questions on herd health, call Healing Springs.