September 2017
From the State Vet's Office

Bovine Viral Diarrhea

What you don’t know could hurt your herd.

"What you don’t know won’t hurt you." "Ignorance is bliss." Those statements may be true for a while, but often prove to be incorrect in the long run. You may have heard the advertisement about hepatitis C. The general message is that thousands of baby boomers are infected with the hepatitis C virus and don’t even know it. The suggestion is for people to be checked for the virus. I sort of relate the bovine viral diarrhea virus to that, except in cattle not humans. Thousands of cows, calves, heifers and bulls have the BVD virus and the owners are not even aware of it. I am not saying they should go get themselves checked. However, I am fairly sure that ignorance about the BVD virus is not always bliss.

A few weeks ago, a group of veterinarians from the Alabama Department of Agriculture and Industries and Auburn University got together to discuss what might be done to help the producers in our state to be less impacted by BVD. While we didn’t come away with a plan to rid Alabama of this serious problem within the cattle industry, we did all agree that education was the foundation to dramatically reduce the adverse economic effect this disease wreaks on our cattle producers. I wrote an article about BVD back in 2009 … I think. If you don’t have a problem with the disease or, certainly, don’t own cattle, that article was probably enough to do you for a long time. But we see enough of what kind of problems BVD causes and I believe it is time to do more education. And if you don’t own cattle, read the article anyway. You can impress your cattle buddies when you tell them how much you know about BVD.

BVD can cause transient infection, much like when we get a virus. About a week to 10 days after exposure, the cow or calf or bull gets sick. Then it builds up antibodies and, after about three days, it starts to get better. Transient infections can cause anything from fever, cough, runny nose and slight lameness all the way to hemorrhage, diarrhea and death. Acute outbreaks can be pretty bad, depending on the virus strain. And, depending on the virus, the animal may not even show signs of illness. One of the most aggravating characteristics of the virus is how it can pretty much shut down the immune system. In fact, one study found the most common virus present in feedlot cattle with pneumonia was the BVD virus.

Transient infection is like the virus kids get when they are at school and everybody passes the vomiting and diarrhea around. Then they get well and life goes on. There is another type of infection caused by the BVD virus. That type of infection occurs when the calf is exposed while it is still in the uterus and from 45 to 120-150 days of development. At that particular time in the calf’s development, the immune system has not developed yet. The virus establishes itself and, when the immune system comes along, it recognizes BVD as part of itself. Because of this, the calf can never develop antibodies to the virus. Most of these calves die at or shortly after birth. Those that live, however, shed huge amounts of the virus to infect some innocent bovine they come in contact with. They are persistently infected. We have come up with a term for those calves. We call them persistently infected BVD animals, PIs for short.

The reproductive problems caused by the BVD virus may lead to a lot of train wrecks for the cow/calf producer. If the fetus is exposed before 30-45 days, the calf usually dies and is reabsorbed by the uterus. If it is infected after 120-150 days, it is not unusual to have developmental deformities. Brain abnormalities are probably the most common type. The virus can also cause the calf to be born with cataracts in both eyes, abnormally small eyes or completely blind.

The virus is bad enough that two countries in the world had eradication programs that were reasonably successful. Those countries are Sweden and Denmark. Their BVD eradication programs began in 1993 and 1994, respectively. I will have to admit, though, when I think of those two countries, cattle is not among the first 10 or 15 things that cross my mind. Several states have certainly talked about the feasibility to put together a program to at least reduce the number of animals affected by the virus. As I said earlier, we talk about what we can do to help the Alabama producers with this virus. We constantly discuss with our lab at Auburn ways we might help producers test for the PI calves because they are the most formidable sources of infection.

There are things you, as a producer, can do to stack the deck in your favor against the virus. First, you can buy replacements from seedstock herds tested to eliminate PI calves. Second, you can practice strict biosecurity. If that term is not familiar to you, I will write a biosecurity column sometime in the near future. And finally, you can vaccinate against the virus. There are several good, commercially available vaccines against BVD. There are killed virus and modified-live virus vaccines. Do not give a modified-live virus to a pregnant cow, though. People have been known to cause cows to abort by vaccinating bred cows with live BVD and other virus vaccines. But, for the most part, I cannot overemphasize that you should sit down with your veterinarian and discuss a vaccine program custom-made for your operation.

If you have never had a problem with BVD, this article may not mean much to you. However, if you are one of the producers across the state who has had serious reproductive problems, you know what we mean when we say it is bad. If you are a stocker grower who has had to deal with a respiratory outbreak, you know how bad it can be. So we continue to kick the can down the road.

 

If you have suggestions that might be helpful, don’t hesitate to call me and discuss them.

 

Dr. Tony Frazier is the State Veterinarian for Alabama. You can contact him at 334-240-7253.