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February 2010 Archive for Cattle Healthline

RSS By: Dan Goehl, DVM, Beef Today

Dan Goehl, DVM, and his wife own and operate Canton Veterinary Clinic in Canton, MO, where Dan works primarily with stocker and cow/calf beef operations.

What's a Farmer to Do?

Feb 08, 2010

Reader asks:

Got a Question?
Send an e-mail to ask veterinarian Dan Goehl your animal health question.

 

We vaccinated our beef herd last spring with a nine-way vaccine. We also vaccinated for pinkeye two times using a vaccine our vet recommended. We haven't had any pinkeye in years. We have a closed herd, but in July we had a terrible outbreak; almost half of our herd got infected. The vaccine company did a culture and it was determined that the infection was different than what the vaccine covered.

If a new vaccine is developed, should we use it, or do nothing? I am discouraged with these vaccines that are no help to our herd's health. I shouldn't have vaccinated! What's a farmer to do?

Dan's response:

I have been in this situation before and this is a very frustrating position. It can happen with any vaccine, but pinkeye vaccine may very well be the most common scenario. There are a couple of things we need to discuss. 

First – why do vaccines fail? Vaccines can fail because we administered the wrong vaccine, because it was administered improperly, because it is not an efficient vaccine or because the challenge level of the disease was simply too high for the animal to ward off (this is not a complete list!). Secondly – the pinkeye vaccines that are on the market are killed vaccines, so they cannot make the problem worse.

The most commonly recognized infectious agent to cause pinkeye is Moraxella bovis. In recent years other bacteria in this family have also been incriminated near the top of the list. Other diseases that can cause similar signs are IBR virus, Mycoplasma and vitamin deficiencies. Moraxella offers a unique challenge because it has dozens of different strains. This makes it very difficult to make a vaccine that will protect against all of the variations. What is causing a severe outbreak on one farm may be a different strain from what the operation across the road is suffering from. 

Moraxella is spread from animal to animal in a variety of ways. The most common is that of the face fly. The face fly feeds on eye secretions and irritates the surface of the eye in the process. Eliminating face fly problems removes one of the main mechanisms of transfer for the disease-causing organisms. The face fly provides some unique challenges in trying to control, primarily because it spends a very small percent of its lifetime on the cow.

In this case you administered the correct vaccine, in a sense. You used a commercial, reputable product for the disease you were trying to prevent. One of the  biggest issues with pinkeye is that there are many strains of bacteria that cause this problem. Although companies often have multiple strains, they still are gambling the strain that you are going to have problems with is one of the strains in your vaccine. Assuming you administered the vaccine correctly, handled it correctly and gave it within proper time constraints, the most likely scenario is the strain that affected your herd this year was not in the vaccine. The other possibility is the disease challenge was simply too massive for the immune system of the animal.

I know that at times it can appear that the vaccine has exasperated the problem (and at times credit is given that is not due). We never truly know what would have happened had the vaccine not been given. The incidence could have been worse or the lesions more severe. Pinkeye tends to be cyclic on a farm, going years without any disease and then suffering severe outbreaks. This may last a season or a couple seasons, and then at times it will vanish again. This makes assessment of our plan even more difficult. 

In the end, although you may feel that the vaccine in question did not benefit the herd, I can ascertain you that it did not cause the problem.

Protection from disease is our ultimate goal. This is accomplished when we can keep the challenge from disease below the level of immunity. Disease challenge is something that exists in every herd. Immunity is also present in every herd, vaccinated or not. Our goal is to raise the level of immunity, lower the challenge of disease, and not allow these two lines to cross.


Dan Goehl, DVM, and his wife own and operate Canton Veterinary Clinic in Canton, Mo., where Dan works primarily with stocker and cow-calf beef operations. Dan is also a partner in Professional Beef Services, LLC, which offers herd consultation and helps in data management and marketing of beef cattle.

This column is part of the Beef Today Cattle Drive eNewsletter, which is delivered to subscribers biweekly and includes beef industry analysis and market information as well as the latest beef headline news. Click here to subscribe.
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