Letters: 06/00

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Lyons ”Ad” Removed
I have subscribed to Horse Journal since the first issue. I always felt that a fundamental part of Horse Journal was not to accept advertising. In my opinion, this is the crucial element to your success in testing products and in having subscribers trust your information. As with Consumer Reports, accepting advertising directly undermines your credibility.

While I do not have an issue with John Lyons personally, I find that by selling his books in your magazine (April 2000) you are by association promoting his product choices. Please reconsider this position. I am disturbed by what I feel is a real threat to your objectivity as a product-testing magazine.

-Mary S. Piro
Acton, MA

John Lyons’ Perfect Horse is a sister publication of Horse Journal, both magazines published by Belvoir Publications. Despite our belief that some readers would find these books worthwhile, we realize our commitment to our readers and will not repeat the ad in the future.

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Vaccinations And Antibody Levels
I have just finished reading your article on vaccinations (February 2000). Of special interest is the frequency guide for rabies and tetanus. I believe all animals should be wisely vaccinated. Yearly vaccinations of any type are usually recommended because the percentage of protection declines after the first, second, third, and beyond years. You recommend yearly rabies and tetanus vaccinations. UDSA and CDC data is available for dogs and cats for one to three years post vaccinations for rabies and tetanus. I have not found any data for horses, other than first year only.

-Barb Peck
Westford, VT

Protection afforded by a vaccine is usually defined as the level of antibody detectable in the blood. The first is whether a drop in antibody titer is an indication to revaccinate. Like a natural infection, vaccinations produce a rise in antibody titer and that antibody titer will drop over time after the initial challenge. However, this is not synonymous with then having no protection.

To determine how well a level of antibody measured in the blood predicts immunity, you would have to expose the animal to a test infection, or measure the antibody response to the booster immunization, to see if he was still protected or not. This is rarely done.

The closest you can come to this would be studies that compared the antibody response to a natural outbreak of disease in previously vaccinated or unvaccinated people, or looking at antibody response to a booster vaccine in the same two groups. In these circumstances, it is often found that the immune system “remembers” the previous vaccines for nine, 10, even 25 years. The bottom line here is that a drop in antibody titer is not a reliable measure of how strong an immune response the horse could produce if challenged.

With specific reference to tetanus and rabies in horses (rabies, by the way, can be given every three years after the initial vaccination if your veterinarian is using that particular vaccine), we don’t really know how long the protection lasts. Could it be longer' Probably, but since we don’t know for sure, and the consequence of inadequate protection is death, we have to stick with the current annual recommendations.

Could we be doing harm by vaccinating this often' Possibly. Hopefully, as the issue of over-vaccination and potential side effects grows, someone will take the time, and invest the funds, to do the research to find out for certain.