Letters: 07/00

Rabies Vaccine
I was grateful for the article in your February issue regarding vaccines. My Morgan mare has had severe reactions to vaccines in the past. I requested a rabies vaccine prepared without aluminum adjuvants or mercury-based preservatives as your article suggested. Unfortunately my vet’s office has been unable to locate a vaccine that does not have either an aluminum adjuvant or a mercury-based preservative. I have been hunting on the Internet, but I have also been unsuccessful. Could you give me the names or distributors of any companies you are aware of that carry such a vaccine’

-Catherine Tremonti

Unfortunately, there is no rabies vaccine approved for use in horses without adjuvants or preservatives. Research on response to rabies vaccines consistently shows better antibody titers when an adjuvant is used. Unfortunately, severe reactions to rabies vaccines are fairly common in horses anyway, so it is difficult to distinguish between what might be related to an adjuvant or preservative and what to the antigen itself. Speak to your vet about the reactions and the possibility of pretreating the horse with an anti-inflammatory that will not interfere with the immune response.

One specific precaution, however: If your horse is developing lumps/granulomas/masses at the injection sites, at least ask your vet what vaccine was used before and avoid products with that preservative or adjuvant. You can also request that they check around for preservative/adjuvant-free versions of the other vaccines your horse receives, or avoid those adjuvants and preservatives that had been present in vaccines causing a bad reaction in the past.

Some good news for the near future is that researchers are working on biological adjuvants — proteins or fats from the cell walls of common bacteria. These bacterial products are already being used as nonspecific immune stimulants in injectable products. There still might be reactions but more of an “allergic” or nonspecific inflammatory than toxic nature, and there are no long-term harmful effects.


Strangles Immunity
In the February 2000 vaccinations article, you state that natural strangles infection provides lifelong immunity. I heard this is not necessarily true.

-Paula Vervaet
Georgetown, NY

Some horses that are said to have had strangles twice probably never had it in the first place. There are also probably horses who appear to have recovered from strangles but have a smoldering abscess that eventually grows and comes to a head. (This can happen internally, too, and make the horse sick on and off for years.) It is a proven fact that strangles immunity (like chicken pox or measles for people) is lifelong, but situations could combine to weaken that immunity enough so a horse could become infected.

By “situations” we mean either a severe loss of immune function caused by aging or serious illness/injury, in some cases maybe even a simultaneous challenge by more than one organism that overwhelms the defenses enough that one or the other can take hold. However, for most horses, a natural infection provides a solid-enough immunity that you should not need to vaccinate.


Fibar Price
In our May 2000 article on footing, the cubic yard and full-arena prices for Fibar were correct, but a mathematical error made the price per square foot incorrect. It should be 20.8?? to 23.9?? per square foot.

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