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Preventative medicine worth a pound of cure

By Daniel H. Grove, DVM - May 5th, 2016 - Ask the Vet

AskTheVetBenjamin Franklin said, “An ounce of prevention is worth a pound of cure.”  I wonder if he really knew how true that is.  Preventing disease is usually much easier on an animal, much more economical, and just a more favorable way to care for our animals.  Today I am answering two questions by discussing vaccinations and deworming, two common preventative medicine measures used by most horse owners.

First, let’s discuss vaccinations. A vaccine contains usually two parts, an antigen and an adjuvant. The antigen(s) is/are the disease or diseases you are vaccinating against. It can either be a killed piece of an organism or toxin, or it can be a living organism that is modified to be less pathogenic, or less likely to cause disease. The adjuvant is put in to stimulate the body to react to the antigen. Without it, the body’s response to the antigen would be minimal and would yield very little immunity to the disease.

The American Association of Equine Practitioners (AAEP) has established a “core” set of vaccines recommended for all horses. The diseases vaccinated for in the program are Eastern and Western Encephalitis, Tetanus, Rabies, and West Nile virus. Most all of the vaccines I have used are recommended to be used annually to maintain immunity against these diseases. There are vaccines for other diseases, but they are recommended based on risk. Some examples are Influenza, Rhinopneumonitis, Leptospirosis, and Strangles. Most of these are also done annually. Two examples of ones commonly done more frequently are Influenza and Rhinopneumonitis.

Vaccines should be strategically given so that they will have the best protection when the horses are at greatest risk. Diseases that are transmitted via a vector, like a mosquito, should be vaccinated against just prior to the onset of the time of year when the mosquito population is highest and most active. So for diseases such as Eastern and Western encephalitis or West Nile, usually we vaccinate in the early spring. This allows the body time to mount its response to the vaccine and have the greatest immunity just before the spring and summer months. Vaccines for Influenza and Rhinopneumonitis should be given just before your horse is going to be exposed such as in transport or at a rodeo or show. These diseases are transmitted by close contact or aerosols, much like the common cold in humans. Diseases like Tetanus or Rabies do not have a specific time of year that tends to be worse than others, so their timing is not as important.

Vaccines are mostly against diseases caused by bacteria and viruses, but another group of organisms we can prevent disease from are parasites. Parasites are organisms that live off another organism and cause harm in the process. Most parasites we are able to regularly kill off with our dewormers are the ones that are worm-like. In horses, the common ones we are concerned with are roundworms, tapeworms, pinworms, strongyles, and bots. In the past, the strategy was to rotate between drugs periodically to kill off the parasites according to what parasites are common for the time of year. The strategy worked well, but the worms have evolved to develop resistance to the drugs we have to treat them with at this point.
The current recommended strategy to keep our adult horses healthy and yet to minimize drug resistance is to first test for the parasites to see if they are even present. This involves collecting some fresh feces and sending it off to the lab where they will add some special fluid and look at it under a microscope. A trained eye can the look for the typical eggs from the parasites and determine which types are present. Then your veterinarian can recommend what dewormer to use to be most efficacious. This minimizes the amount of drug your horse and the parasites are exposed to, therefore, slowing the speed at which the parasites can develop resistance.

Some instances where you may need to deworm without testing the horse would be a mare around the time of foaling and for young foals. Mares near foaling can reactivate parasites that are in their bodies but not actively growing. These parasites are not susceptible to some of the dewormers It may still be prudent to prophylactically deworm. In the case of the young foals, they have not developed immunity against the parasites yet so deworming them more aggressively can be advisable.

Hopefully, this article has given you some guidance on what you as a horse owner can do to prevent disease before it is ever a problem. I would highly recommend discussing what preventative measures you can take in your specific area with your veterinarian. Different organisms thrive in different environments, so your veterinarian will be able to guide you to the best program.

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