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Medical Index
First Posted Oct. 9, 2009
Mar 4, 2015

Titer Testing in Horses

by Debora Johnson

Recently my horse, A Patchy, had another reaction to one of his shots, West Nile Virus. He has had this shot many times in the past. Fort Dodge was the manufacturer of the vaccine used. It is a dead vaccine. His neck swelled up over a period of four days, had heat in the swollen area and was somewhat tender to the touch. We administered bute paste: 1 gram of bute paste two times a day for 3 days. The swelling has come down and the heat is basically gone, although there is still a knot at the site of injection. In the past he had several reactions from the Rhino/Flu, as well. Now I do not give him Rhino/Flu any more. That also was a nasty reaction. Repeated exposure to the vaccine could cause a worse adverse reaction so I had to weigh the risks.

This is a concern to me because West Nile Virus is in our area and he really needs to have that as one of his core shots. Kate, who owns the farm where my husband and I board our horses, suggested that we consider titering A Patchy to try to determine if he has enough immunity to be able to forego some of these shots. She and I are going to discuss this with several vets. This set of events got me thinking that researching titering in horses might make a good article for HorseHints.

I wanted to determine how much the titering would cost, which diseases could be titered, how often would titering have to be done, and how accurate were the results of the titers?

"A titer is a measurement of the amount or concentration of a substance in a solution. It usually refers to the amount of medicine or antibodies found in a patient's blood... Antibodies are a type of protein. They are produced by the immune system in response to foreign substances that may be a threat to the body -- such as chemicals, virus particles, spores, or bacterial toxins. (These foreign substances are called antigens.) Each type of antibody is unique and defends the body against one specific type of antigen."

I have one more avenue to explore. Ft. Dodge was the maker of the shots that were used. I am going to discuss with my vet the use of another manufacturer other than Ft. Dodge. It is quite possible that he is reacting to adjuvants added to the shot. What is an adjuvant? "In immunology, an adjuvant is an agent that may stimulate the immune system and increase the response to a vaccine, without having any specific antigenic effect in itself. The word 'adjuvant' comes from the Latin word adjuvare, meaning to help or aid. 'An immunologic adjuvant is defined as any substance that acts to accelerate, prolong, or enhance antigen-specific immune responses when used in combination with specific vaccine antigens.'

Adjuvants have been whimsically called the dirty little secret of vaccines in the scientific community. This dates from the early days of commercial vaccine manufacture, when significant variations in the effectiveness of different batches of the same vaccine were observed, correctly assumed to be due to contamination of the reaction vessels. However, it was soon found that more scrupulous attention to cleanliness actually seemed to reduce the effectiveness of the vaccines, and that the contaminants - 'dirt' - actually enhanced the immune response. There are many known adjuvants in widespread use, including oils, aluminum salts, and virosomes, although precisely how they work is still not entirely understood."
Immunologic Adjuvant

How Are Titers Used for Your Horse?

My husband and I recently had one of our horses titered for Lyme Disease. My husband's horse, Rusty, was showing displeasure about being brushed. It was a behavior that had never been displayed in the past. Touchy skin is one of the symptoms, in horses, that presents with Lyme Disease. There is a high incidence of this disease in our area, Northern Virginia. He showed no exposure when the titer came back. We were quite relieved.

For More Information:

Note: "The question of vaccine titers is a controversial one. There is conflicting data on the protective titer level. Vaccine titers are available for the following diseases: Equine herpes III (rhino), Potomac horse fever, Equine encephalitis (EEE, WEE, VEE), Equine viral arteritis, Equine influenza, Rabies titer (RFFIT: non export), West Nile virus antibody titer, Strangles and Lyme disease. Titers for influenza and equine herpes virus drop off very rapidly and will often result in revaccination. It is often best to determine the disease risk for your horse then vaccinate accordingly. For example, if your are in a rabies free area, rabies vaccine may not be necessary.

Many vaccines do contain mercury as a preservative. The modified live vaccines usually do not. Most tetanus vaccines do have mercury. You can find out if a vaccine has mercury by looking at the company web sight for the technical information they must list contents there by law. Manuel Himenes, DVM, Kailua, HI" AAEP/Ask the vet

"Titer Testing in Horses" Natural Horse Magazine, Volume 11, Issue 2 An excellent, comprehensive article on titering in horses.
[Beyond Vaccination] Re: Vaccinations and laminitis/Elinda
PubMed, "Antistreptolysin O titer in Horses."

"It is interesting to note that "there is much we need to learn about the effectiveness and safety of vaccines. Drug companies do not test vaccines to see how long they are effective, so checking titers on horses may be a way to avoid annual vaccinations. Vaccination programs should be geared to fit each individual situation." Thuja Occidentalis - Arbor Vitae

It cannot be stressed enough to always discuss your horse's care with your vet!

Medical Index