Dr. Mike Paul, DVMDog Checkups & Preventive Care

August is the Center for Disease Control’s Immunization Awareness Month, so I figured it is a great time to talk a bit about something that is gaining popularity among pet parents. A procedure that pet owners hear more and more about these days is “titer” testing. But just what are titers? What are they tested for and what do they mean?

What is an antibody titer?
As you might remember from high school biology, the body uses antibodies to attack foreign substances to keep the body healthy. Unlike, say, antibiotics that work against many different bacteria, a dog’s body will naturally create unique antibodies in response to specific, foreign organisms (or actually anything that the body ‘sees’ as foreign). This is a basic part of your dog’s immune system and typically helps your dog to fight off disease. Titer tests may help your veterinarian determine the concentration of a specific antibody in your dog’s blood.

How do vaccines create antibodies in dogs?
The presence of a specific antibody in the blood is a reflection of past exposure to that respective antigen/organism. In fact, it is on this basis that vaccines work – when a pet is vaccinated it is exposed to a modified, “killed” or weaker strain of an organism that causes disease. This allows your dog’s body to develop antibodies to fight it off. These antibodies stay in your dog’s body for a time and usually provide various levels of immunity to the more common or stronger forms of that specific organism.

Why might my veterinarian recommend a titer test for my dog?
Your veterinarian may recommend an antibody titer for a number of reasons:

1. To determine if your dog currently has or has previously had a specific infection. (for example –  Lyme disease, Ehrlichiosis)
2. To determine current immunity against infectious diseases and the need for booster vaccinations (for example – canine distemper, canine parvovirus)
3. To evaluate the efficacy of a recent vaccination (for example –  canine distemper)
4. To detect the presence of antibodies that may be fighting against tissues or cells in your dog’s own body (for example – autoimmune diseases, like IMHA)
5. To determine immune status against rabies and others for travel purposes.

Titer tests for dogs measure levels (not just presence) of a specific antibody
When those antibody levels are measured by running titers on your dog’s blood, the result is more than just positive/negative. Titers determine the concentration of the antibodies in the blood sample by diluting the sample over and over again and testing it each time to find the highest, most diluted sample that will still react with the antigen in question. A higher end point dilution equals more antibodies present in the original sample as a stronger immune response. If the antibodies are protective ones, then your dog may be more likely to have immunity to that specific bug.

What do antibody titers tell your dog’s veterinarian?
Antibody titers can play an important role in determining your dog’s immune status or exposure to a particular infectious organism. If antibodies are found (a positive test result), you and your vet learn a lot:

• Your dog has had some prior exposure to that infection– whether by a previous vaccine or coming in contact with it otherwise.
• If specific antibody levels are high enough after a known vaccine has been given, this will indicate that your dog is likely to be protected from that infection and may not need a booster yet.
• If it’s unknown whether your ailing dog has been vaccinated against the disease prior to the test, your veterinarian will likely take two blood samples and run tests a few weeks apart to determine whether there is an “active” infection that might need to be treated. Generally, a four fold increase in titers between paired samples is a good indication of recent or ongoing infection.
• If you have a newly adopted puppy (from a shelter), however, the rising titer might also mean he was just vaccinated.

Your vet will interpret any titers in light of his known history and any clinical signs of illness.

Questions to ask your veterinarian:

1. How do you feel about scheduled booster vaccinations versus titer testing for my dog?
2. What are the pros and cons of titer testing instead of revaccinating on a regular schedule?

If you have any questions or concerns, you should always visit or call your veterinarian — they are your best resource to ensure the health and well-being of your pets.