Last week, I took a look at canine diseases and vaccines. This week, I will discuss how vaccines and titre testing work. I will talk about feline disease and vaccinations at a later date.
You can read Part 1: Canine Diseases and Vaccinations here.
Part 2: Vaccines and Titre Testing
What is titre testing?
An antibody titre test is a blood test that determines the concentration (titre) of antibodies in the blood. Antibodies, also called immunoglobulin, are used by the immune system to fight off pathogens such as viruses or bacteria. A high antibody concentration (high antibody titre) indicates either: 1) recent exposure to a pathogen, or 2) immunization is up to date.
How vaccines work
A vaccination contains either a weaken or killed form of a pathogen such as a virus or a bacteria. The vaccination will not cause severe illness but will give the immune system a “practice run” at fighting the disease. The immune system will create antibodies to fight the disease. These antibodies are specific to a particular pathogen; for example, rabies antibodies are only effective against the rabies virus and are not effective against other diseases. A high antibody titre (concentration) will provide the patient with immunity to that specific disease. A low titre or zero titre will not provide immunity.
The duration of immunity (DOI) is the length of time that the patient will be have sufficient antibodies to be immune to the disease. DOI is influenced by the cause of disease, the patient’s vaccine response, and the patient’s antibody retention. Diseases can be caused by viruses or bacteria. Vaccines that provide protection against viruses, such as rabies and distemper, have a long DOI. Bacterin vaccines provide protection against bacteria, such as leptospirosis and bordetella, and have a short DOI. Vaccine response will vary from patient to patient. Some patients will be more responsive to vaccination than others; their immune systems will create a higher quantity of antibodies. These patients will have higher antibody titres upon vaccination then less responsive patients. Finally, retention of antibodies will vary. Simply put, some patient will create antibodies that last longer than other patients.
Vaccination schedules are created using the DOI for most patients. However, it is possible for a patient to have a longer or shorter DOI than average. Patients with long DOI will not require vaccination as frequently as indicated by guidelines. These patients could be considered to be overvaccinated if vaccinated on the average schedule. A small percent of patients will have a shorter DOI than average. These patients have a poor response to vaccination and will require vaccination more frequently than indicated by guidelines. The only way to determine the DOI of a vaccination for an individual patient is by titre testing. Following vaccination, the titre for some patients will stabilize at a sufficiently high level and will remain constant for years, so the patient would not respond to vaccination by significant increase in titre.
Please refer to my previous post for more information on canine diseases and vaccinations.
Overvaccination
The canine (and feline) vaccinations available on the market today have an excellent safety record. However, adverse events following vaccination (vaccine reactions) are still possible. There are a variety of adverse events associated with vaccination.
Adverse events in the days immediately following vaccination can include lethargy, mild fever, loss of appetite, and pain at the injection site. More severe reactions such as anaphylaxis (allergic reaction causing swelling of the face and neck) can also occur. Other adverse events that may be more long term include immune-mediated hemolytic anemia and injection site sarcomas (tumours). Severe reactions to vaccination are rare.
Overvaccination occurs when an animal who has sufficient antibody concentration to provide immunity to disease is given a vaccine. For example, the 2011 AAHA Canine Vaccination Guidelines recommends vaccination for DA2PPv every 3 years. Testing has shown that inoculation in dogs for DA2PPv is effective for at least 3 years but the exact duration will vary from animal to animal. In some cases, antibody concentration will be high for longer then 3 years. In these cases, it is not necessary to vaccinate the dog until antibody concentration drops. A titre test will indicate the antibody level and allow vets and owners to decide if the animal requires vaccination. Some dog owners prefer to avoid over-vaccination to decrease the risk of adverse reactions to vaccination and will elect to titre test before vaccination.
Titre Test Availability
Until recently, titre testing was only available by sending a blood sample to an outside laboratory such as the Atlantic Veterinary College lab at UPEI, or Idexx Laboratories in Ontario. There are now in-clinic test kits available which simplify the testing process and allow titre tests to be performed in-clinic.
In Canada, Canine VacciCheck titre test became available in 2013. There are currently no in-clinic feline titre tests available in Canada. Canine VacciCheck is a modified ELISA test that detects titres for canine distemper, adenovirus, and parvovirus. While titre testing is still more expensive than vaccination, in-clinic titre testing is less expensive than testing done at an outside laboratory.
As rabies is a reportable disease and all rabies cases must be reported to Health Canada and the Canadian Food Inspection Agency, rabies titre testing can only be performed at specialized laboratories. There are no in hospital rabies titre tests, and none will ever be developed.
Bacterin vaccinations have a short DOI. This makes titre testing for diseases such as bordetella and leptospirosis impractical. In-clinic titre testing is not available for these diseases and many outside laboratories do not offer the service.
Titre Testing, Vaccination & Your Dog
While some dog owners will choose to continue with vaccination on a regular schedule, other will prefer to use titre testing to customize their dog's vaccination schedule to their dog's individual needs. If antibody titres are high, vaccinations can be given less frequently and veterinarians and dog owners can rest easy with the knowledge that their dogs are still protected against disease. For a dog who has received all of his or her puppy vaccinations, titre testing can be used to determine if additional vaccination is required to provide inoculation through sufficiently high antibody titres. All dogs will benefit from the decreased risk of adverse reactions to vaccination that a customized schedule will provide. Elderly dogs, dogs with a history of vaccine reactions, dogs with chronic disease (such as liver disease), dogs with compromised immune systems, or dogs with other illnesses will also benefit from titre testing. Here are examples of some patients that would benefit from titre testings:
- Example 1: Rex
- Rex is a 4 year old healthy adult Border Collie, that goes to doggy day care, agility trials and long walks in the park. He was last vaccinated 3 years ago, and his owner wants to make sure that he is well protected from getting sick since he is in contact with a lot of dogs, especially at the park. His owner also has concerns about overvaccination.
- Example 2: Jewel
- Jewel is a 1 year old Bichon Frise, who had a reaction to her last set of puppy needles when she was 4 months old. Her face swelled up, and her owner would prefer not to see that again, but also wants to make sure Jewel can go for walks in the park.
- Example 3: Jake
- Jake is a 7 year old Golden Retriever, who is just entering his senior years. His owner doesn't want to do anything that might cause him to age quicker or bring on arthritis before Jake is ready to slow down.
- Example 4: Blue
- Blue is an 8 year old Yorkie with liver disease, who is taking multiple medications, and who is planning to travel with his owner to the United States for the winter. His owner understands about having Blue's rabies vaccination up to date, but wonders if Blue really needs any other vaccines.
- Example 5: Sam
- Sam is a 2 year old mixed breed mostly Lab sweetie, only had 1 set of her puppy shots at 8 weeks old, and missed the other 2 sets. Her veterinarian would like to know if she needs to have just one set of vaccinations to bring her immunity up to a protective level, or if she needs a series of 2 sets. Sam's owner wants to take her to doggy daycare and obedience classes, and does not want her to get sick, either from catching a contagious disease, or from overvaccination.
If you have any additional questions about titre testing, we would be glad to help you find the answers. If you are interested in titre testing for your dog, please let us know so that we may help you keep your fourlegged family healthy, happy and huggable for as long as possible.
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