Canine Vaccination and Titre Testing
The World Small Animal Veterinary Association (WSAVA) states that a single vaccination of Parvovirus, Distemper or Hepatitis (DHP) vaccine, when given to a pup after 16 weeks of age, can last up to a lifetime. Why then do we vaccinate every year for leptospirosis and every three years for DHP?
Vaccination: The Basics
Let’s start with the basics. Vaccination is a process that vets and doctors use to trick the body into producing protective immune responses against infection. It’s a phenomenon that’s been known about for hundreds of years, but the English doctor Edward Jenner in the 1790s made the process famous. Let’s use his experiments to help us understand the workings of vaccination.
Jenner noticed that milkmaids and people working with cattle who had contracted cowpox did not become infected, noticeably, by the much more deadly smallpox virus. He had been alerted to this phenomenon from accounts of manipulating infection in other parts of the world, for example, Turkey and China.
He did an experiment in 1796 whereby he gave cowpox to a young boy, James Phipps, to see if it would protect him from subsequent infection with smallpox. It was a risky experiment to young James, but it paid off. The boy was first inoculated with cowpox, and then a few weeks later was given a dose of smallpox that would typically have caused severe disease, if not death. The boy survived, and so began the dawn of vaccination in the western world. Interestingly, the word vaccination comes from the cowpox virus, which is called ‘vaccinia virus’, from the Latin ‘vacca’ for cow.
Jenner’s experiment demonstrates you can protect against infectious disease and not have to go through the risk of being infected with dangerous bugs to generate effective immunity. Vaccination is now standard throughout the western world and has arguably saved millions of human and animal lives.
When an infective bug enters the body for the first time the body reacts and produces antibodies in the blood from B cells. It also generates a tissue-based response from so-called T cells. Both of these reactions are held in the memory of the body in the lymph-nodes and within the muscle, organ and connective tissues. If the body comes across the same or similar bug later, a much quicker and more effective response is seen the second time.
Nowadays, doctors and vets use either subunits of bacteria or viruses or modified or killed organisms to provoke a vaccine response, not whole, live bugs, further reducing the chance of dangerous infection. Some doctors and vets are suspicious of subtle and long-term side-effects of vaccines. They think some vaccines may cause significant disease in some individuals. Most conventional doctors and vets don’t believe this to be so.
Titre testing is when a vet takes a dog’s blood sample to measure the blood antibody response to a given bug or vaccine it has seen historically. Antibodies for Distemper Hepatitis (Adenovirus) and Parvovirus response are easily measured. If these are present in significant numbers, it can then be said that there is adequate immunity in that patient and further vaccination is not needed in the short or medium term. Antibodies can last for years. Indeed, they can persist for an entire lifetime. Taking antibody titres (measurements) is not just a ‘snapshot’ on the day of the test because immunity persists for years, often for life.
Titre testing in dogs can be repeated every 1 to 3 years, or more, to ensure enduring immunity. This is what the WSAVA is referring to in its Vaccine Guidelines (freely available online at www.WSAVA.org) as we mentioned at the top of this piece.
Every Three Years for DHP?
When I was first in practice in the 1990s, we used to vaccinate with DHP and leptospirosis every year. Almost 20 years ago there was a big hoo-hah, led by campaigner Catherine O’Driscoll, which challenged the science behind annual re-vaccination. After much wrangling with the vaccine companies, it was decided that the vaccine manufacturers would change their recommendations for DHP to vaccinating ‘no more frequently than every three years’. This is generally interpreted as meaning the DHP vaccines should be given every three years. This is not the WSAVA recommendation! They recommend, because vaccination for DHP diseases can last up to a lifetime, three years is the most frequent that anybody should be giving the vaccinations. This is different from recommending vaccinations every three years, of course.
The WSAVA strongly recommend the use of titre testing to avoid over-vaccination. They recommend that titre testing commences at approximately 15 months of age (one year after puppy shots finish) and is repeated as necessary in subsequent years so that appropriate minimal vaccination regimes can be devised for each individual.
Leptospirosis is the disease dogs get from rat urine. Dogs who habitually play or work in muddy ditches, brackish water or persistent puddles are potentially at risk. Nobody knows quite how prevalent leptospirosis is in the UK. Vaccine manufacturers have produced two vaccines to leptospirosis. The older vaccine is called L2, the newer one L4. Incredibly, both were only trialled for 12 months. The recommendation from the vaccine manufacturers is to vaccinate with these vaccines every year (because manufacturers haven’t tested them for longer). Both are known to provoke more adverse reactions than DHP vaccinations, especially in toy dog breeds.
Practical DHP Vaccination
At my practice, we offer titre testing universally to all dogs to try to reduce the amount of unnecessary vaccination. Not all practices follow suit, although it’s becoming more accepted. My titre testing recommendations are in line with the wall WSAVA guidelines.
The WSAVA actually state they recommend minimal vaccination. In my practice, this involves titre testing at 15 months and then every 1 to 3 years after that to assess antibody levels. It’s a straightforward system. It’s economic, and it avoids the unnecessary use of potent medicines (vaccines) which can strongly influence the immune system. Just because vaccines can protect from disease doesn’t mean we should just use them willy-nilly. Vets are trained to only use medicines when needed and when appropriate. I think the routine use of DHP vaccines every three years without titre testing is excessive.
Talk to your vet about titre testing to help with vaccine decisions. They will know about it, and the practice may well offer it as an alternative to vaccinating blind. If they don’t, it’s easy to Google practices that do offer titre testing. For the sake of the appropriate use of these life-changing medicines, I think titre testing is the way forward when it comes to the vaccine question.
Suppose you have just adopted a dog with an unknown vaccination history. In that case, it’s more appropriate to test for DHP antibodies than it is to simply vaccinate and hope for the best. Vaccination for leptospirosis is another matter and needs to be discussed with your vet, as we discussed above.
Practical Leptospirosis Vaccination
If you are wrestling with the decision of whether to vaccinate for leptospirosis or not, discuss with your vet and other vets in the area how often they diagnose leptospirosis in their practice. Also, consider the lifestyle of your dog. The more your dog is exposed to mucky ditches and brackish water, the greater the probability they may be exposed to the leptospirosis bugs.
The BSAVA, the British Small Animal Veterinary Association, considers leptospirosis to be a core vaccine, like DHP. They recommend annual dosing for all dogs. Other countries consider it to be non-core and should only be given to at-risk dogs.
Whether you decide to vaccinate with DHP every three years without testing or whether you decide to use titre testing to minimise vaccination, it is essential to always take steps to do two things. First, avoid infectious disease in your dog through careful, well-considered management. Secondly, minimise problems from potential side-effects of vaccination by minimal vaccination. In the above paragraphs, we discuss questions you need to ask of your vet when making the decision to vaccinate with leptospirosis or not.
As I say to all my clients when discussing vaccines, ‘If you vaccinate you may get problems, if you don’t vaccinate you may get problems’.
Vaccination is a thorny issue, and I’m sure the arguments on how to best vaccinate will rage for years to come.
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