Study of Canine Vaccine Antibody Responses
The canine distemper and parvovirus vaccines are high potency, highly effective biological injections that affect the patient’s immune system. Their judicious use should maximally benefit our patients while minimizing overt and subclinical side effects.
This article summarizes a review of canine distemper and parvovirus titer test results for 15 years of patient records. Most dogs remain antibody positive for many years and do not require repeated vaccinations. There are many benefits of titer testing, medically, professionally and financially, for the clinician, the owner and the patient. These results lead to vaccine titer testing and vaccination recommendations.
THE REASONS FOR SELECTIVE VACCINATION
Canine distemper virus (CDV) and parvovirus (CPV) vaccines are considered core vaccines due to the severity of these diseases.1 They are modified live, high potency injections that significantly impact the immune health of the patient and can cause adverse reactions.2,3
The immune system is extremely complex, with the cellular and humoral components interacting and balancing each other. When we inject a vaccine, a high potency antigenic load, we initiate a series of reactions that initially suppress the immune system over ten to 14 days, then stimulate it over the next two weeks.4,5 In most patients, the immune system rebalances itself back to normal. When the immune system is suppressed, for any reason, there is an increased susceptibility to infections. When the immune system is stimulated, for any reason, there is a risk, in predisposed patients, to the development of allergies or auto-immune disorders.1,3
Current distemper and parvovirus vaccines are modified live virus (MLV), high potency products that are highly effective at immunizing and protecting dogs against these diseases.1,3 These attenuated modified live vaccine viruses multiply in the patient’s body, infecting the dog without causing clinical disease. They do result in the production of viral-specific antibodies which can be measured in serum.6,7,8,9,10 These vaccines are now high potency or high titer, with CPV having more than ten million live viruses in each dose.
Our clients are questioning why we vaccinate every dog with every vaccine every year. With a selective vaccination approach at the annual examination, we are frequently not giving any injections. To add value to these consultations, we need to give more attention to a thorough history, nutritional information and physical examination, often including an ophthalmologic examination. We also need to listen to our clients, affirm and compliment their good care of their pets, and show compassion and understanding. Laughing with the client strengthens the vet-client bond. I use the acronym ALL for each appointment: Affirm, Laugh, Learn.
As Dr. Ronald Schultz, professor and chair of the department of pathobiological sciences at University of Wisconsin-Madison states: “Be wise and immunize, but immunize wisely”.11,12 Current (2011) American Animal Hospital Association (AAHA) recommendations for canine distemper and parvovirus vaccination are to vaccinate puppies at 12 and 16 weeks of age, booster at one year if the last puppy vaccine was at less than 16 weeks of age, then re-vaccinate greater than or equal to every three years.1 However, AAHA then goes on to say that the efficacy of the vaccines is at least five years:
- “Among healthy dogs, all commercially available distemper vaccines are expected to induce a sustained protective immune response lasting at least five years.
- “Among healthy dogs, all commercially available MLV-CPV-2 vaccines are expected to induce a sustained protective immune response lasting at least five years.”
PERSISTENCE OF DISTEMPER AND PARVOVIRUS ANTIBODIES AFTER VACCINATION
Total immunity against viral diseases includes:
- Local IgA and IgM
- Humoral immunity of IgG antibodies, both those present in the blood and those that can be produced quickly when the antigen is present
- Cellular immunity or memory
- Other mechanisms.
When we measure antibody titers, we are only documenting the IgG antibodies present in the bloodstream. A negative antibody titer does not mean the patient is susceptible to that disease; it means that no antibodies are present in his blood. That patient may or may not be protected.3 At this time in veterinary practice, serum antibody titers are the only tests we can do.
We have limited information about the length of vaccine protection as it requires either challenge or large epidemiological studies, both of which are extremely expensive. Although a number of publications have looked at whether dogs have protective neutralizing antibodies present after vaccination, this author was unable to find any that sequentially studied CDV and CPV titers in client-owned dogs with known vaccination histories.
Objective: To report on the length of time after vaccination that antibodies persist in dogs.
Data collection: The patient records of Aesops Veterinary Care were reviewed from 2000 to 2014 for CDV and CPV antibody titers measured at the annual examination.
After collection, the serum samples were refrigerated or frozen (if stored for longer than three days) and sent to commercial laboratories by overnight courier. The titers were done at Idexx Laboratories in Ontario or at Hemopet in California. Both laboratories ran positive and negative controls for each batch of samples tested.
The dogs were tested every two to three years. Positive titers can be due to vaccination and/or exposure to virulent virus in the environment. None of the patients had a history of overt disease that was confi rmed as either canine distemper or parvovirus. However, subclinical, mild or undiagnosed disease is possible.
For some of these dogs, vaccinations had been given prior to them becoming patients of Aesops Veterinary Care, so the vaccination history came from other veterinarians, shelters, rescues or pound organizations. The vaccination records of new patients were checked; only dogs with known vaccination histories were included.
Results: The number of years between the last vaccination and the last titer test varies from one to 12. Patients can be lost to follow-up, may die, or the owner, with veterinary consultation, may decide to cease testing since no further vaccinations would be given even if the patient tested negative. This may occur if the patient develops a serious disease such as an auto-immune disorder or cancer. Interestingly, no owner resumed vaccinations at Aesops Veterinary Care once they started titer testing.
Group 1: 15 dogs vaccinated as puppies and not vaccinated since.
- All these dogs tested positive for CDV and CPV titers when they were subsequently tested, one or more years later.
- One dog was positive at the one-year test, but three years after her puppy vaccination (the last of which was at 12 weeks of age), she was negative for both CDV and CPV. She was an English cocker spaniel diagnosed as a puppy with persistent right aortic arch that had been surgically corrected. However, her severe megaesophagus remained a lifelong problem resulting in variable nutrition.
- Of the 14 dogs who always tested positive, tests have been done up to nine years post-vaccination.
a) Nine dogs were positive five or more years after their puppy vaccination.
b) Five dogs were positive eight or nine years after their last vaccination.
Group 2: 31 dogs vaccinated as puppies, given a booster one year later and not vaccinated since.
- Two of these 31 dogs tested negative (7%). A Papillion with epilepsy tested negative for CPV five years after his last vaccination. A German shepherd, also with epilepsy, tested negative for CDV six years after his last vaccination. Both these dogs were receiving phenobarbital to control their seizures.
- Of the dogs who always tested positive, tests have been done up to 11 years post-vaccination. 27 dogs were positive four or more years after their last vaccination, and all 11 who were tested at eight or more years were positive.
Group 3: 30 dogs vaccinated as puppies, given a booster one year later and vaccinated subsequently one or more times.
- Three of these 30 dogs tested negative (10%).
a) A Weimaraner tested negative for CPV two years after his last vaccination. As a result, he was given a vaccine booster. Two and five years later he tested positive.
b) A standard Schnauzer tested negative for CDV six years after his last vaccination. He had inflammatory bowel disease controlled by diet and a low dose of glucocorticoids.
c) A French bulldog tested negative for both CDV and CPV seven years after his last vaccination.
2. Of the 27 dogs who always tested positive, tests have been done up to ten years post-vaccination.
a) 25 dogs were tested and all were positive four or more years after their last vaccination.
b) 16 dogs were protected eight to eleven years after their last vaccination.
Summary of results: Of the 76 dogs, 64 have been tested four or more years after their last vaccination. Of these 64 tested dogs, 61 were positive for a protection rate of 95% Some dogs have remained protected for at least eight years (24) and at least ten years (six). Six dogs tested negative for either CDV and/ or CPV. These were all patients with compromised immune systems due either to a medical condition or their breed.
There are many reasons for decreased or absent antibody responses.
- Maternal antibody overwhelming the vaccine is an increasing risk due to the high potency of our vaccines. This explains the current AAHA recommendation for the final dose of the initial series between 14 and 16 weeks.1,2
- Subclinical viral infection at the time of vaccination, or no antibody response in the rare animal for unknown reasons, results in an unprotected dog.1,2 It is wise to titer test one year after the last vaccine to ensure the patient did respond.
- Medications with cytotoxic actions can interfere with modified live vaccines, including tetracycline (doxycycline) and clindamycin.
- Cachectic conditions such as malnutrition and major illness result in a poor or absent immune response. These patients should be vaccinated when the problem has been resolved. The same applies to any condition or medication causing immunosuppression.
- Chronic disorders decrease the antibody response to vaccination. These include any cause of decreased nutrition such as megaesophagus, maldigestion, malabsorption, liver disease, and protein-losing diseases.2 This study adds epilepsy that’s controlled with phenobarbital to the list (two dogs). Some bloodlines in some breeds have decreased immune systems, including Weimaraners and Rottweilers.1,13 These patients should be titer tested every two years.
Findings conﬁrm the updated selective vaccination recommendations of an annual physical examination and health consultation for each dog.1,2,3 If more than one vaccination injection is required at an annual examination, separate these by four weeks in order to minimize the stress on the dog’s immune system and reduce the incidence of adverse reactions.14
Vaccinate at 12 to 13 and 16 to 20 weeks of age, then titer test one year later. Three years after the last vaccination, do a blood titer level to see if this dog requires revaccination. Repeat the titer test every three years. These recommendations are in line with the 2011 AAHA guidelines.1
The beneﬁts of titer testing are that dogs are not being vaccinated when they don’t require it. Owners perceive the veterinarian to be informed, caring and professional. The veterinarian is being rewarded both ﬁnancially and with the satisfaction of practicing good medicine.
PROTECTION CAN LAST MANY YEARS
Positive titer tests indicate the patient is protected from that infection and disease. The length of time this protection lasts is several years, and possibly the lifespan of the pet.1,3,11,13 It is pertinent to remember that the IgG antibodies are just part of the body’s immune protection; it is the part we can measure. In the protected patient, vaccination has no advantages, only potential disadvantages.