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New Approach to Vaccination of the Canine
by Leanne Bertani, MD
For years, it was believed that annual vaccinations for viral
diseases were necessary to keep our beloved companions out of
harm's way. But we have recently come to a turning point in
vaccination of the canine. While we are grateful for protection
from diseases such as distemper and parvovirus, there is growing
realization that vaccination is not always benign.
In 1996, a study was published suggesting an association between
vaccination and autoimmune disease, specifically autoimmune
hemolytic anemia, an often fatal destruction of red blood cells.
(1) This was followed by another study that demonstrated that
dogs may develop an autoimmune response after vaccination.(2) In
1998, the American Association of Feline Practitioners responded
to the increasing incidence of vaccine-induced fibrosarcomas in
cats by changing the recommendation for feline parvovirus
vaccination from annually to every three years. These events,
coupled with the knowledge that some vaccinations for viral
diseases may protect for seven or more years, have caused
veterinarians and dog breeders alike to begin to ask, "Are we
vaccinating too much?"
Duration of Immunity for Common Vaccines
Studies have shown that, once fully immunized, more than 90% of
canines retain immunity to Parvovirus-2 and Adenovirus-2 for more
than seven years. (Full immunization may not take place with
vaccinations administered prior to 16 weeks, due to interference
by maternal antibodies.) Immunization to Distemper may last up
to 15 years, and immunization to Corona virus probably
lasts a lifetime. Immunization to Rabies and Parainfluenza
lasts about 3 years in about 80-85% of dogs. Note that proven
duration of immunity may vary dependent on the type of
vaccination used; for instance, modified live parvovirus
demonstrated a longer duration of immunity than killed virus; one
strain of distemper tested for a longer duration than another.
New recombinant vaccines may be more efficient and produce a
longer-lasting immunity.
Other vaccines, particularly the bacterial ones, are less durable.
Some vaccines for Bordetella may last less than a year and are
probably only effective in about 70% of dogs. Sufficient data on
Leptospira, Borrelia (Lyme) and Giardia vaccine is not available
to suggest immunization lasting much longer than a year.(4)
Progress in the Veterinary Community
The American Veterinary Medical Association Council on Biologic
and Therapeutic Agents published immunization recommendations
for dogs and cats in 1989, suggesting annual revaccination. The
companies that produce the vaccines also suggest annual
revaccination. A study published in 1998 found that 27% of
vaccinated dogs had a less-than-protective CPV titer, and 21% of
dogs had a less-than-protective CDV titer, and summarized that
the current practice of annual revaccination of dogs against CPV
and CDV infection should be maintained. (5) (Critics of that
study argue that authors used CDV antibody titers that are
inconsistent with sterilizing immunity and don't take into
consideration that those dogs with lower titers will be protected
from disease but not infection.) With the above in mind, it was
understandable that veterinarians were reluctant to buck
tradition, as the legal community generally compares medical
practice to the "standard of care". But the vaccination
revolution received a couple big pushes in 2001. The January
2001 issue of The Veterinary Clinics of North America (Small
Animal Practice) featured vaccinations and discussed the need for
reconsidering traditional annual vaccinations. A chapter author,
Dr. Ronald Schultz, Professor & Chair at the University of
Wisconsin, says that their Veterinary Medical Teaching Hospital
has been on an "every three or more" year vaccination schedule
for cats and dogs for over four years. "The goal for the future
should be to vaccinate more animals than are now vaccinated but
to vaccinate those animals less often and only with the products
that the animal needs," says Dr. Schultz. Another advance came in
April 2001, when the American Veterinary Medical Association
Executive Board approved the Council on Biological Therapeutics
new "Principles of Vaccination." This statement was published in
the Journal of the American Veterinary Medical Association on
September 1, 2001. The principles state that "unnecessary
stimulation of the immune system does not result in enhanced
disease resistance and may increase the risk of adverse
post-vaccination events." It recommended that veterinarians create
"core" and "non-core" vaccination programs (see below for
examples), and that vaccine schedules be tailored to the needs of
each specific animal.
High Priority ("Core") Vaccines
The high-priority vaccines are those protecting against diseases
that are of greatest risk to the dogs or to public health, and
those that carry a large benefit-risk ratio. Possible vaccines
that might be included in many core programs would include:
1. canine parvovirus-2 (CPV-2)
2. canine distemper virus (CDV)
3. infectious hepatitis, controlled by canine adenovirus-2
(CAV-2).
4. rabies (RV) - a priority in all but the "rabies-free"
countries.
At this time, most products intended for vaccinating for CAV-2 ,
also includes Parainfluenza (PI), so vaccination for
Parainfluenza may be included by default.
Rabies vaccine is almost a "no-brainer", as it is considered a
core vaccine in most areas, and is high priority and governed by
state law in the United States. Although there appear to be some
rabies-free areas in Canada, most dogs in the US should receive a
rabies vaccine between 4 and 6 months, with a booster a year
later, and then every three years. There are a few states with a
high rabies incidence that may require an earlier initial
vaccine, and yearly revaccination.
Minimalist Approach
Like many decisions, the vaccination decision comes down to risk
versus benefit. The absolute minimum requirement would be
vaccination with the high priority vaccines at least one time
after the age of 4 months, and revaccination with rabies vaccine
according to area law. Using this minimalist approach, a dog
living in a rabies-free area may only have one injection in its
entire life. This approach might be useful in families of dogs
that are at risk for adverse reactions to vaccines such as
anaphylaxis or autoimmune disease.
But the minimalist approach is risky. Knowing that the
parvovirus vaccine is over 90% effective is not much comfort if
you are in the small percentage whose dog is unprotected and that
dog brings it home to your puppies. Then there is always the
worry that some puppies will contract disease between the ages of
6-12 weeks, when protection by maternal antibodies begins to wane.
And there are some breeds that don't appear to "immunize easily"
(Dobermans, Rottweilers). There is concern that the initial
vaccines may not be effective due to poor handling or other
reasons, and that extra vaccines are necessary for "insurance".
There is also concern that without the vaccines to draw pet
owners in for annual veterinary visits, life-threatening
conditions may go unnoticed.
Titers
Titer tests (blood tests to attempt to determine the dog's level
of immunization) are also becoming more common, but are
inconvenient and expensive in some areas, and remain somewhat
controversial. As yet, there is no consensus on the usefulness of
titers. Critics point out that there have been no studies to
determine what levels actually confer protection from disease, or
if there is even a correlation between antibody levels and
susceptibility to disease. Some maintain that there is a
difference between protection from infection, and protection from
disease. Also somewhat suspect is the lack of standardization for
tests determining antibody concentration. Dr. Richard Ford, of
North Carolina State University, states, "The risk lies in the
fact that a single serum sample divided three times and sent to
three different laboratories is quite likely to yield three
different titers, and quite possibly three different interpretations.
What may be deemed 'protective' by one laboratory could well be
labeled 'susceptible' by another. Furthermore, it is important to note
that a vaccinated dog or cat that does not have a significant
concentration of antibody may, in fact, have excellent immunity.
A 'negative' antibody titer does not necessarily correlate with
susceptibility to infection. Likewise, the presence of antibody,
even at high levels, does not guarantee immunity subsequent to
exposure. (6) At this point, the biggest role of the titer may be merely
to convince boarding clinics or show committees that the animal
doesn't require its annual vaccination. It is likely that titer testing will
receive greater utilization in the future, but further studies are
obviously needed.
Sample Core Protocols: 1998 Colorado State University Protocol
Some universities have already developed new vaccination programs.
One of these is Colorado State University. (7) Their 1998 core
recommendation is a standard three shot series at 8, 12, and 16 weeks
of age, including parvovirus, adenovirus 2, parainfluenza, distemper. A
rabies vaccine was recommended after 16 weeks of age. Following the
initial puppy immunization series, dogs would be boostered one year later
and then every three years thereafter for the above diseases. Bordetella
vaccine was recommended at least 72 hours prior to possible exposure
(dog show, trip to boarding kennel) and could be repeated every two to
four months.
The summary is below:
8, 12, & 16 weeks: parvo, adeno, parainfluenza, distemper
(Proguard 5) After 16 weeks: rabies (Imrab 3) 68 weeks, & every
3 years thereafter: parvo, adeno, parainfluenza, distemper,
rabies Bordetella as required.
Dr. Dodds
Some veterinarians, such as Jean Dodds, DVM, recommend that
vaccines be given separately if possible, to minimize the
consequences to the immune system. This is presently difficult,
as most vaccines in the United States are only available in
combination (polyvalent) vaccinations - sometimes seven or eight
in one injection! But there are a few that are available in
smaller combinations; her recommendations (as of 4/00) for dogs
prone to autoimmune disease are below. (8) Dr. Dodds also
recommends that vaccination be avoided during estrus, pregnancy
or lactation.
9 weeks MLV Distemper/Parvovirus only (e.g. Intervet Progard
Puppy) 12 weeks MLV Distemper/Parvovirus only (e.g. Intervet
Progard Puppy) 16-20 weeks MLV Distemper/Parvovirus only
(e.g. Intervet Progard Puppy) 24 weeks or older, if allowable by
law Killed Rabies Vaccine 1 year MLV Distemper/Parvovirus only
booster 1 year (give 3-4 weeks apart from Dist/Parvo booster)
Killed 3 year rabies vaccine (MLV=modified-live virus)
After 1 year, annually measure serum antibody titers against
specific canine infectious agents such as distemper and parvovirus.
Bordetella, corona virus, leptospirosis or Lyme only if endemic in
the area.
These are only sample core schedules, and recommendations for
any one particular dog should be made by a veterinarian with a valid
patient-client relationship.
Breeders' Compromise
Because of the fear of puppy mortality from distemper and parvo,
many breeders still give annual distemper and parvo vaccinations
to dogs and bitches being bred or shown, but more and more are
choosing to discontinue vaccinations for viral diseases at the
time the bitches are retired, with the exception of rabies where
required by law.
The Lower-priority (non-core) Vaccines
Again it comes down to risk vs benefit. Killed vaccines are more
risky in the short term, ie, more likely to cause immediate
adverse reactions (anaphylaxis/anaphylactic shock) than live
vaccines, and bacterial vaccines more risky than viral ones.
Those generalities would denote Leptospira (killed bacterial) as
the most likely of the commonly used vaccines to cause
anaphylaxis, followed by Borrelia/Lyme's Disease
(killed/recombinant bacterial), and Rabies (killed viral), Corona
and Bordetella. Corona is available as modified live viral, but
the killed viral preparation is commonly used. Bordetella
bronchiseptica is a bacterial vaccine, available as modified live
and killed; the nasal preparation is thought to have the highest
benefit-risk ratio.
The Leptospirosis vaccine is a controversial one. Leptospirosis
is an important disease because it can be transmitted to man and
some other animals, and can cause severe kidney disease. As
mentioned above, it is one of the vaccines most likely to cause a
fatal anaphylaxis in puppies, so many breeders just don't give it.
Until recently, the vaccine only covered two serovars and was
effective in less than 50-75% of dogs that received the vaccine.
But two more serovars have been recently added, and leptospirosis
has become endemic in some areas. Therefore, the decision to
include Leptospira will have to be made on the basis of its
presence in the dog's area, as well as the future performance of
the two new serovars.
The value of the Canine Coronavirus vaccine is also controversial.
Some authors go as far as to say that it is not needed. Corona
is a highly contagious virus, but one that rarely causes death in
an adult dog. It may cause protracted diarrhea, though, and can
be fatal to puppies, so the decision on whether or not to
vaccinate for Coronavirus probably depends on how much exposure
your dogs have to outside dogs, and also whether or not you raise
puppies in your home. Many breeders choose to vaccinate their
adults just one time in hopes that it will decrease the
possibility that they will bring the Coronavirus home to their
puppies.
Vaccinations for Borrelia/Lyme's Disease and Giardia are
generally not necessary for the large population of toy dogs that
spend most of their time on the couch. But some of the sportier
toys and those in endemic areas may be vulnerable, so it is best
to consult with your veterinarian and possibly the Public Health
Department in making decisions regarding Leptospira, Borrelia,
Corona, and Giardia vaccines.
Bordetella bronchiseptica is a bacteria that causes infection of
the trachea and bronchi; the infection is commonly called "kennel
cough", and is kin to the human "whooping cough". The Bordetella
bronchiseptica vaccine is often given when dogs are likely to be
exposed to large numbers of other dogs, such as a dog show or
boarding kennel. It is available both as injection and as a
nasal inhalant. The inhalant vaccine is thought to be less likely
to cause a severe reaction, and also to have less interference by
immunity from colostrum. Immunization to Parainfluenza and
CAV-2 is thought to enhance the protection of the Bordetella vaccine.
Unfortunately, the Bordetella vaccine is not one of the more
efficient ones, having a short duration and about a 70%
protection rate, but I expect we will have more efficient vaccines
in the future.
Considerations for Toy Breeds
It does appear that toy breeds may have more adverse reactions to
vaccines, so a less-frequent vaccination schedule may be of
particular benefit to this group. The most frightening response
is severe anaphylaxis, most common after killed bacterial
vaccines such as leptospirosis. There are some vets who will not
give a leptospirosis vaccine to a dog under ten pounds for this
reason. The one milliliter dose volume listed on most vaccine
labels is recommended because that was the volume tested during
the licensing process. During the efficacy testing, the issue of
breed was ignored. Consequently, we really don't have studies to
tell us if the Toy Poodle should get the same volume as the Great
Dane. Although a natural inclination would be to halve the dose
for toy breeds, there is little or no scientific data to back up
that recommendation. Human studies, though, advise against
decreasing dosage on the basis of size. In a study of premature
babies given half of a DTP vaccination, those babies did not
appear to develop an adequate immune response to Pertussis.
(9) A common compromise used by breeders is to halve the dose
of the vaccination during the initial puppy series, giving a full dose
after 16 weeks. Leptospirosis is usually omitted until after a year
of age, or omitted entirely, unless there is local concern about the
disease. This may change after the performance of the new vaccine
is evaluated.
The Future
The veterinary community is somewhat hampered by lack of
adequate funding for the research needed, but the future should
bring more efficient vaccines. Instead of modified-live virus, we will
probably have vaccines available made from recombinant DNA. We
may also see more nasal vaccines, which may be less likely to
cause adverse reactions. Hopefully, more work will be done to
correlate antibody titers with immunization to clinical disease.
It would also be nice to see some studies done comparing the
prevalence of autoimmune disease between groups of annually
vaccinated dogs, and dogs vaccinated less frequently under the
new proposals. And of course, there will need to be more studies
regarding the actual duration of immunity following vaccination.
We can help by encouraging our breed clubs to contribute to
funding of veterinary research.
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Questions regarding the article may be directed to
LBertani@columbus.rr.com
The above article is merely an exploration of changing trends in
vaccination and should not be misconstrued as advice. Consult
your veterinarian before making changes in your vaccination
program.
References:
(1) Duval D, Giger U. Vaccine-induced immune-mediated hemolytic
anemia in the dog. J Vet Intern Med 1996.
(2) Hogenesch H, et al. Vaccine-induce autoimmunity in the dog.
In: Schultz RD, ed. Advances in Veterinary Medicine 41: Veterinary
Vaccines and Diagnostics. San Diego: Academic Press, 1999; 715-732
(3) Schultz, RD Duration of Immunity to Canine Vaccines, Canine Infectious
Disease Workshop, James A Baker Institute, August 1999(4) Recent
Advances in Canine Infectious Diseases, L Carmichael, editor. Baker
Institute for Animal Health, College of Veterinary Medicine, Cornell University,
Ithaca, New York, USA
(5) McCaw DL; Thompson M; Tate D; Bonderer A; Chen YJ, Department of
Veterinary Medicine and Surgery, College of Veterinary Medicine, University
of Missouri, Columbia. J Am Vet Med Assoc, 1998 Jul, 213:1, 72-5
(6) Vet Clin North Am Small Anim Pract. 2001 Jan p 442
(7)
http://www.cvmbs.colostate.edu/vth/savp2.html
(8)
http://ighawaii.com/naturally/doddsvac.html
(9) Pediatrics 1989 April 83(4) 471-6 Half-dose immunization for
diphtheria, tetanus, pertussis: response of preterm infants. Bernbaum J, Daft A,
Samuelson J, Polin RA
Thank you Dr. Bertani for sharing this excellent information with
Cavaliers Online readers!
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