Part 2 - When too much of a good thing turns bad
In my last post, I began discussing that when it comes to canine and feline vaccines, too much of a good thing can be problematic. To restate what I mentioned before, vaccinations at the appropriate times, for the appropriate animals, in the appropriate circumstances are of the utmost importance to preserve health and well-being. Responsible vaccination protocols have enabled us to safely and effectively protect our pets from infectious diseases. The puppy and kitten vaccine series, for example, should always be given. Puppies and kittens who do not receive this series are at critical risk of contracting one or more deadly infectious diseases. [Let’s also not forget foals and young farm animals in this equation.]
The concern relates to the overuse of vaccines in these immunologically naive youngsters and adult dogs and cats, as well as to vaccines given to aged pets and those with already compromised immune systems. This is when you, as your companion animal’s trusted guardian, should understand what is appropriate and put the breaks on giving unnecessary vaccines.
Let’s take a look at the two types of vaccines – modified live-virus vaccines (MLV) and killed vaccines – and their potential effects on your pet’s health.
As the name suggests, MLV vaccines use a modified, but weakened, form of the live microorganism. When the virus is injected into the body, it multiplies many-fold and stimulates the immune system’s production of antibodies, creating an immune response that protects the body against future exposure to the disease.
For dogs: Distemper virus, adenovirus-2 (hepatitis, canine respiratory virus) and parvovirus are all MLV canine vaccines, as are intranasal bordetella, intranasal coronavirus (not recommended by 2011 AAHA* Canine Vaccine Guidelines), and parainfluenza virus. The first three vaccines plus rabies vaccine are the so-called “core” vaccines for dogs. (Note: a recombinant canine distemper virus vaccine is also available.)
MLV vaccines have been associated with the development of temporary seizures in both puppies and adult dogs of breeds or crossbreeds susceptible to immune-mediated diseases – especially those involving hematologic or endocrine tissues such as immune-mediated/autoimmune hemolytic anemia (IMHA/AIHA), immune/idiopathic thyrombocytopenic purpura (ITP), a low platelet count and autoimmune thyroiditis. MLV vaccines – given singly or in combination – are also increasingly recognized contributors (albeit rarely) to immune-mediated blood disease, bone marrow failure and organ dysfunction. When MLV vaccines are given to pets with compromised immune systems, the animal is actually at risk of contracting a weakened form of the virus from the vaccine.
The introduction of MLV vaccines more than 20 years ago is linked to increasing allergic problems and immunological disease in companion animals. Dogs with pre-existing inhalant allergies (atopy) to pollens display an increased risk of vaccinosis (an adverse vaccine response).
Killed vaccines use an inactivated “ dead” form of the virus (previously live microorganisms that have been killed with chemicals or heat), along with an adjuvant (a substance added to a vaccine to enhance its effectiveness without itself causing an immune response).
For dogs: Killed vaccines include all rabies vaccines, canine leptospirosis, Lyme, canine influenza, injectable bordetella, injectable coronavirus (not recommended by 2011 AAHA* Canine Vaccine Guidelines) and diamondback rattlesnake toxoid (does not protect equally against all types of rattlesnakes, including Mohave green variety).
For cats: Unlike canine vaccines, most vaccines for cats come in MLV (not recommended for pregnant queens or very young kittens), killed and intranasal versions. Vaccines for feline panleukopenia virus (a parvovirus, often incorrectly called feline distemper), feline viral respiratory disease complex (feline herpes virus and calicivirus) plus rabies vaccine are considered as “core” feline vaccines. Killed and so-called ‘lifestyle’ (see below) vaccines also include those for feline leukemia virus (a recombinant version is also available), feline immunodeficiency virus, chlamydia and intranasal bordetella (these latter two are not recommended for routine use).
As with MLV vaccines, killed vaccines can trigger both immediate and delayed adverse reactions. Of highest concern are the vaccine injection-site sarcomas most commonly seen after rabies vaccination in cats, but also seen occasionally in dogs. Genetic predisposition to these disorders in humans has been linked to the leucocyte antigen D-related gene locus of the major histocompatibility complex, and is likely to have parallel associations in domestic animals. Killed vaccines can at worst aggravate an already existing autoimmune disease and may prove ineffective.
Although all dogs are susceptible to vaccine-related side effects, breeds at highest-risk of vaccinosis (in alphabetical order) are:
• American Cocker Spaniel
• German Shepherd
• Golden Retriever
• Irish Setter
• Great Dane
• Kerry Blue Terrier
• Dachshunds (all varieties, but especially the long-haired)
• Poodles (all varieties, but especially the Standard Poodle
• Old English Sheepdog
• Scottish Terrier
• Shetland Sheepdog
• Shih Tzu
Breeds with white or predominantly white coats, as well as those with coat color and pigment dilution such as fawn (Isabella) or blue Dobermans, the merle coat color, blue Yorkshire Terriers, grey Collies, harlequin Great Danes, and Australian Shepherds are also more susceptible.
Note: Breed-susceptibility data are generally unavailable for vaccinosis in cats.
People often ask me about the non-core vaccines, such as leptospirosis, Lyme disease, bordetella (a component of kennel cough) and canine influenza. These vaccines are considered “lifestyle” vaccines and should be assessed according to your dog’s individual risk factors. Does your dog play at a dog park with other animals? Is he boarded in a kennel? Does he attend doggy daycare? Does your geographic location have increasing outbreaks or incidences of a particular disease? All of these factors should come into play when deciding whether to vaccinate your pet against the lifestyle vaccines. Most non-core vaccines require annual revaccination to maintain immunity, so be sure that your dog really needs them.
In my next post, I’ll discuss appropriate alternatives to current vaccine practices, including the use of titer testing in lieu of vaccinations. Stay tuned!