MATENAL ANTIBODY: OUR BIGGEST OBSTACLE
The biggest problem in protecting a puppy against this infection ironically stems from the natural mechanism of protection that has evolved. As mentioned previously, puppies obtain their immunity from their mother’s first milk, the colostrum, on the first day of life. This special milk contains the mother’s antibodies against parvovirus and until these antibodies wane to ineffective levels, they will protect the puppy.
The problem is that they will also inactivate vaccine.
Vaccine is a solution of inactivated virus, either live and weakened (“attenuated” or “modified”) or killed. This virus is injected into the puppy. If there is still adequate maternal antibody present, this vaccine virus will be destroyed just as if it were a real infection. There will be a period of about a week when there is not enough maternal antibody to protect the puppy but too much to allow a vaccine to work. (This period is called the “window of vulnerability.”) Then after this, vaccine can be effective.
The next problem is the age at which vaccine can be effective is different for each individual puppy.
To get around this, we vaccinate puppies in a series, giving a vaccine every 2-4 weeks until age 16 weeks. By age 16 weeks, we can be certain that maternal antibodies have waned and vaccine should be able to “take.” It should be recognized that some individuals, especially those of well vaccinated mothers, must be vaccinated out to 20 weeks (unless a “high titer” vaccine is used.)
After a puppy is born, maternal antibody levels drop by half approximately every 10 days.
Puppies that were born first or were more aggressive at nursing on the first day, will get more maternal antibody than their littermates.
Mother dogs vaccinated at approximately the time of breeding will have the highest antibody levels to pass on to their puppies.
*** REMEMBER, the more maternal antibody a puppy has,
SHOULD LIVE OR KILLED VACCINE BE USED?
Killed vaccine is the least effective at penetrating maternal antibody. It is also associated with more vaccine reactions (since more stabilizing chemicals are used in a killed vaccine). We recommend using live parvo vaccine only unless there is any question about the immunologic competence of the dog to be vaccinated and the dog is an adult. Killed vaccine should probably not be relied upon for puppies.
WHAT IS A HIGH TITER VACCINE?
In the mid-1990’s a new innovation in parvo vaccination was developed: the “high titer” vaccine. The term “high titer” refers to the amount of virus in the dose of vaccine and means that there is a great deal more virus than in the standard vaccines. When the puppy is vaccinated, maternal antibody binds the virus present. If a high titer vaccine is used, there is still virus left over after all the maternal antibody has been used up. This extra virus can then stimulate the puppy’s own immune system. High titer vaccines commonly produce full protection by age 12 weeks (though we recommend carrying vaccination out to age 16 weeks to be certain - an especially good idea for breeds predisposed to infection such as the rottweiler, doberman pinscher and American pit bull terrier).
Currently the following biological companies make high titer parvovirus vaccines:
It should be noted that giving vaccine more frequently than every 2 weeks will cause interference between the two vaccines and neither can be expected to be effective. This includes giving vaccines for different infections. Vaccines should be spaced 2-4 weeks apart.
It is commonly held that puppies need a certain number of vaccines for protection to be achieved (usually either 3 or 4 is the “magic” number). The number of vaccines given has nothing to do with protection. In order for protection to be achieved, vaccine must be given when it can penetrate maternal antibody.
VACCINATING ADULT DOGS
Classically, parvovirus vaccine has been administered annually to all dogs. Vaccine against canine parvovirus has been included in the distemper combination vaccine (the “DHLPP”, “6 in one” etc.)
There has been some thought that predisposed breeds should be vaccinated every 6 months. Vaccinating every 6 months was common in the early 1980’s when the virus was new and in some clinics this policy has simply persisted. Others like to vaccinate certain breeds every 6 months (as mentioned, predisposed breeds include American pit bull terriers, rottweilers, and doberman pinschers). Others prefer to run vaccine “titers” to determine if a vaccine should be given or not.
There has also been some thought that annual vaccination is not necessary, especially for a disease where adult dogs are considered low risk. Many university teaching hospitals have switched to an every 3 year schedule for adult dogs. There is still controversy regarding this practice, especially given possible financial impact to most veterinary hospitals. Do not be surprised if your veterinarian has chosen to follow the university and begin recommending a 3 year vaccination protocol for this virus.
WHAT IS THE MEANING OF A VACCINE TITER?
A vaccine titer is a blood test that measures the antibody level a dog is carrying against a certain virus. There are two methods of measuring parvovirus antibody titer: Hemagglutination inhibition and Serum Neutralization. The value refers to how diluted the dog’s serum (blood) must be for antibody to still be detectable. Based on work at Cornell University, the following titer levels are generally considered protective:
Hemaggluination Inhibition titer of 1:80 or more
Serum Neutralization titer of 1:20 or more
There is a great deal of controversy regarding whether or not a certain level of antibody can be considered tantamount to protection. Many veterinarians do not feel it is useful to run titers until this issue is resolved (ie there is more to protection than an antibody level; there is an entire immune system involved and there is no simple way to assess the entire immune system). Other veterinarians find it cost ineffective to recommend titers prior to vaccination (it costs a great deal more to run the titer than to simply give the vaccination. If the titer is adequate, the worst possible outcome is that the vaccine will be ineffective.) Other veterinarians question whether or not it is harmless to annually give vaccinations when there is already adequate immunity present. At this time there is no single answer to this issue and we recommend trusting your own veterinarian’s educated opinions regarding these issues.