Continued from page 2If the polyomavirus in the vaccine is killed, why do some aviculturist discuss side effects?
I must assume that "side effects" is referring to the local response (swelling, etc) at the site of vaccination that can occur when the vaccine is administered intradermally (within the skin) rather than subcutaneously (under the skin). ALL vaccines are designed to cause a reaction. When your dog or cat is vaccinated with an inactivated (killed) rabies vaccine, your veterinarian will probably tell you that your animal may limp for several days after the injection or that you may notice a lump under your animal's skin where the injection was given. When you or your child is vaccinated, it is likely that your doctor will tell you that the injection site may be tender or swollen for several days to several weeks but that the reaction should subside without incidence. Any soreness, redness or swelling that may occur at the vaccination site is the body's normal response to the foreign protein (inactivated virus) that has been injected.
The key to developing a good inactivated vaccine is to combine an inactivated virus with an adjuvant (a mixing agent designed to stimulate the immune system) and inject them into an animal in a site that causes a mild reaction which stimulates the immune system, without causing any severe reaction that will adversely affect the vaccinate.
In developing the avian polyomavirus vaccine, we tested 8 different adjuvants and evaluated the vaccine for intramuscular and subcutaneous use. I have now been using a polyomavirus vaccine in experimental or field settings for more than 5 years. I have vaccinated thousands of birds, one group was vaccinated 5 times during a 7 week period, with no severe reactions. Additionally, a polyomavirus vaccine has now been commercially available for more than 2 years and there have been no reports of severe reactions. If the vaccine is administered subcutaneously, the reaction that the vaccine stimulates in the body will remain undetected. If the vaccine is injected intradermally, a swelling or knot may form at that site of injection. These knots generally resolve without treatment.
Why don't we test for polyomavirus before we vaccinate?
The advantage to testing for polyomavirus is that it provides you with more information about your birds. However, after you have performed all the testing, any birds that have not previously been infected with the virus are still susceptible to infection. The advantage to vaccination is that a successfully vaccinated bird will be protected from infection. As an example, the test that is currently available for HIV (the virus that causes AIDS) is quite good, yet we are spending hundreds of millions of tax dollars each year to develop a vaccine that will prevent HIV infections. Why? Because you could be tested for HIV today and be negative; however, if you are exposed to the virus any time after being tested you would still be susceptible to infection. If you were exposed to the HIV virus 1 month after being vaccinated, you would have minimal concern. The same is true for polyomavirus; testing provides information at the time of sampling, vaccination is designed to alter the future by protecting birds when they are exposed to the virus.
As for specifics on whether to test or vaccinate for polyomavirus, there are two types of tests that can be used to provide you with varying information about your bird's status with respect to avian polyomavirus. These two types of tests (a test to detect antibodies to the virus in serum or the DNA probe test to detect virus nucleic acid in excrement or tissues) were developed by members of our research group. The DNA probe test that we developed can be used to demonstrate the presence of polyomavirus nucleic acid in the excrement, blood or other tissues. We recommend the use of excrement samples because detecting the virus nucleic acid in the feces provides one with more clinically important information than detecting it in the blood. If you choose to use a test to determine whether or not you need to vaccinate a bird for polyomavirus, then the test you need to use is one that detects the presence of antibodies to the virus. If a bird has antibodies to the virus, then it has already been infected and need not be vaccinated. Having been involved in developing and or evaluating the virus-neutralizing antibody test, the fluorescent antibody test, the DNA probe test and the vaccine for polyomavirus, I can tell you that the best and most economical way to control this virus is through vaccination. As a researcher interested in collecting as much information as I can about the health status of companion birds, I suggest that one test and vaccinate. However, if you are an aviculturist with financial restraints, it is preferable to vaccinate rather than test.
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