Rabies is an important disease that is almost always fatal. An important part of rabies control programs is mandatory vaccination of pets such as dogs, cats and ferrets. In general, rabies vaccination is very safe and effective. Complications from rabies vaccination are rare, but in recent years concerns have been raised about vaccine-associated sarcoma, a type of tumour that can develop at the site of vaccination. Since this complication was recognized, the vaccines themselves and the way they are administered have been changed in order to decreased the likelihood of this problem occuring, but the risk cannot be eliminated completely. For this reason, some people have tried to avoid having their pets vaccinated for rabies.
A blood test can be performed to determine antibody levels (also called a titre) against rabies virus. However, there is not enough information available to determine what antibody titre is high enough to say that an animal does not need to be re-vaccinated. Skipping rabies vaccination based on blood test results is dangerous and not recommended. While rabies is uncommon in most areas, exposure can occur, even in strictly indoor animals (e.g. if a bat gets into the house). Rabies vaccination is a legal requirement in most areas of Ontario. The implications of rabies exposure in an animal that is not “up-to-date” on its vaccines can be severe, including prolonged quarantine or euthanasia. I do not know of any jurisdictions that allow rabies antibody levels to be used in place of vaccination, and animals that are not recently vaccinated are treated as non-vaccinated, regardless of their antibody titre. The risk to your family or your pet from rabies is greater than the very tiny risk of vaccine-associated sarcoma. If you care about your pet and your family, make sure your pet is properly vaccinated against rabies.
More information about rabies can be found on the Worms & Germs Resources page.