Rabies is a fatal disease of the central nervous system. It is contagious to all mammals, including humans. Dogs receive vaccinations every one to three years. A rabies titer test is another option. The rabies titer test is used to help evaluate the dog's level of immunity to rabies, to facilitate travel into countries with little or no rabies, and to determine whether a vaccine successfully produced antibodies in a dog. The use of rabies titer testing to determine immunity and vaccine protocols is controversial.
A rabies titer test is a blood test that looks for the presence of antibodies in your dog's bloodstream. The results are measured in International Units per milliliter. According to PetTravel.com, a titer of greater than or equal to 0.50 IU/ml is considered acceptable in most countries. A titer measures both the immune reaction caused by natural exposure to the rabies virus and immunity caused by vaccination.
There are three basic purposes for running a rabies titer test. One is to evaluate a dog's level of protection against rabies. According to the Journal of the American Veterinary Medical Association, rabies vaccines can cause side effects, some serious, in a small percentage of dogs. These side effects include vomiting and diarrhea, swelling and pain at the injection site, lethargy, and even circulatory system shock, collapse and death.Owners who have dogs who've had reactions in the past may use titer results to avoid additional vaccination. Second, many countries that have little or no rabies--like Australia, Guam, France, and the United Kingdom--will use rabies titers to screen incoming dogs. Combined with current vaccines, the titer can shorten the quarantine period. Third, rabies titers can be used to check on whether or not a vaccine produced a proper immune response in a dog.
There are problems associated with rabies titer levels. Immunity can originate from exposure to the virus or from vaccination. Titer testing cannot distinguish between the two. Also, there are two levels of immunity produced in a dog--the antibody reaction and a cell-mediated reaction. A rabies titer only measures antibodies, so a dog with a low titer could still be protected if he has a good immune response at the cellular level. Because of that rabies titer testing may not be an accurate predictor of protection.
According to the CDC, there are several factors involved in a dog's immune response to rabies virus, and current tests aren't able to measure and interpret those other factors, so estimated immunity may not be accurate. In addition, Critter Advocacy says it's not known if the 0.50 IU/ml titer will actually protect a dog who's exposed to rabies virus. So titer testing should not be used as a substitute for keeping rabies vaccines current.
Legally, a dog is required to be current on his rabies vaccines in order to be licensed. Rabies titers aren't accepted in licensing of healthy dogs. Dogs that have medical issues, like immune-mediated disorders, or dogs who have a history of severe reactions to rabies vaccinations may be able to get an exemption with documentation from their veterinarian. In these cases a rabies titer may be accepted in place of a rabies vaccine.