Rabies Titer Test
What do the Micro Rabies Screen Test (MRS) results mean?
The MRS test is a serum neutralization assay based on the RFFIT designed to give a rapid screening for evaluating the need for rabies boosters. Work done at Kansas State Veterinary Diagnostic Laboratory (KSVDL), at Kansas State University, indicates dogs and cats that have been vaccinated for rabies in the past but are not current on their rabies vaccination status respond similarly to a booster as animals that are current on their rabies vaccination. We (KSVDL) suggest that both groups (non-current and current) can now be referred to as “pre-exposure” vaccinated animals.
Although revaccinating dogs and cats that have been exposed to rabies is effective for disease management, the concern is how to protect our pets from unknown exposures. In human medicine, titers are recommended on a periodic basis to confirm adequate response to rabies vaccination. The level defined as an adequate response is 0.5 IU/mL. This titer level is also recognized by OIE as protective in currently vaccinated dogs and cats based on challenge studies.
A review of rabies challenge-studies in currently vaccinated dogs and cats indicates that there is a positive correlation between rabies virus neutralizing antibody (RVNA) titers and the level of protection after virus challenge.
Pre-exposure vaccination coupled with a RVNA titer at or above 0.5 IU/mL is expected to provide greater assurance of protection than does current vaccination status alone.
The MRS test measures RVNA.
The recognized RVNA level of protection for rabies is 0.5 IU/mL. If the level is below 0.5 IU/mL a booster may be indicated depending on the pets rabies exposure risk level. Consult local rabies vaccination laws and regulations for final guidance.
Currently whether an animal requires a rabies booster vaccination is not determined by the level of RVNA in the serum, but by local regulations which can vary by interval and credentials of who may administer the vaccine. Some states allow exemptions to their rabies vaccine requirement based on the potential to compromise an animal’s health status. Veterinarians are obligated to be familiar with and follow legal requirements for vaccine administration accordingly. The Compendium of Rabies Prevention and Control recommendations, used as guidance for local regulations, are routinely reviewed with consideration of new information. Kansas State Veterinary Diagnostic Laboratory is part of this process to influence change that will provide the best guidelines for rabies booster requirements.