Oral Rabies Vaccination

Oral rabies vaccination (ORV) has been under field investigation in the United States since 1990, in Canada since 1985 and in Europe since 1980. Currently, there are 15 states distributing oral vaccines for raccoons in the U.S., while Texas distributes baits for gray fox and coyote. There have been nearly 48 million doses of Raboral V-RG® distributed in the U.S. and Canada, and 63 million doses have been dispersed worldwide. Raboral V-RG® is currently the only effective oral vaccine licensed for use in free-ranging raccoons, gray foxes, and coyotes in the United States.

V-RG is a recombinant vaccine made from a living pox virus vector, vaccinia (V), that carries the rabies antigen in the form of rabies glycoprotein (RG). The rabies glycoprotein is the protective sheath that surrounds the rabies virus and elicits an immune response when swallowed by raccoons, gray foxes, or coyotes. The vaccine cannot cause rabies because it contains only the non-infective surface proteins of the rabies virus, not the viral nuclear material which would be necessary for the virus to replicate and cause an infection.

The outer bait matrix is made from fishmeal (for raccoons and coyotes) or dog food (for gray foxes) combined with a polymer that acts as a binding agent. The vaccine packet, or sachet, resembles a small catsup package but contains about 1.5 ml of vaccine. The sachet is inside the bait matrix and waxed into place so it does not fall out during aerial delivery. As the raccoon, gray fox, or coyote eats through the outer bait matrix, the inner sachet gets punctured allowing vaccine to enter the animal’s mouth and coat the lymphatic tissue in the throat. There is an immune response to the rabies antigen which creates antibodies to fight off the disease. After two to three weeks the “blueprint” to create rabies antibodies exists in the animal’s immune system which can easily be created should the animal be exposed to a rabid animal.

Baits are distributed by airplanes in rural areas and by hand in urban and suburban areas. Airplanes fly in straight lines or “transects” at about 500 feet above ground while distributing baits. The bait distribution machine is controlled from the airplane and is turned off when crossing a road or house to avoid human contact with the bait. Baiting by hand is done in urban and suburban areas to get the best chance to vaccinate an animal while decreasing human contact with baits. In 2003, more than 10 million baits were distributed in the U.S. and Canada.