USDA Distributing and Testing Oral Rabies Vaccines for Wildlife

The US Department of Agriculture has begun its annual oral rabies vaccine program for wildlife, according to a news release from the Animal and Plant Health Inspection Service (APHIS). The department is also field testing a newer marshmallow-flavored vaccine aimed mainly at raccoons and skunks.

Since 1995, APHIS has distributed oral rabies vaccine baits in selected states through the National Rabies Management Program. The program is designed to limit the spread of raccoon-variant rabies in the eastern United States; it also targets rabies variants in coyotes and foxes. Baits are dropped from aircraft in rural areas and delivered by hand in more densely populated locations.

The oral rabies vaccine currently being used in the United States is Raboral V-RG (Merial Inc, Duluth, GA), a live, recombinant, vaccinia virus—vectored rabies glycoprotein vaccine licensed for use in raccoons and coyotes and safety tested in over 60 species. Distribution of Raboral V-RG eliminated canine-variant rabies in coyotes in the United States and has limited the spread of raccoon rabies. However, it has been less successful in skunks. Raboral V-RG is formulated as fish-flavored cubes or sachets.

The agency is field testing another oral rabies vaccine, the Ontario Rabies Vaccine Bait (ONRAB; Artemis Technologies, Guelph, Ontario). This live, recombinant, human adenovirus—vectored rabies glycoprotein vaccine has yielded higher vaccination rates than Raboral V-RG in both raccoons and skunks in Canada, where it is licensed for use. ONRAB is manufactured as a blister pack with a sweet marshmallow-flavored coating.

A 2011 field trial of ONRAB in West Virginia yielded a 49.2% rabies antibody prevalence in raccoons, which was significantly higher than the 9.6% prevalence before bait distribution. In a comparison trial of the two oral vaccines in Maine and New Brunswick, Canada, rabies antibody prevalence in raccoons was significantly higher in the area baited with ONRAB (74%) than in the area baited with Raboral V-RG (30%). A comparison study in Vermont and Quebec also showed that rabies antibody prevalence in raccoons was higher with ONRAB (51%) than with Raboral V-RG (38%). The ongoing APHIS field trial of ONRAB is being conducted to support its future licensure in the United States and to evaluate its safety and efficacy in raccoons, skunks, and other species.

Distribution of Raboral V-RG baits in the eastern United States began in August and will continue until mid-October. The distribution schedule is included in the APHIS news release. The ONRAB trial will cover parts of Vermont, New Hampshire, New York, Ohio, and West Virginia. The field trial news release includes location details and a photograph of the baits. Although humans and pets cannot get rabies from the vaccines, APHIS requests that people who find the baits leave them undisturbed. Anyone making contact with the baits should wash the contact area with soap and warm water.

​Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC.