Blacksburg, VA -- Epidemiologists in the Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech have contracted with Fairfax County Health Department officials on a $75,000 project designed to help control a raccoon rabies epidemic in the area by conducting a wildlife rabies vaccination program.
The goal of the Fairfax County Oral Rabies Vaccine Program is to help protect citizens and companion animals in the Fairfax County area from exposure to the deadly virus, according to Dr. Francois Elvinger, an associate professor in the college's Department of Large Animal Clinical Sciences. Fairfax County, a suburban area near Washington D.C., accounted for almost 20 percent of the state's reported rabies cases during 1999.
While rabies is largely controlled in domestic animals through mandatory immunization programs, it remains difficult to control in wild animal populations such as raccoons, skunks, foxes and bats. Effective wildlife vaccines have been developed, Elvinger said, but getting the vaccine into the animal remains a significant challenge.
Epidemiologists have determined that delivering oral rabies vaccines through baits is the best way to approach the task. Elvinger, who is collaborating with scientists at the Centers for Disease Control in Atlanta on the project, plans to deliver the vaccine in roughly one-inch square blocks made of a fish-meal polymer. As the raccoons chew the wafer, the vaccine, which is enclosed in a plastic sachet, will be released and the animal will become immunized to rabies.
In April, public health workers and volunteers will begin distributing 17,000 vaccine doses over an area which covers about one-sixth of Fairfax County in an effort to achieve a distribution density of one bait per two and a half acres. Officials plan to target an area bordered by the Potomac River on the east, the Occoquan River on the south, Interstate 95 to the west, and Interstate 495 to the north.
"We hope to get a large enough percentage of the raccoon population so that the epidemic will be reduced,"said Elvinger, who is a Diplomate in the American College of Veterinary Preventive Medicine. "There will always be raccoons coming in from areas that are not vaccinated."
The four-phase distribution process is expected to include aerial drops from helicopters based at nearby Fort Belvoir, ground-based crews seeding known "raccoon activity zones," citizens who feed raccoons, and public works personnel who frequent areas considered prime raccoon habitat.
The oral rabies vaccine to be used in the program is a licensed biologic that confers immunity via a recombinant virus that cannot cause rabies in people and animals and is not hazardous to healthy people, pets, and wildlife. About 20 million vaccine baits have been distributed in the wild since the early 1990's without any recorded adverse affects.
However, Elvinger said, people with weakened immune systems, such as those with HIV/AIDS or those undergoing chemotherapy, pregnant women, and young children should avoid contact with the liquid vaccine inside the bait. The bait blocks also contain a tetracycline biomarker to assist researchers in measuring the success of the program. Data regarding the incidence of rabies in the target raccoon population is being gathered on the basis of serologic testing, and post intervention evaluation will examine factors like the existence of the biomarker, serological testing, the numbers of animals submitted for evaluation, and the number of human and animal exposures. Depending upon the results of the first vaccine distribution and continued funding by the Fairfax County Board of Supervisors, the program may be expanded to other parts of the county in the future.
Similar programs recently conducted in other areas of the country have yielded excellent results, said Elvinger. Wildlife rabies vaccination programs conducted in Maryland's Anne Arundel County were responsible for a reduction in rabies positive raccoon cases from 14 per year to one per year. In Pinellas County, Florida, reported cases dropped from 30 a year to two a year following a wildlife vaccination program.
Rabies is a viral disease of mammals which attacks the central nervous system. It is almost always fatal and is transmitted through the bite of an infected animal. Clinical signs include changes in behavior, general sickness, problems swallowing, increased drooling, and aggression. Affected wild animals may appear tame and pets may appear more violent.
Virginia has had a significant wildlife rabies problem for the past 30 years or so, according to Elvinger. In 1999, 529 rabies cases were reported in wildlife, 35 cases were reported in domestic animals, and 17 additional cases were reported in bats. Of those 581 reported cases, 107 were reported in Fairfax County.
In 1997, a rabid fox which wandered into a yard where a children's birthday party was being held ignited public concern, which eventually led Fairfax County public health officials to contact the Virginia-Maryland Regional College of Veterinary Medicine, according to Elvinger. To minimize risks of exposure to rabies, people should avoid contact with wildlife, advise local animal control officials of animals that are acting strange, have domestic animals vaccinated, and make sure trash cans and pet food are not in position to attract wild animals. People bitten by animals should contact a physician, and pets bitten or scratched by wild animals should see a veterinarian.
Additional information on the program can be obtained by calling the Fairfax County Oral Rabies Vaccine Information line at 703-246-5333 or by visiting a web site at http://www.co.fairfax.va.us/service/hd/rabies01.htm