ITHACA, N.Y. -- The northward spread of raccoon rabies can be halted byvaccination barrier zones, veterinarians and wildlife biologists at theCornell University College of Veterinary Medicine are predicting.
A preliminary assessment of vaccine trials in New York, Vermont and Ohio,where oral vaccines are dropped from aircraft into raccoon rabies-freeareas, points to the barrier zone strategy as the most promising way toprevent further spread of the disease, the Cornell experts say. But thevaccination barrier should be extended across northern New Hampshire andMaine, they recommend, before treating East Coast states that already areinfected with wildlife rabies.
"The vaccination barriers appear to be holding," said Donald H. Lein,D.V.M., Ph.D., director of the Diagnostic Laboratory at the CornellUniversity College of Veterinary Medicine, where the anti-rabies campaignfor the Northeast is based. "We're ready to establish the same kind ofbarriers in Maine and New Hampshire. This problem calls for a regionalapproach, because sick raccoons don't stop at state lines."
Or at international borders, either. That's why Ontario and other Canadianprovinces are interested in aiding the U.S. anti-rabies effort, said LauraL. Bigler, Ph.D., coordinator of the Cornell vaccination program. Aparallel effort to vaccinate Canadian foxes has all but eliminated foxrabies from southern Ontario, Bigler reported. Ontario and Quebec haveprovided financial and in-kind assistance to the Cornell project in hopesof keeping raccoon rabies from spreading across the U.S.-Canada border andinfecting Canadian raccoons.
The Cornell wildlife rabies control program uses an oral rabies vaccine,Raboral, that was fully approved earlier this year by the U.S. Departmentof Agriculture's Center for Veterinary Biologics. Capsules of the vaccineare concealed in flavored baits that are dropped from aircraft ordistributed by hand in populated areas. Besides raccoons, the same vaccinehas been shown to control rabies in coyotes as well as red and gray foxes.
Cooperation of several federal, state, county and provincial agencies wasrequired to initiate the rabies-control programs in strategic regions ofNew York and Vermont. Beginning in 1995, Cornell developed a regionalrabies-control strategy for raccoons in the Northeastern United States.
A vaccination zone also has been established in Ohio, said Bigler, whoassisted the effort in that state. "But additional zones are required inMaine and New Hampshire to complete the barrier strategy. Then we canbegin the second phase, gradually moving the vaccination zones southwardinto infected areas to attempt to eliminate this disease altogether," shesaid.
Raccoon rabies was first diagnosed in the United States in Florida in 1947.The viral disease made a great leap northward in the late 1970s, when anestimated 3,500 raccoons were transported from Florida to Virginia. Sincethen, raccoon rabies has spread to parts of every eastern state, from Maineto Florida.
Although coyote rabies is found in Mexico and fox rabies occurs in Canada,neither country has reported the raccoon variant of rabies, Bigler noted,and the Appalachian Mountains serve as a natural barrier to contain raccoonrabies to the East. Consequently, the elimination of raccoon rabies from arelatively small area, the East, may be possible with vaccination, she said.
Compared with the cost of treating rabies in the United States, anestimated $200 million to $1 billion a year, the cost of preventing raccoonrabies is much less but it is not inconsequential, Lein said.
"The vaccine baits are expensive. That's why we're fine-tuning our programby using the smallest possible number of baits per square mile andvaccinating annually, in the fall instead of twice a year to keep theoverall costs as low as possible. We also need to test different baits tosee if there are any 'raccoon favorites,' while also collecting informationabout how far apart the baits can be placed. In the long run, we predictthat a coordinated, unified program to eliminate raccoon rabies will bemuch less expensive than individual state and provincial initiatives thatare performed in isolation," Lein said.
Lein, the Cornell Diagnostic Laboratory director, called for congressionalaction to appropriate federal funds through the Animal Damage Control unitof the USDA's Animal and Plant Health Inspection Service (APHIS). Thatunit, in cooperation with USDA Veterinary Services, universities, producerorganizations, federal and state agencies, already administers eradicationprograms for other diseases that impact people, domestic animals andwildlife, such as brucellosis, tuberculosis and pseudorabies, Lein observed.
"USDA-APHIS-ADC should be granted the authorization and fiscal resources toproceed to carry out their mandate to control this disease withestablished, coordinated programs such as the Cornell control program forraccoon rabies," Lein said. "Vaccination of wildlife will protect people,pets and livestock from this fatal disease."
The above story is based on materials provided by Cornell University. Note: Materials may be edited for content and length.
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