How does oral rabies vaccine work?
The Fairfax County Oral Rabies Vaccine Pilot Program uses Raboral VR-G®, the only oral rabies vaccine licensed by the US Department of Agriculture. Raboral VR-G® is manufactured by Merial, Ltd., Iselin, NJ. It is made using live vaccine virus that is genetically altered through the addition of a part of the rabies virus that stimulates immunity to the disease of rabies. This type of vaccine is referred to as a recombinant vectored vaccine, that is, "re-combined" genetic material from the rabies virus and the vaccinia viruses carried by the vaccinia virus, the "vector." When a raccoon takes oral rabies vaccine into its mouth, the vaccinia virus enters the raccoon's cells. The cells then produce a part of the rabies virus called rabies virus glycoprotein that then causes the raccoon's immune system to begin producing disease-fighting antibodies against the rabies virus. The raccoon thereby becomes immune to rabies. Because the raccoon's disease defense system has learned how to fight the rabies virus it does not get rabies if it comes into contact with a rabid animal thereafter.
What does the story of little James Phipps have to teach us?
Centuries ago, it was seen that people working with cows, mostly milkers, who became infected with cowpox, a viral disease of cows, appeared to be protected from the usually deadly disease of smallpox. In 1796, Sir Edward Jenner, an English researcher and country physician, infected an 8-year old boy named James Phipps with matter taken from fresh cowpox lesions on a dairymaid's hands. James developed a light fever and some pustules at the site where the cowpox virus was given but otherwise recovered. When Jenner inoculated James six weeks later with matter from smallpox lesions the boy did not get sick with smallpox. Of course today nobody could do such research, however, the discovery of how to vaccinate against smallpox was a great breakthrough and became the foundation for many life-saving vaccines developed since. A strain of the vaccinia virus, the virus that causes cowpox and similar to that used in the smallpox vaccine, is used in oral rabies vaccine to carry the genetic material of the rabies virus. Three to four individuals per million who received the smallpox vaccine developed vaccinia-related reactions, usually similar to those experienced by young James Phipps. As was the case with reactions to smallpox vaccine it is possible that contact with liquid oral rabies vaccine, especially if there is a break in the skin such as a scratch, could cause a reaction at the site, for example, the development of some pustules.
Is there a risk to people from the oral rabies vaccine or the bait?
The bait material that encloses the oral rabies vaccine is made of fishmeal and is harmless. Contact with liquid oral rabies vaccine contained inside the bait is to be avoided. However, with over twenty-two million baits containing oral rabies vaccine distributed in the United States since the early 1990s, there has been only one reported instance of a reaction following contact with the liquid vaccine: a Mid-West woman experienced a skin reaction when she was bitten as she attempted to remove a bait from her dog's mouth. Although never reported to have occurred, persons with severely compromised immune systems, such as those undergoing chemotherapy, those with HIV/AIDS or other conditions causing weakened immunity, could be at risk should they contact the liquid vaccine. It is also advisable that young children and pregnant women avoid contact with the liquid oral rabies vaccine. No adverse effects have been recorded among personnel working in oral rabies vaccine programs, even when significantly exposed to the liquid oral rabies vaccine.
Can oral rabies vaccine cause rabies?
Oral rabies vaccine does not contain the complete rabies virus and therefore cannot cause rabies. Researchers produced the oral rabies vaccinia virus such that it contains only a small fragment of genetic material from the rabies virus that leads to immunity against rabies.
How would I most likely come in contact with a bait containing oral rabies vaccine?
Human contacts with the liquid oral rabies vaccine are infrequent, even though millions of oral rabies vaccine doses have been distributed worldwide. During the spring and fall 2000 bait distributions, there were five reported instances of bait being found, however, there were no adverse effects. These reports indicated that most often pets located the bait and brought it to their owners.
Is oral rabies vaccine harmful to pets?
The oral rabies vaccine is one of the most extensively tested animal vaccines and is not harmful to pets. Studies on more than sixty species of animals, including domestic dog and cat, ferret, fox, gray squirrel, skunk, opossum, groundhog, horse, cow, pig, and sheep, have demonstrated its safety and effectiveness. A pet's intake of the oral rabies vaccine would likely only serve to boost its immunity. However, oral rabies vaccine is only approved for use in wildlife. State Law requires vaccination of dogs and cats against rabies by a veterinarian. For more information about rabies vaccination for your pet, call the Fairfax County Animal Shelter at 703-830-1100.
What if I find an oral rabies vaccine bait?
Baits should be left where found. However, if you find it necessary to relocate a bait, please toss it into brush or woods where it may be picked up by a raccoon. To avoid the odor of fish on your hands you should wear gloves and wash your hands with soap and water afterward. Use caution to avoid being bitten if removing a bait from your pet's mouth. Because the State-approved plan requires that we monitor contacts with oral rabies vaccine baits, you should report finding a bait by calling 703-246-8410. In the unlikely event that you come in contact with the liquid vaccine, you will be provided with additional information about the vaccine and be put in contact with a health professional.
If I still have concerns about the oral rabies vaccine, what can I do?
If you would like more information about any aspect of the oral rabies vaccine, you are welcome to contact the Fairfax County Oral Rabies Vaccine Pilot Program Manager, Dr. François Elvinger who may be reached at 540-231-7598 or written to at the following address:
Francois C. Elvinger
Dr.med.vet., Ph.D., Dipl.ACVPM
Associate Professor, Veterinary Epidemiology
Virginia-Maryland Regional College of Veterinary Medicine
Blacksburg, VA 24061-0442