Reducing the Risk of Rabies
By Linda Bren (staff writer for FDA Consumer)
A Suffolk, Va., couple didn't know they were being followed when they drove into their garage one evening in April 2005. When the man and woman got out of the car, they saw their stalker: a gray fox. The animal sprang at the woman, wrapped itself around her legs, and then tangled with the cat that came out of the house to greet its owners.
The fox was killed and found to have rabies. The woman, who had been scratched, received a series of rabies vaccinations and was fine. But sadly, the family cat was euthanized because it had not received its preventive rabies shot, says Calvin Jones, the environmental health manager for the Western Tidewater Health District in Virginia's Department of Health (VDH).
"The way we handled the case would have been different if the cat had a current rabies vaccination," says Jones, adding that the pet would have been revaccinated and confined for 45 days for observation. But to protect the public health, an unvaccinated pet exposed to rabies must be euthanized immediately or placed in strict isolation for six months with no direct human contact, says Jones.
Thanks to increased vaccination of pets and advances in human vaccines, the number of human deaths from rabies in the United States in the last century has decreased from 100 or more per year to an average of one to two per year, according to the Centers for Disease Control and Prevention (CDC). Yet rabid animals are found each year in every state except Hawaii.
In 2003, the CDC received reports of more than 7,000 cases of rabies in animals in the United States and Puerto Rico. More than 90 percent of the cases occurred in wild animals, mostly raccoons, skunks, bats, and foxes. Reports of domestic animals with rabies that year included 321 cats and 117 dogs.
Just three cases of rabies in humans were reported to the CDC in 2003, but more than 40,000 people may have been spared from the deadly disease by getting vaccinated after they were potentially exposed. The Food and Drug Administration has approved vaccines to prevent rabies in humans, and the U.S. Department of Agriculture (USDA) has licensed vaccines to prevent rabies in many animals.
"It's critical to keep current on rabies vaccinations to protect pets," says Suzanne Jenkins, V.M.D., M.P.H., epidemiologist and state public health veterinarian for Virginia, "and, more importantly, so they cannot transmit rabies to people."
If a person is exposed to rabies, "the sooner treatment is begun after exposure, the better," says Robin Levis, Ph.D., regulatory coordinator in the FDA's Office of Vaccines Research and Review.
Rabies is caused by a virus that attacks the brain. The virus enters the body through the saliva of an infected animal, usually by a bite, but it can also be transmitted if infected saliva gets into an open wound or splashes into mucous membranes such as those in the eyes, nose, or mouth. From the saliva's point of entry, the virus travels along nerve cells to the brain. It replicates there and moves to the salivary glands. In a rabid animal, the cycle is repeated when the animal bites a person or another animal.
Rabid animals may be aggressive and vicious, or lethargic and weak. In people, early rabies symptoms of fever, headache, and fatigue are followed by confusion, agitation, hallucination, and paralysis. Once symptoms begin, the disease is almost always fatal, says the CDC.
Only mammals get rabies--birds, reptiles, amphibians, and fish do not get the disease.
Human Rabies Vaccines
The FDA has approved several injectable products that are effective in preventing rabies in people who have been exposed to the virus. This post-exposure treatment consists of one injection of proteins that fight the infection (rabies immune globulin) and five injections of rabies vaccine over a 28-day period. The vaccine works by stimulating a person's immune system to produce antibodies that neutralize the virus. "The person develops a protective immune response before the virus reaches the brain and begins to actively replicate," says Levis.
Rabies immune globulin contains antibodies from blood donors who were given rabies vaccine. The antibodies provide interim protection until an exposed person's own antibodies develop in response to the vaccine. "In addition, injecting rabies immune globulin at the site of injury reduces the amount of virus that is able to enter the nerve cells and potentially initiate an active infection," says Levis.
No test can detect rabies in humans at the time of a bite. People who may have been exposed should immediately wash all bite wounds and scratches with soap and water to decrease the chance of infection. If the suspect animal cannot be captured and tested or observed for symptoms, the vaccine regimen should be started promptly. According to the CDC, no one in the United States has developed rabies when the currently recommended post-exposure treatment regimen was followed.
Rabies vaccine may also be given to people before they are exposed to the virus if they are considered at high risk for exposure, such as veterinarians, wildlife officers, animal handlers, and some laboratory workers. This pre-exposure regimen consists of three injections of vaccine instead of five. Being bitten by a rabid animal, though, requires two more vaccine injections. Pre-exposure vaccination simplifies therapy by eliminating the need for immune globulin and by decreasing the number of doses of vaccine needed after exposure, says Levis. It may protect people who unknowingly were exposed to rabies, as well as those who may be delayed in getting post-exposure vaccine, she says.
Before travel abroad, the CDC recommends consulting a health care provider, travel clinic, or health department about the risk of exposure to rabies and about ways to handle an exposure should it arise. A pre-exposure vaccine may be suggested when traveling to some developing countries or remote areas.
Older rabies vaccines required painful, daily injections in the abdomen for up to three weeks, and they could produce severe side effects, says Levis. Today's rabies vaccines require fewer injections, are given in the arm, and have few serious side effects.
Animal Rabies Vaccines
Rabies vaccines are available for dogs, cats, ferrets, horses, sheep, and cattle. To be effective, these vaccines must be injected before an animal is exposed to rabies. If exposed, the animal should get a booster shot.
"One of the most important ways to prevent rabies is to keep up to date on vaccinations for cats, dogs, and ferrets," says Jenkins. Depending on the type of vaccine used, it should be given yearly or every three years. Even indoor pets should have rabies vaccinations, Jenkins says, recalling a case in which a woman found her unvaccinated indoor cat with a bat in its mouth. The bat, which escaped, was assumed to have rabies, making for the tough decision of either euthanizing the cat or isolating it for six months.
Not only is it good preventive health care to vaccinate pets, but it's the law in most states for dogs and cats to be vaccinated against rabies, according to The Humane Society of the United States. Some states also require rabies vaccinations for ferrets.
In a cooperative program between the USDA, the CDC, and state governments, animals such as raccoons, coyotes, foxes, and skunks are being vaccinated orally in certain areas where rabid wildlife are frequently found. The oral vaccine is hidden in a bait of fish meal or other food. The baits are dropped by airplanes into rural areas and spread by hand in urban and suburban areas.
Keep Your Distance
Many more wild animals than pets are reported to have rabies, Jenkins says. But the most common reason people get post-exposure vaccines is that they're bitten by a domestic animal that isn't available for testing. "They may see a cute dog or cat on the street that they try to pet, and it bites them and runs off," she says.
"Avoid wildlife and domestic animals that you don't know," advises Jenkins. Most healthy wild animals will generally try to avoid humans, she says, but wild animals at parks and camp sites may be more brazen if they're used to getting handouts.
If you're hiking in a remote area "and a raccoon is sitting in the middle of a path and doesn't want to move, I'd take a very wide path around it," says Jenkins.
Wildlife are not found only in remote or rural areas, says Mark Dembert, M.D., M.P.H., district director of the VDH's Western Tidewater Health District. Dembert says that new development disturbs wildlife habitats and wildlife become more visible. "People encroaching on nature is a factor in a lot of places," he says. "Rabies is becoming more of a suburban problem."
Dembert advises people who are planning a move or a vacation with their pets to call ahead and ask the health department whether rabies is a problem in the area. Vaccinate and be vigilant, he says. "It just makes good sense if you have pets. It can ruin a family's summer vacation if a skunk comes in and bites Fido at your vacation rental."
Rare Recovery From Rabies
Only one person in the United States is known to have recovered from rabies without receiving a rabies vaccination, according to the Centers for Disease Control and Prevention. While attending a church service in September 2004, 15-year-old Jeanna Giese of Fond du Lac, Wis., picked up a bat she saw fall to the floor and released it outside the building. The bat bit her on the left index finger, but she did not get medical treatment at the time. A month later, the teen complained of tiredness and a feeling of numbness in her left hand. Walking became difficult, and she experienced double vision, nausea, vomiting, slurred speech, twitching, and fever. Giese was diagnosed with rabies and after intensive care in a Milwaukee hospital, which included a drug-induced coma for seven days, she gradually improved. Doctors are unsure whether she will fully recover.
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