by Whit Gibbons

April 3, 2011

I've received the following questions about rabies.

Q. We watched a raccoon climb a tree in our backyard one afternoon. We approached and it just sat there, seemingly unafraid, on a limb five feet above the ground. It started drooling and growling, so we backed away. Later that week we found a dead raccoon in the backyard. Could the animal have had rabies?

A. It very likely did have rabies, and leaving it alone was certainly the right thing to do. Several aspects of its behavior are telling. First, it was out in the middle of the day: Raccoons are usually nocturnal. Second, it let you get close. Third, it was drooling, not something we want to see in a raccoon, one of the most prevalent reservoirs for rabies. It probably died because it was infected with the rabies virus.

According to information received later from the same county, animal control picked up two more strange-acting raccoons that were found to have rabies. Incidental cases of rabies among wild mammals are not that unusual in many parts of the country and are certainly no cause for alarm. Knowing about the disease can help people avoid problems for themselves and for domestic dogs and cats, all of which are susceptible to infection by the rabies virus.

Q. What animals transmit rabies?

A. Any warm-blooded animal can harbor the virus. According to the Centers for Disease Control the most common US wildlife species to be infected are foxes, skunks, raccoons and bats. Unvaccinated domestic pets are also susceptible, as are coyotes, which have become more prevalent in the Southeast in the past two decades. The CDC notes that small mammals, including "squirrels, rats, mice, hamsters, guinea pigs, gerbils, chipmunks, rabbits, and hares are almost never found to be infected with rabies." They are not known to have caused rabies in humans in the United States. One odd statistic is that the woodchuck (aka, groundhog), has a high incidence of the disease. According to some scientists, possums supposedly do not get rabies, although they will certainly bite if given an opportunity.

The rabies virus is usually introduced by saliva during biting; rarely, it can enter the body through mucous membranes. The virus multiplies in the nervous system, and symptoms usually develop within three months, but occasionally can appear in only a few days. Rabies victims have difficulty swallowing water, because of paralysis of the throat muscles. The seeming aversion to water led to the name "hydrophobia," which means fear of water. The loss of muscular control of the throat muscles can also result in excessive drooling, leading to the "foaming at the mouth" symptom.

The first line of safety precautions for dealing with rabies is pretty much common sense. Don't pick up a drooling, growling raccoon (in fact, don't pick up any wild raccoon). Likewise for sick or injured bats. Bats are beautiful animals in flight, especially when they are eating mosquitoes, but if you find one on the ground or in a house, don't let it bite you. CDC records indicate that rabies has been documented in bats from all 48 of the conterminous states. All domestic dogs and cats should be vaccinated, especially those likely to go outside or come in contact with wild animals.

Q. I have heard some people suggest that we should start vaccinating wild animals to prevent rabies epidemics. Is this feasible?

A. Such a plan would be costly--and it's unnecessary. Wild animals are not the problem if we avoid situations in which we are likely to get bitten. CDC records show that "control of dog rabies through programs of animal vaccination . . . reduces the incidence of human rabies." Rabid dogs are the cause of more than 90% of human infections of the rabies virus and the source of more than 99% of human deaths from rabies worldwide.

We should have our pets vaccinated at a vet's or a rabies clinic, but let's leave the wild animals to take care of themselves.

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