Everything You Wanted to Know About Rabies

(But Were Afraid to Ask)

Back in February of 2007, the Center for Disease Control (CDC) issued this statement, “The United States is free of canine rabies.” So why do you still need to vaccinate your Beardie against rabies? It’s true that canine rabies has not been seen anywhere in the United States since 2004 according to an expert from the CDC, but this doesn’t mean your Beardie is safe from the rabies virus. For both humans and domestic animals, the four strains of rabies endemic in the United States within their named species are skunk, raccoon, bat and fox. All can cause disease in dogs, cats and humans. Currently, in the US, the number of cats infected with rabies has surpassed that of dogs (there are now more cats than dogs and cats tend to roam more, but stray cats seem to be at greater risk of infection than stray dogs). Rabies is a virus that can affect any warm-blooded animal; whenever a mammal is bitten by an animal, the chance of rabies exists. Although the incidence of rabies in humans is low, more than 30,000 people undergo treatment for possible exposure to rabies in the US each year.

What exactly is rabies? Rabies is a viral, zoonotic (an infectious disease that can be transmitted from animals, both wild and domestic, to humans, and often from humans to animals too) disease that causes acute polioencephalitis (inflammation of the gray matter of the brain) in mammals. The word "rabies" comes from a Latin word that means "to rage, madness, or fury" since the disease attacks the brain and the central nervous system causing bizarre, sometimes aggressive behavior. The virus, which is present in infected saliva, usually enters at the site of a bite. Saliva on an open wound or mucus membrane also constitutes exposure to rabies. The average incubation period is two to three weeks, but can also be as long as several months. The virus travels to the brain through the fluid in peripheral nerve fibers. The further the bite is from the brain, the longer the incubation period. Having spread through the central nervous system, the virus then spreads back out through sensory and motor nerves. The salivary glands in particular collect a large quantity of the virus and shed it in the animal’s saliva. The signs and symptoms of rabies are due to an inflammation of the brain known as encephalitis. There are three stages of the disease which are usually progressive. However, signs are variable, and atypical presentations seem to be the rule rather than the exception. In the first stage, called the prodromal, the signs are subtle and consist of personality changes. Affectionate and social pets may become aggressive and irritable. Shy pets may become overly affectionate. Other behavioral changes might include apprehension, nervousness/anxiety, biting, snapping, licking or chewing, biting at things, restlessness or excitability. Soon the animal becomes withdrawn and stares off into space. The eyes become sensitive to light, so the pet may seek seclusion and resist handling. Fever, vomiting and diarrhea are common.

The second stage is the furious stage; this is the “mad dog” type of rabies in which the animal becomes frenzied and viciously attacks anything that moves. The muscles of the face are in spasm, causing the lips to draw back and expose the teeth – rictus grin. As the throat muscles become involved there will be a change in the tone of the bark. The muscles become uncoordinated, the dog becomes disoriented and experiences seizures as it enters the final paralytic stage. As paralysis spreads, first the muscles of the head become affected causing the mouth to drop open and the tongue to hang out. The muscles that assist in swallowing are paralyzed, causing the animal to drool and paw at the mouth (this is the characteristic “foaming at the mouth”). As the encephalitis progresses, the animal loses control of its movement and eventually collapses.

There is only one way to positively diagnose rabies. The brain of the animal suspected of having rabies must be microscopically examined in a laboratory. Therefore, it is especially important that the head (brain) of an animal suspected of having rabies is not damaged when it is humanely killed. A rabies-vaccinated pet that bites someone or is suspected of rabies may be quarantined for 10 days instead of being humanely killed for rabies testing. Dogs and cats die within 10 days of showing clinical signs of the disease; therefore, animals that remain healthy throughout this period do not have rabies. The quarantine period is a precaution against the remote possibility that an animal may appear healthy, but actually be sick with rabies. From numerous studies conducted on rabid dogs, cats, and ferrets, we know that rabies virus inoculated into a muscle travels from the site of the inoculation to the brain by moving within nerves. The animal does not appear ill during this time, which is called the incubation period and which may last for weeks to months. A bite by the animal during the incubation period does not carry a risk of rabies because the virus is not in the saliva. Only late in the disease, after the virus has reached the brain and multiplied there to cause encephalitis does the virus move from the brain to the salivary glands and saliva. Also at this time, after the virus has multiplied in the brain, almost all animals begin to show the first signs of rabies. However, these signs can be mistaken for other illnesses. While all animals will show obvious signs of illness, even an untrained observer, within 3 to 5 days, unless there has been known exposure to a rabid animal the cause may be missed. Rabies should be considered as a possible cause of any encephalitis of unknown origin. Extreme caution must be used in handling any animal suspected of having rabies. Rule outs for these signs would be any brain disease or tumor, a head wound, laryngeal paralysis or choking.

Rabies was once rare in the United States outside the Southern states, but raccoons in the mid-Atlantic and northeast United States have been suffering from a rabies epidemic since the 1970s, which is now moving westwards into Ohio. Areas that are rabies free jurisdictions require dogs entering the area be quarantined to ensure the area remains rabies free. Import laws are designed to protect residents and their pets from potentially serious health problems associated with the introduction and spread of rabies. In many areas skunks are the most important vector in the transmission of rabies. Most human rabies is transmitted by bats. In many cases there was no evidence of a bite even when it was known a bat had been in the same room as the victim.

The first scientist to test rabies infection through the inoculation of saliva was a
German scientist named Zinke in 1804. Several other scientists followed in Zinke's footsteps, but it wasn't until Louis Pasteur began experimenting that a vaccine was developed. He became a worldwide leader in the development of vaccines, most notably for anthrax and rabies. Pasteur and his group of scientists began their work on the rabies vaccine by first injecting the disease into rabbits. They made various observations, including the amount of time it took for the virus to weaken in the spinal cords of the rabbits. In time, Pasteur began repeatedly injecting dogs with weakened versions of the virus and noted that injections could prevent the disease before exposure and afterward. The first treatment of a human patient was that of a young, badly bitten boy named Joseph Meister. The series of rabies vaccinations were a success; this was the beginning of the use of rabies vaccine throughout the world.

Over the last 100 years, rabies in the United States has changed dramatically. More than 90% of all animal cases reported annually to CDC now occur in wildlife; before 1960 the majority were in domestic animals. The principal rabies hosts today are wild carnivores and bats. Small rodents, rabbits, hares and possums rarely carry the disease, but woodchucks are more often infected. The number of rabies-related human deaths in the United States has declined from more than 100 annually at the turn of the century to one or two per year in the1990's. Modern day prophylaxis has proven nearly 100% successful. In the United States, human fatalities associated with rabies occur in people who fail to seek medical assistance, usually because they were unaware of their exposure. Rabies is rightly feared. By the time the symptoms appear, the disease can no longer be cured and almost always ends in death.

It is true the US is free of canine rabies, but we need to work to keep it that way. You still need to protect your pet from the rabies virus strains that are spread by wild animals. Speak to your vet about an appropriate vaccination schedule for your Beardie or ask your vet about a titer test (blood test to identify antibodies) to ensure your dog is adequately protected.

Maryann Szalka