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    Infectious Disease Control Unit
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Facts about Rabies

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image Rabies
(Lyssa)
ICD-9 071; ICD-10 A82
Related Topics: Oral Rabies Vaccine Programs

Each year many cases of rabies develop among Texas wildlife and domestic animals. Rabies is a disease of overpopulation. It thrives where there is an abundance of wildlife, as there is in most counties in Texas.

It is possible to control this disease. People in several foreign countries and in some of our own states have, by working closely with their health and wildlife authorities, eliminated rabies as a threat to both animal and human life.

The more we understand about an enemy, the easier it is to overcome. That is the purpose of this pamphlet - to impress upon the reader what rabies is and is not so he or she can help control it.

Historical Fact and Fiction

Rabies - sometimes called "hydrophobia" - has its roots in antiquity. Centuries before the birth of Christ, it was recognized in both animals and man. Cases were described with amazing clinical accuracy during the lifetime of Aristotle. The name hydrophobia, meaning "fear of water," was given to it at that time because the ancient Greeks observed rabid animals' aversion to water. Actually, the truth is that they cannot drink because of throat paralysis. It is this fact which produces the classic picture of a beast with foam-flecked jaws. Saliva accumulates in the paralyzed throat and drools from the corners of the mouth, giving the impression of mad-dog foam. Certainly it isn't hard to understand why those ancient people were terror stricken by such a sight, and even thought the animal was demon-possessed. Writers of the day attributed rabies to an invasion of the body by a evil spirit.

Through the years, a wall of superstition was built. The wall has never been completely torn down. Even today, many people believe that the bite of a civet cat (or "hydrophobia cat"), a small spotted skunk, invariably leads to rabies. Actually, while all skunks are susceptible to rabies, laboratory studies have proved it is wrong to assume all civet cats are rabid.

What Is Rabies?

Rabies is a virus disease of the central nervous system. It can be transmitted by the bite of a rabid animal, or through the saliva of a rabid animal being introduced into a fresh scratch or similar skin break, and rarely by other routes. Saliva in contact with unbroken skin - or even on a scratch wound over 24 hours old, one where a scab has formed-usually will not require anti-rabies treatment. You should definitely see a doctor if you think the animal could be rabid.

Where is Rabies Found?

At one time or another, rabies has occurred in almost every part of the world. An exception is Australia, where a case has never been diagnosed.

Some countries once affected have eliminated rabies entirely by stringent control and enforcement measures. Denmark, Sweden, Norway, Hawaii, and the British isles have been free of the disease for many years. Although it had been completely eliminated from England prior to World War 1, it was reintroduced and had to be reeradicated. Currently, rabies is probably most prevalent in Russia, Belgium, France, the United States, Africa, Mexico and the lower Americas.

In some sections of the United States, rabies is extremely rare.

When a Known Rabid Animal Bites a Dog or Cat

Unvaccinated dogs and cats bitten by a known rabid animal should be destroyed immediately. If the owner is unwilling to have this done, the animal should be vaccinated and placed in strict isolation for 90 days and given booster vaccinations during the third and eighth weeks of isolation. If the animal is currently vaccinated, it should be revaccinated immediately and restrained (leashing and confinement) for 45 days.

When Is Rabies Most Common?

Contrary to popular belief, rabies is not confined to the so-called "dogdays" of July and August. Most cases in Texas occur in the spring, probably because there are more opportunities for transmissions during the spring mating seasons of wild carnivores. Rabies does occur through the entire year in Texas in both wild and domestic animals. Rabies in bats occurs mostly in the warmer months.

What Animals Get Rabies?

All warm-blooded animals, including humans, are susceptible to rabies. In Texas, skunks, bats, coyotes, and foxes are the most commonly infected animals. This does not mean that wildlife eradication campaigns should be started. Wild species are highly beneficial in keeping pests under control, but it is wise to realize that they can carry rabies, and that contact with them should be avoided at all times-especially with those which are obviously sick.

Domestic dogs, cats, and livestock usually acquire rabies infections from wild animals; while the numbers of rabid domestic animals are fewer, their danger is greater because of their close association with humans.

How Is Rabies Spread?

A common distribution pattern is for a rabid skunk or fox to bite and infect one or more dogs or cats during a fearless invasion into a community. The disease develops in the domestic animals along with the threat of their transferring the infection to other pets and perhaps humans. Children-because of their closer association with the pets- are most often the human victims. This rapid spread is possible only in unvaccinated pets.

If an infected fox or skunk gets into a barnyard, it may bite and infect the farm dog, cat or other livestock.

As a matter of interest, a fox can be 20 times as serious a distributing agent as a skunk since it travels faster and farther; skunks however, have more rabies virus in their saliva.

Clinical Course of Rabies Infection

The course of the disease is divided into three states: 1st - incubation period; 2nd - clinical signs; and 3rd - paralysis terminating in death.

The incubation period is the time it takes clinical signs to develop after exposure to a rabid animal. It takes from 14 days up to 18 months for rabies to incubate, depending on the animal species, the amount and virulence of the virus, the age of the victim, and the site of the wound.

The average incubation period, which varies greatly, is 3-8 weeks for most species.

Medical authorities distinguish on the basis of clinical signs, between "furious" and "dumb" rabies. In the furious variety, the "mad dog" symptoms are pronounced. The animal is irritable and will snap and bite at real or imaginary objects. It may run for miles and attack anything in its path. The animal is extremely vicious and violent. Paralysis sets in shortly, usually affecting the hind legs first. Death follows four to seven days after the onset of clinical signs.

In dumb rabies, the prominent symptoms are drowsiness and paralysis of the lower jaw. The animal may appear to have a bone lodged in its throat, sometimes causing owners to force open an animal's mouth to investigate and become unwittingly exposed to rabies.

Animals with dumb rabies have no tendency to roam but will snap at movement. They are completely insensitive to pain, and usually become comatose and die from three to ten days after first symptoms appear.

Pasteur's Anti-Rabies Treatment

Although rabies has plagued both man and animals from the dawn of recorded history, it was not until 1884 that Louis Pasteur, the great French bacteriologist, first announced his discovery of an anti-rabies vaccine. There is a fascinating story behind the discovery.

During Pasteur's time, France was overrun with rabies and Pasteur's research stemmed from a great humanitarian soul and a zealous desire to do something to mitigate the horrible, inevitable fate of rabies victims. Once in the village of Arbois where he lived, he saw one of the townsmen being treated for a wolf bite by having the wound cauterized with a red hot iron. That was the only treatment method known then, and he never forgot the sight.

Pasteur was never able to isolate the virus which caused the disease, but he did develop a vaccine against it. He took some saliva from a rabid dog and injected it into a rabbit, which subsequently died. Pasteur then removed its spinal cord and allowed it to dry for 14 days. He reasoned that drying the spinal cord would weaken its virus content to the point it wouldn't cause disease when injected into a human body, but would still trigger the body's natural defense mechanism to produce rabies antibodies.

He used this vaccine to inoculate a small boy, despite his own misgivings and a loud howl of protest from the public. Joseph Meister, a little Alsatian boy, had been severely bitten by a mad dog. His mother turned to Pasteur as a last hope. First, the scientist injected the lad with the 14-day-old preparation, and gradually day by day increased the virulence of the vaccine until he was using a 3-day-old solution-that is, the spinal cord of the rabbit from which the emulsion had been compounded had been allowed to dry for only three days. Joseph Meister did not develop rabies and the world had its first weapon against the disease,

The Danger of Treatment

Formerly, hazards connected with taking anti-rabies treatment were considerable; however, the rabies vaccine and antiserum in current use have excellent safety records. Since the chances of developing the disease are so much greater than the chances of adverse reaction to the vaccine, anti-rabies treatment should be administered in all cases of known or uncertain exposure.

When an Animal Bites a Person...

Any time a warm-blooded animal-a dog, fox, skunk, cat, bat, etc.-bites a human being there is a danger that the animal is rabid and that the person involved may in turn develop rabies. Immediate precautions should be taken:

Identify and, whenever possible, confine the biting dog or cat for observation or submit the animal's head for laboratory examination.

Wash the wound thoroughly with soap and hot water as an immediate first aid procedure. Consult a physician as soon as possible concerning the advisability of anti-rabies treatment.

The owned dog or cat need not be euthanized (humanely killed) until the first clinical sign of rabies appears. if the dog or cat was infective at the time of the bite, signs of rabies in the animal will usually follow rather quickly and certainly within 10 days. Rabid dogs and cats usually show a change in behavior, with excitability or paralysis, followed by death. However, the biting animal can be euthanized immediately. Note: Do not mutilate or destroy the BRAIN. If the animal was infective at the time of the bite, the fluorescent antibody test will confirm the presence of rabies virus.

Wild animals involved in attacks on humans should be euthanized immediately and the brain examined for evidence of rabies. They should never be quarantined.

If symptoms of rabies appear in an animal confined for observation, immediately notify the physician who was consulted at the time of the attack, and call a competent veterinarian or the State Health Department. The physician will decide whether to begin the anti-rabies treatment at once, and the veterinarian will verify the animal's rabid appearance and later prepare the animal's head for laboratory examination.

How the Laboratory Diagnoses Rabies

Today's laboratory technicians have a rapid and sophisticated diagnostic tool available to them. It is the "fluorescent antibody test" and has replaced the Negri body method of diagnosis. If rabies virus is present, it can be quickly and accurately detected with the flourescent antibody technique.

The Control of Rabies

Effective community control of rabies is possible. The first step in such control is an informed and cooperative public. Public education as to the problem and the solution is essential.

Community control of rabies can be accomplished by the following measures:

Immunization of all owned dogs and cats: All dogs and cats over 4 months old should be vaccinated against rabies. Vaccination should be obtained through private veterinarians or in community-sponsored vaccination clinics.

Registration and licensing of all owned dogs: In a properly enforced program, licensing revenues can help pay for community anti-rabies activities. Such a program helps provide a dog and cat census, and places control responsibility where it rightfully belongs-on pet owners.

Impoundment and elimination of all stray dogs: This program requires suitable impoundment quarters, and facilities for the humane destruction of unwanted animals. Trained animal control personnel are also necessary.

Quarantine of rabies suspects: Dogs and cats involved in biting incidents or which are suspected ofbeing rabid should be confined in isolation under veterinary supervision for at least 10 days. Unowned dogs and cats may be killed immediately for testing. If the virus is present in the saliva, the brain will be positive by the fluorescent antibody test. No biting wild animal should be held in quarantine. They should be humanely killed and tested immediately.

Directions For Shipping Heads To The Laboratory For Rabies Diagnosis

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Last updated March 28, 2011
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