What is rabies and what causes it?
Rabies is an infectious disease that spreads from animals to humans. The rabies virus causes the disease by infecting nerves in animals and people. The rabies virus travels to the brain (through nerves inside the brain), the virus reproduces, and then it travels back through the nerves to most parts of the body. Eventually, the virus reaches the salivary glands where it is released into the saliva in the mouth. By this time, the disease has usually damaged the brain, sometimes producing violent behaviour. It eventually causes death.
How long does it take for rabies to develop?
In people, the incubation period (the time between initial contact with the virus and onset of the disease) generally ranges from two to eight weeks. In rare cases, it can vary from 10 days to 2 years. The incubation period is shorter in children and in people exposed to a large dose of the rabies virus. The dose of virus depends on the size, severity and location of an animal bite or scratch. In animals, the incubation period depends on the species of animal. For dogs it normally ranges between 14 and 60 days, but it can be much longer.
What is the source of rabies?
The major risk of rabies comes from contact with the saliva, body fluids, or tissue of infected animals. Animals that can be infected with rabies include all mammals, but in particular:
- wild animals--mostly foxes, skunks, bats, and raccoons
- livestock--mostly cattle but occasionally horses, sheep, goats, and pigs
- pets--mostly cats and dogs, and occasionally ferrets
In Canada, rabies is also found in wolves, coyotes and other meat-eating animals. It is rarely found in rodents such as mice, squirrels, chipmunks, groundhogs, rabbits, rats, hamsters, or gerbils, so their bites do not usually pose a risk for rabies.
How common is rabies in Canada?
Since reporting began in 1924, 24 people have died in Canada from rabies. More recently, one person died in 2007 (Alberta), another in 2003 (British Columbia) and another in 2000 (Quebec). However, rabies has become well established in Canadian wildlife and increased steadily up to the year 2000. Since 2000, positive rabies in animals has declined steadily from 670 to 145 cases in 2009. Thirty percent (30%) of all confirmed rabies cases occur in bats and skunks in Ontario, Manitoba and Saskatchewan.
In recent years, most reported wildlife infections in British Columbia and Alberta have been in bats; in Saskatchewan and Manitoba, in skunks; in Ontario in bats and skunks; in Quebec, in raccoons and skunks and in the Northwest Territories, in foxes. Rabies has been reported in Newfoundland/Labrador in foxes up to 2005, and sporadically from New Brunswick, in bats.
In domestic animals, rabies is most commonly found in cattle and represents about 5 to 11 % of total confirmed rabies since 2004. Dogs and cats each account for about 2 to 6% and 1 to 2.5% respectively. About 60 percent of human exposure to rabies occurs because of group contact with rabid dogs or cats.
How do rabies infections occur?
To cause an infection, the rabies virus must enter the body and reach nerve cells. The virus can enter the body through broken skin. Droplets containing the virus can pass through mucous membranes in the eyes, nose, mouth, or intestine. Usually, transmission occurs when rabid animals, with the virus in their saliva, bite people. Farmers or veterinarians can become infected when they work with their hands in the mouths of rabid cows which often appear to be choking on food. Laboratory workers have also contracted rabies from cuts or sticks from contaminated needles, scalpels or other contaminated laboratory equipment.
In unusual situations, workers have contracted rabies by breathing air that carried high concentrations of the virus. This phenomenon has occurred in bat caves. It has also happened in the laboratory where improper procedures produced a mist or aerosol containing the virus. Contact with the blood, urine or manure of a rabid animal is not a risk factor for contracting rabies.
The virus can become inactive, but the rate at this occurs depends on moisture, sunlight and temperature. The rabies virus is not infectious if it has dried out or exposed to sunlight.
What occupations have increased risk of rabies?
Rabies is an occupational risk for people who work with wild animals, livestock, or pets.
- exposure to wild animals--hunters, trappers, forestry personnel, wildlife biologists, forest rangers, conservation officers, taxidermists, veterinarians and their assistants, zoo personnel, and scientists working in caves
- exposure to livestock--farmers, farm workers, ranchers, veterinarians and their assistants, artificial insemination technicians, laboratory animal researchers and technicians, slaughterhouse workers, and meat packers and processors.
- exposure to pets--veterinarians and their assistants, pet groomers, letter carriers, meter readers, delivery personnel, laboratory animal researchers and technicians, animal control officers, and hunters.
How do you recognize rabies?
Workers who may have been exposed to rabies must never wait until they develop signs of the disease. Once the signs appear, the disease is almost inevitably fatal within weeks of symptoms appearing, if not treated.
It is important to recognize the signs of rabies in animals and take precautions immediately following bites, scratches, or other potentially infectious contact.
In people, rabies progresses through several stages. Initially, a person who is bitten may notice unusual feelings or tingling around the wound. Soon afterwards, there is a period of tiredness, possibly with lack of appetite, headache, fever, cough, sore throat, abdominal pain, nausea, vomiting, and diarrhea. A period of extreme worry, irritability, inability to sleep, and depression follows, possibly with hallucinations. "Furious rabies" may follow, for which the signs are strange behaviour including biting other people. At this stage, victims have an uncontrollable fear of water. This is why rabies has sometimes been called "Hydrophobia." Sometimes "paralytic rabies" develops instead of furious rabies. With this form of the disease, the muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops, and eventually death occurs.
In animals, rabies appears in two different forms. It may appear as furious rabies in which the animal changes behaviour, becomes restless, wanders aimlessly, and bites any animal, person, or object in its way. Eventually the animal becomes paralyzed in the throat and hind legs, and dies. Or it may appear as "dumb rabies" in which an animal changes behaviour, becomes withdrawn or more affectionate, tries to hide, has difficulty swallowing, and dies after a few days without ever becoming violent.
All animals do not behave in the same manner when they have rabies.
- Foxes and skunks may lose their shyness and fear of people, pets, or livestock.
- Cattle usually become restless and aggressive, bellow loudly, drool, may show gradual weakness in the hind legs, and appear to be choking.
- Cats can often become extremely vicious.
- Dogs usually become excitable, and may be vicious, wander aimlessly, and bite for no reason.
Any animal exhibiting unusual behaviour should be considered a potential rabies hazard for humans.
What laboratory tests are available for rabies?
Laboratory tests are available to detect the rabies virus as well as specific antibodies. The body produces antibodies to protect itself against the disease. Tests for rabies antibodies are occasionally ordered to determine if people have been successfully immunized against the disease.
Doctors usually do not test people to see if they have been infected with the rabies virus. Reliable test results are usually not obtained until the disease has progressed to an advanced stage. Instead, doctors generally rely on tests of suspect animals to determine if a person has been exposed to the virus.
Federal government laboratories can perform several different tests on animals. The most important test involves examining the brain for the presence of the virus or for specific changes caused by the rabies virus. Because of this, it is important to avoid damaging the brain when killing an animal suspected of having rabies.
What is the treatment for rabies?
There is no successful treatment for rabies once the disease has progressed to the point where signs appear. Only three patients in medical history have survived the disease after it progressed to this stage. Medical treatment can sometimes extend life but the disease eventually ends in death. It is very important to stop the disease from developing in people who may have been exposed to the rabies virus.
How can workers be protected from rabies?
All workers at potential risk of contracting rabies should be informed about the disease, its characteristics, and the nature of the risk.
Agricultural, public health, veterinarian, and occupational health officials share the responsibility to control rabies in animals and to protect people.
Vaccination programs, established to immunize dogs and cats, have been effective in reducing rabies in pets. However, rabies will continue to be a threat until the virus can be eliminated from the wild animals that spread the virus to pets and people. Research programs for this solution are in progress. For current programs to be successful, people must continue to be well-informed, alert, and cooperative.
Some workers such as veterinarians or animal control officers have continuing risk of encountering a rabid animal. These workers should be immunized to ensure that they have protection before having contact with any animal. For other workers much less likely to encounter rabid animals, it might be sufficient to provide education on the risks, and training on protection if they encounter an animal with rabies.
Specific recommendations depend on the individual situation. The following general recommendations apply to all workers who risk contacting rabid animals.
Preventive measures include:
- proper precautions for dealing with rabid animals and the possibility of contacting the rabies virus
- immunization of workers either before or immediately after exposure to the virus
- workplace hygiene
What precautions are required to control rabies?
Workers who have contact with animals must know how to deal with rabid animals and how to protect themselves from the rabies virus.
Dealing with rabid animals
Do not approach or kill an animal suspected of having rabies except to defend yourself, other people, or other animals. If an animal must be killed, try to avoid damaging its head. An undamaged brain is important for a quick laboratory diagnosis. If an animal suspected of having rabies is responsive or manageable, keep it alive and away from other animals or people. Do not touch it with bare hands. If an animal is unmanageable and dangerous and cannot be restrained or killed, observe its movements and seek help from qualified experts as soon as possible. If you must handle the animal or carcass, wear protective gloves to prevent infectious material from having contact with cuts or rashes on the skin. Also wear protective masks and goggles to protect against infectious aerosols. When there is a need for personal protective equipment (PPE), then there should be a PPE program in place where you work.
According to Canadian federal regulations, all pets, livestock or wild animals suspected of being rabid, or suspected of being in contact with an animal that might have been rabid, must be reported without delay to the local district office of the Canadian Food Inspection Agency. The phone number of each federal district office is listed in the telephone book under Government of Canada. In an emergency, sightings of rabid animals should be reported to local veterinarians, humane society officials, municipal animal control officials, or police.
Government veterinarians are familiar with the federal regulations concerning rabies and, if necessary, will collect and ship specimens to a federal laboratory for analysis.
Protection for workers who have had contact with the rabies virus
Workers who have come into contact with saliva, body fluids, or tissue of animals suspected of having rabies must take the following steps without delay.
Immediately clean and flush the wound to full depth with water for several minutes. This will help wash out the virus. If available, use soap or detergent to help kill the virus. Washing the wound is probably the most effective procedure in the prevention of rabies. While this is being done, shield the eyes, nose, and mouth from spray from the wound.
After cleaning the wound and removing all traces of soap, apply a household antiseptic, 70 percent alcohol (ethanol), tincture or aqueous solution of iodine, or 0.1 percent quaternary ammonium compound such as benzalkonium chloride.
Remove any clothing that may be contaminated, place it in a plastic bag properly labelled and wash it promptly and separately from other clothing. Call a doctor or emergency department of a hospital.
Contact the police, your local health unit and district veterinarian or local office of the Canadian Food Inspection Agency. If possible, provide the following information:
- the name and address of all persons attacked or exposed to the animal's saliva, body fluids or tissues
- the time and place of the incident
- any other information to help find and identify the offending animal
Laboratory precautions for rabies
Biosafety containment level 3 is recommended when working with the rabies virus (includes full coverage protective clothing, front gowns with tight fitting wrists, gloves, respiratory protection, and eye protection (if risk of splashes)). Additional precautions may be necessary. Please see the Rabies Virus - Pathogen Safety Data Sheet (2011) from the Public Health Agency of Canada for more information.
What kind of immunization is available for workers?
There are two types of immunization:
1) Active Immunization
People who require immunization before exposure to the virus need three doses of the rabies vaccine (human diploid cell vaccine - HDCV or purified chick embryo cell vaccine - PCECV), one dose each on days 0, 7, and 21. People who require immunization after contact with the virus need five doses. The first injection should be given as soon as possible and the rest on days 3, 7, 14, and 28. The vaccine provides protection starting 7-10 days after injection and lasting for over a year. The vaccine sometimes causes local reactions at the injection site but rarely severe reactions.
2) Passive Immunization
The rabies immune globulin (RabIg) which contains antibodies that neutralize the virus provides rapid protection but lasts for only a few weeks. It is given in one dose directly into the wound as soon as possible after contact. Such wounds should not be sutured. Vaccine (HDCV) and immune globulin (RabIg) should be used concurrently to help develop active immunity.
Immunizing before contact
In Canada, the National Advisory Committee on Immunization recommends that pre-exposure rabies vaccination should be offered as a choice to workers at possible high risk of contacting rabid animals. These workers include veterinarians, animal handlers, certain laboratory workers dealing with rabies, workers who have contact with bats or bat caves, forest rangers, conservation officers, wildlife biologists, and certain travellers at high risk. About 35% of the annual doses are used for pre-exposure vaccination.
Workers with continuing high risk should have their blood tested every two years to determine if booster injections are required. Laboratory workers who could have accidental contact with the rabies virus without knowing it should be tested every six months. Those with inadequate levels of antibodies should be given a booster dose of vaccine.
Immunizing after contact
People who have had contact with the rabies virus require both the rabies immune globulin (RabIg) and the rabies vaccine (HDCV or PCECV) as soon as possible. About 65% of the annual doses are used for after contact vaccination.
Only a single dose of rabies immune globulin is necessary. In previously vaccinated people, only two doses of the vaccine are required after a biting incident, one immediately and another three days later.
Immunization may be considered after contact in the following situations:
- The animal appeared to have rabies.
- The animal may possibly have had rabies.
- The animal was wild, from a region where rabies is known to be a problem.
- The animal was a dog or cat that escaped after the contact without being tested.
Immunization is usually recommended if the animal makes contact by biting, or if the animal's saliva, body fluid or tissue makes contact with a rash, scratch, open wound, eyes, nose, or mouth.
Wild animals or unwanted dogs or cats suspected of having rabies are humanely killed without delay. Their heads are submitted for laboratory examination. Vaccination may be discontinued if tests of animals killed at the time of attack are negative.
Medical professionals generally do not recommend immunization if the animal had no contact with a person's skin or mucous membranes. Nor is immunization recommended if workers have had only casual contact with the animal such as petting, with no possible contamination of broken skin or mucous membranes.
Healthy dogs or cats involved in biting incidents are held in confinement for at least 10-14 days, according to provincial regulations. If rabies does not develop in that time, no immunization is required for the injured worker. If signs of rabies do develop, the Canadian Food Inspection Agency should be notified, the animal humanely killed and analyzed; and immunization started without delay.
What is recommended for workplace hygiene?
Develop procedures to prevent contact with the rabies virus within the workplace. Where appropriate, have workplace procedures posted for disinfecting or sterilizing areas that may be contaminated with the rabies virus.
Quarantine all wild animals prior to introducing them into an animal research program. Avoid using animals obtained from a pound in research studies.
Use caution if handling animals killed by the roadside since they may have had rabies.
Wear protective face masks, gloves, clothes, and shoes when handling anything from an animal suspected to have rabies or when cleaning areas where suspected rabid animals are confined.
The rabies virus does not survive long outside of animals. It is generally destroyed by heat, sunlight, or air. Detergent, ethyl alcohol, or a one-in-ten dilution of household bleach can also destroy the rabies virus.
Routinely disinfect working surfaces, tools and instruments, floors and walls that may have been contaminated with fluids from animals, using procedures established for infection control.
Use ultraviolet light for disinfecting areas such as laboratories where the rabies virus may become airborne. These lamps must only be used during nights or weekends when no workers are in the workplace.
Package infected waste in puncture-proof, leakproof containers. Clearly label and sterilize them before disposal according to procedures developed for biological hazards.
Although every effort is made to ensure the accuracy, currency and completeness of the information, CCOHS does not guarantee, warrant, represent or undertake that the information provided is correct, accurate or current. CCOHS is not liable for any loss, claim, or demand arising directly or indirectly from any use or reliance upon the information.