RABIES (LA RAGE)
Rabies (La Rage) is a virus disease normally transmitted in the bite of mammals. Any mammal is susceptible to rabies although some are more susceptible than others. In Ontario, red fox and striped skunk are the most commonly infected wildlife which spread the disease to domestic animals and man (see Table 1). Vertebrates such as birds, reptiles, amphibians, and fish are not normally infected in the wild.
Transmission and Symptoms
In Ontario, the annual peak of rabies activity is in the fall and winter with less transmission during the summer. In the spring humans are often exposed to rabies when they catch young wild animals such as foxes or raccoons and take them home for pets. Although rabies may be present at any time or place in the province, it is primarily endemic in southern Ontario. Periodic cycles with peaks every 3 to 4 years correspond to high fox populations.
In attempting to control rabies in wildlife in Ontario the OMNR in cooperation with other provincial ministries and Connaught Laboratories Ltd. is developing an oral rabies vaccine. It will be incorporated into a bait for vaccinating foxes, skunks, etc. in the wild. Aircraft will deliver the bait to remote areas. It is hoped that this method will result in reduction of rabies in wildlife.
There are 2 distinct periods in the development of rabies following the entry of virus through the bite wound. These are the incubation period and the symptomatic period. During the incubation period, which varies from 2 weeks to I year, the virus multiplies in the area of the bite wound and moves to the brain.
The symptomatic period usually lasts 3-5 days during which abnormal behaviour and biting occur. The animal's saliva is considered to be infective only a few days prior to, and during, the symptomatic period. At the end of this period the animal succumbs to convulsions and paralytic seizures.
Rabies should be suspected in any mammal displaying abnormal behaviour such as loss of fear of man or normal animal enemies; aggression; attacks and biting; eating non-food items such as soil, stones, sticks, faeces; loss of balance; convulsions and paralysis. In domestic pets a change in temperament or normal habits may be an early sign of rabies.
Red foxes lose fear of man and other animals and may attack without provocation. They are attracted to strong scents such as mammal faeces and farm manure. The presence of porcupine quills in the muzzle or skunk scent on the fur are certain indicators of rabies in red foxes.
Skunks, like foxes, usually try to avoid man and other animals but when rabid may be unafraid, bite without provocation, and often do not spray their scent. Skunks wandering about aimlessly during the daytime should be suspected although uninfected skunks may also be seen during daylight in the mating season of late winter and early spring.
The big brown bat is the most important of 5 species of Ontario bats from which the rabies virus has been isolated. Suspect bats may be found flying in daylight or fluttering on the ground where their squeaks attract domestic pets and other animals which can be bitten on the lip or muzzle. Aerosol transmission of rabies is known to occur in bat caves in the United States but has not been reported in Ontario.
Raccoons are not as commonly infected with rabies as foxes or skunks in Ontario, and are more often infected with canine distemper virus than with rabies virus. Raccoons with either disease are frequently found wandering aimlessly or sitting inactive in the open and may be aggressive when approached. Therefore, a sick raccoon should be considered rabid until proven otherwise by lab diagnosis.
Rabid timber wolves and coyotes display symptoms similar to foxes and because of their size can be extremely dangerous.
Handling of Rabies Suspect Cases
Extreme caution is imperative when handling any mammal suspected of being rabid. They can be aggressive and bite even when apparently paralysed. Species such as woodchuck and muskrat which are not usually considered aggressive can also attack when rabid and inflict dangerous wounds.
Suspected rabid wildlife should be shot in order to limit further spread of rabies and to obtain a specimen for diagnosis in cases where humans and domestic animals have been exposed. If feasible, the animal should be shot in the chest so that the head is available for microscopic diagnosis.
Gloves or similar protection should be worn when handling suspected rabid carcasses to avoid contact between the animal and your skin, eyes, nose, and mouth. The specimen should be placed in a double plastic bag of heavy thickness and then in a metal container such as a pail or garbage can. It should be kept cool either by refrigeration or freezing and be isolated from children and household pets until submitted. The area and materials contaminated by the carcass should be decontaminated by washing with a disinfectant such as household bleach or by incineration.
Specimens suspected of being rabid should be submitted immediately to the Health of Animals Branch, Canada Department of Agriculture for diagnosis. In addition to information requested under "Submission of Specimens", the names, addresses and particularly phone numbers of any persons or domestic animals exposed to the rabies suspect animal should be submitted.
Pre- and Post-exposure Medical Treatment
In addition to bites the following forms of exposure to potentially rabid animals warrant medical attention: licks or saliva contact with skin, eyes, nose, lips, cuts or scratches.
Since elimination of rabies virus at the site of infection by chemical or physical means is the most effective mechanism of protection, immediately wash and flush with soap and water, detergent, or water alone. After washing, apply either 40-70% alcohol, tincture or aqueous solutions of iodine, or 0.1% quaternary ammonium compounds.
Immediately following first-aid treatment the patient should contact a physician or a hospital emergency ward. Rabies vaccine and antiserum will be administered as required. Expert consultation on human rabies exposure can be obtained by physicians from the Ontario Ministry of Health, Toronto, Canada.
Pre-exposure vaccination is available for high-risk personnel such as conservation officers, resource and animal care technicians, trappers, spelunkers, veterinarians, and wildlife biologists. New safe vaccines are available which will provide initial protection should a subsequent exposure occur. Information on pre-exposure procedure is available through the Rabies Unit, Wildlife Research Section, Wildlife Branch, Ministry of Natural Resources, Maple, Ontario or the Epidemiology Section, Ministry of Health, Toronto, Ontario.
Vaccination of pets is important since they may contact a rabid animal when out of sight of the owner and later become rabid in the home. It is imperative that hunting dogs be vaccinated. Vaccinations should be repeated as directed by the veterinarian.
TABLE 1. Ontario mammals with rabies,
1961-1977.
Percent of All Rabies
Species Cases Positive Cases
Red Fox (Vulpes vulpes) 9274 44
Cow (Bos taurus) 4310 20
Striped Skunk (Mephitis mephitis) 3416 16
Dog (Canis familiars) 1334 6
Cat (Felis catus) 1179 6
Sheep (Ovis aries) 431 2
Horse (Equus caballus) 440 2
Pig (Sus scrofa) 276 1.5
Bat (Vespertilionidae) 163 1
Raccoon (Procyon rotor) 115 0.5
Coyote or Wolf (Canis
latrans, C. lupus) 110 0.5
Other* 76 0.5
TOTALS 21124 100
*Includes: goat (Capra hircus), woodchuck (Marmota monax), muskrat (Ondatra zibethica), bear (Ursus americanus), buffalo (Bison bison), deer (Odocoileus virginianus), fisher (Martes pennanti), donkey (Equus asinus), elk (Cervus canadensis), squirrel (Sciurus carolinensis), domestic rabbit (0ryctolagus cuniculus).