Reservoir
Rabies is a disease of mammals, both domestic and wild. Dogs are the main carriers of the disease in Asia and Africa. In Canada and the US, foxes, skunks, raccoons and bats may be reservoirs capable of transmitting infection to dogs, cats, livestock and people.
Transmission
Rabies is spread to humans when virus in the saliva of an infected animal enters through a bite, scratch, broken skin, the mucous membranes or the respiratory tract. The virus then gains access to the central nervous system through peripheral nerves. Bites from an infected animal are the main route of exposure. Transmission also occurs through transplantation of organs from undiagnosed infected persons. The usual incubation period is proportional to the distance from the portal of entry to the brain, and may vary from several days to years (most commonly 3 to 8 weeks).
Risk factors
People who work in close contact with animals, such as veterinarians and veterinary staff, animal control and wildlife workers, and laboratory workers who handle the rabies virus are at higher risk for exposure to rabies. Individuals who engage in activities such as hunting and trapping or cave exploration (spelunkers) that place them in close contact with potentially rabid animals, such as bats, foxes, skunks and raccoons, in areas where rabies is found, may also be considered at higher risk of rabies exposure.
Children are considered at higher risk for exposure to rabies because they may be more likely to approach animals and are less likely to report bites or scratches. Additionally, children may be more likely to be bitten on the face which carries a higher risk of infection and bites to children can be severe.
Risk to travellers varies depending on itinerary, purpose and duration of the trip, as well as activities and access to medical care.
Spectrum of clinical illness
Rabies is an almost always fatal viral infection of the central nervous system. Early symptoms of rabies may include headache, malaise, fever and fatigue. There may be discomfort or pain at the exposure site (i.e., the site where the person was bitten). Symptoms progress quickly as the central nervous system is attacked, and the illness generally presents in one of two ways. The more common, agitated (furious) form presents with the classic symptoms of hydrophobia and aerophobia (severe laryngeal or diaphragmatic spasms and a sensation of choking when attempting to drink or when air is blown in the face) with a rapidly progressing encephalitis and death. The paralytic form of the disease manifests in progressive flaccid paralysis, has a more protracted course, and is more difficult to diagnose. A more detailed description of the clinical signs of rabies in animals is available at: Fact Sheet: Rabies.
Disease distribution
Incidence/prevalence of human rabies
Global
Rabies occurs worldwide, although most human deaths occur in Asia and Africa. In recent years, bat-related rabies has become the most important public health concern for rabies in the Americas and the Caribbean. A map of the areas where rabies transmission occurs is available from the World Health Organization (WHO) website: Rabies countries or areas at risk.
National
Human rabies occurs very rarely in Canada. Between 1924 and 2009, 24 people in six provinces died of rabies (Figure 1): Quebec (12), Ontario (6), Saskatchewan (2), Alberta (2), British Columbia (1) and Nova Scotia (1). The three most recent human cases in Canada were bat-related; the cases occurred in Quebec in 2000, British Columbia in 2003 and Alberta in 2007.
Rabies incidence rates are similar in Canada and the US and are reported in cases per billion person-years because of the extremely low number of cases. Between 1990 and September 2007, 36 bat-related human rabies cases were identified in Canada (3 cases) and the US (33 cases), resulting in an incidence rate of 6.7 cases per billion person-years. Of these 36 bat-related human cases, the types of exposures reported were as follows:
- Direct contact with a bat: 52.8%
- With recognized bite: 27.8%
- Without recognized bite: 25%
- History of household exposure to a bat: 16.7%
- No history of exposure to a bat: 30.5%
Figure 1: Rabies - Number of Deaths in Canada, 1924-2009
Figure 1: Rabies - Number of Deaths in Canada, 1924-2009 - Text Equivalent
Incidence/prevalence of animal rabies
Rabies testing of animals is carried out mainly when there has been a possible exposure involving a human or other animal, or for special studies. Therefore, the incidence and prevalence data for animal rabies are influenced by the likelihood that an animal will have these types of encounters in the different jurisdictions, and that the animal will be captured and submitted for testing. The number of rabid animals detected in Canada has decreased considerably from 670 in 2000 to 145 in 2009. Part of this decline is related to wildlife rabies control measures, such as oral rabies vaccinations delivered through baiting programs and trap-vaccinate-release programs.
There are regional differences in the prevalence of animal rabies and the specific species infected in each region vary over time. Therefore, it is important for health care providers to consult local public health departments regarding local epidemiology and for public health officials to remain current, based on information from the Canadian Food Inspection Agency (CFIA) website: Positive Rabies in Canada
Between 2006 and 2010, a total of 1005 cases of confirmed animal rabies were reported in Canada. Four provinces accounted for the majority of these cases: Ontario (35%), Manitoba (22%), Quebec (16%) and Saskatchewan (13%). North West Territories had 66 cases (6.5%), British Columbia 54 cases (5%), and Alberta 11 (11%). Nova Scotia reported 3 cases, New Brunswick 2 cases and Prince Edward Island 1 case. The Yukon, and Newfoundland and Labrador, had no reported cases of animal rabies.
Over the same time period, skunks accounted for 37% of reported cases, followed by bats (33%), raccoons (9%) and foxes (6%). Dogs accounted for 4% and cats accounted for 2% of animal rabies cases. The species most commonly identified as having rabies by region, based on total numbers of positive test results, were as follows: foxes in the Northwest Territories and Nunavut Territory (70%), skunks in Manitoba (75%) and Saskatchewan (70%), and bats in British Columbia (99%), Alberta (81%), Quebec (70% since 2008 when raccoon rabies was last detected) and Ontario (56%); In Ontario, the second most affected species was skunks (27%).
Raccoon rabies arrived in Canada from the US in 1999 and was found mainly in Ontario, New Brunswick, and Quebec. A small number of rabid raccoons were also found in Manitoba and Saskatchewan. An active eradication program was put in place and, based on reports to September 2011, no rabid raccoons have been detected in Canada since 2008.
Rabies occurs in larger rodents such as ground hogs (woodchucks) and beavers in some areas of the US. Rabies in these animals is rare in Canada with only three rabid ground hogs (woodchucks) detected from 1998 to mid-2011, two in Manitoba in 1999 and one in Ontario in 2000.
Rabid bats have been found in most regions across Canada. The prevalence of rabies in wild bats is generally unknown, although older studies suggest a prevalence of between less than 1% and 4.1%. In 2006, the CFIA tested 2,150 bats, 3.3% of which were positive.
Bat strains of rabies virus have occasionally been identified in other animals such as foxes, cows, horses, squirrels, skunks, dogs and cats. Almost any mammal that has been exposed to an infected bat may become infected. No human cases of rabies associated with bat strains have been known to be transmitted from exposure to other animals.
Preparations available for use in Canada
Rabies vaccines (Rab)
- IMOVAX® Rabies (inactivated, human diploid cell rabies vaccine). Sanofi Pasteur Ltd. (HDCV)
- RabAvert® (inactivated, purified chick embryo cell rabies vaccine), Novartis Vaccines and Diagnostics (manufacturer), Novartis Pharmaceuticals Canada Inc. (distributor). (PCECV)
Rabies immunoglobulins (RabIg)
- IMOGAM® Rabies Pasteurized (rabies immunoglobulin [human]), Sanofi Pasteur Ltd.
- HYPERRAB® (150 IU/mL, rabies immunoglobulin [human]), Grifols Therapeutics LLC.
- HyperRAB® (300 IU/mL, rabies immunoglobulin [human]), Grifols Therapeutics LLC.*
- KamRABTM (rabies immunoglobulin [human]), Kamada Ltd.*
