Rabies is a viral infection of animals that can be transmitted to humans. It is caused by a virus of the Rhabdoviridae family, which attacks the central nervous system and eventually affects the brain. The virus is usually found in the saliva of an infected animal. Rabies is almost always fatal once symptoms occur. Rabies can occur in any warm-blooded animal, domestic and wild- commonly, dogs, cats, foxes, raccoons, skunks, wolves and bats. Animals having potential interactions with people such as cattle and horses can acquire rabies and may transmit the disease to humans.
Human rabies is rare in Canada, due largely to excellent prevention and control programs. There have been four cases of human rabies since 1985. Since 1924, a total of 24 people in six provinces have died of rabies in Canada: Quebec (12), Ontario (6), Saskatchewan and Alberta 2 each), British Columbia and Nova Scotia (1 case each). Rabies is a significant public health problem in many Asian and African countries. The World Health Organization estimates there are 55,000 human deaths from rabies each year in Asia and Africa, with 30-50% of cases occurring in children under 15 years of age.
The virus is transmitted through close contact with the saliva of infected animals, most often by a bite or scratch or by licks on broken skin or mucous membranes, such as the eyes, nose or mouth. Person-to-person transmission is theoretically possible, but rare and not well documented. Organ (corneal) transplants from persons dying of undiagnosed central nervous system (CNS) disease have resulted in rabies in recipients. Airborne spread has been demonstrated in a cave where bats were roosting and in laboratory settings, but this occurs very rarely.
Injury to the upper body or face poses the greatest risk of transmission. The risk for children is estimated to be four times greater than adults, and boys are at greater risk than girls.
Symptoms can take 20 to 60 days to appear, although this may vary from days to years, and may depend on wound severity, wound site in relation to nerve supply and distance from the brain, amount and strain of virus, protection provided by clothing, and other factors.
Symptoms progress quickly as the central nervous system is attacked, and the illness generally presents in one of two ways: “furious rabies” and “dumb rabies”. Furious rabies is more common and is characterised by anxiety and psychological disturbances (confusion, agitation, delirium, rage, hallucinations, and hydrophobia. Dumb rabies occurs in approximately 20% of patients and presents with paralysis. In both furious and dumb rabies, death usually occurs within seven days due to breathing failure caused by paralysis of the respiratory system.
Rabies is a serious disease that is almost always fatal, so post-exposure vaccination is a priority for anyone exposed to animals with proven or suspected rabies. Post-exposure vaccines in Canada are distributed through the public health system.
Rabies vaccine is also indicated for pre-exposure vaccination of people who are at high risk of contact with potentially rabid animals or the rabies virus. This includes, for example, certain laboratory workers, veterinarians, animal control and wildlife workers, spelunkers (cave explorers), hunters and trappers in high-risk areas and travellers to areas where rabies is constantly present. Pre-exposure vaccination is generally offered by private health care providers (e.g. travel clinics); some provinces offer publicly funded pre-exposure vaccine programs.
Two vaccines against rabies are currently approved for use in Canada, Imovax® Rabies, made by Sanofi Pasteur Ltd and RabAvert®, made by Novartis and distributed in Canada by Merck Frosst. The vaccines are very effective, cause few adverse reactions, and both provide immunity to rabies when administered for protection before an exposure (pre-exposure prophylaxis) or after an exposure (post-exposure prophylaxis).
About 65 per cent of the annual doses of rabies vaccine in Canada are used for post-exposure vaccination; the remaining 35% is used for pre-exposure prophylaxis. Pre-exposure prophylaxis is recommended for people of increased risk of contracting rabies, such as:
Post-exposure prophylaxis should be started as soon as possible after exposure and should be offered to exposed individuals regardless of the elapsed interval. Five doses of vaccine are needed; the first dose should be given as soon as possible after exposure and additional doses on each of days 3, 7, 14 and 28 after the first dose. Individuals exposed to rabies should also receive a dose of Rabies immunoglobulin on the same day the first dose of the vaccine is received.
If you have been bitten by an animal and think you may have been exposed to rabies, you should immediately wash and flush the wound with soap and water. Seek attention from a health care professional as soon as possible to assess your risk and treatment options.