Rabies

Disease Overview

Rabies is a rare disease caused by a Lyssavirus of the rhabdoviridae family, most often transmitted to humans through the bite of an infected mammal. Following infection, the virus replicates in the peripheral tissue and spreads along the peripheral nerves and spinal cord to the brain and various organs. Once the infection is established and reaches the brain, it causes encephalomyelitis. It is fatal within 7 to 14 days following the development of clinical symptoms, though the time of death may be influenced by critical care measures.^1,2

Clinical manifestations¹

Typically, the incubation period range from 1 to 3 months, but it can be as short as a few days or as long as several years after exposure.

Rabies starts with a non-specific prodromal phase. After that, the disease takes 1 of 2 forms:

• paralytic rabies (about 20% of patients)
• encephalitic or classical rabies (about 80% of patients)

Prodromal symptoms

Non-specific prodromal symptoms may last for up to 10 days prior to the onset of neurologic symptoms. 

They may include:

• pain, tingling, prickling or burning sensations at the wound site (in 80% of cases)
• flu-like symptoms such as fever, malaise, headache, fatigue and gastrointestinal issues
• occasional photophobia
• sore throat

Encephalitic rabies

Encephalitic rabies is characterized by:

• hydrophobia (33% to 50% of cases)
• aerophobia (approximately 9% of cases)
• agitation and combativeness, which may alternate with periods of calmness (50% of cases)
• symptoms of generalized arousal or hyperexcitability 

Other signs include:

• neurological signs
• signs of autonomic nervous system dysfunction
• signs of cranial nerve palsies
• progression to severe flaccid paralysis
• coma
• multiple organ failure
   

Paralytic rabies

Paralytic rabies is characterized by:

• urinary incontinence
• prominent flaccid muscle weakness often beginning in the bitten extremity and spreading to other extremities
• progressive weakness of bulbar and respiratory muscles
   

Risk factors¹

The disease is most commonly spread through bites from infected mammals. Some individuals may be more at risk, and high-risk groups include: 

• people who work with animals (dead or alive)
• hunters and trappers
• spelunkers
• laboratory workers who handle rabies virus or samples potentially containing rabies virus
• travellers to countries where rabies is transmitted more commonly

Overall Cases and Incidence^1-3

Rabies is a national notifiable disease in Canada, which means health professionals must report cases to their provincial or territorial public health authorities as soon as possible.

Around the world, canine-mediated rabies continues to cause thousands of deaths every year. In Canada, the canine variant of rabies virus has been eliminated, and wildlife is now the main reservoir for the virus. This includes bats, skunks, raccoons and foxes.

In Canada, there were 24 reported deaths between 1924 and 2009 and 1 reported case between 2013 and 2023.^2,3

Prevention and Treatment²

There is no established treatment for rabies once symptoms have begun.

The disease may be preventable through prompt appropriate medical care. This includes pre-exposure and post-exposure immunization, which may prevent the disease from entering the peripheral nervous system.

Pre-exposure immunization recommendations

Pre-exposure immunization should be offered to people included in the high-risk groups listed above. These people should undergo serological testing regularly. If they are found to have antibodies below 0.5 IU/mL, a booster dose is recommended.

• Those at continuous risk (e.g. those who work with rabies virus in a research or vaccine production laboratory) should be checked every 6 months.
• Those at frequent risk (e.g. rabies diagnostic laboratory workers, spelunkers, those who frequently handle bats, veterinarians, etc.) should be checked every 2 years.

Post-exposure immunization recommendations

Post-exposure management should take into account a risk analysis of the exposure to the potentially rabid animal and management of the exposed person. In evaluating each case, local public health officials should be consulted.

If indicated, post-exposure prophylaxis must be initiated as soon as possible, following the specific management recommendation.

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