For health professionals: Rabies

Get detailed information on rabies, its clinical assessment and treatment.

On this page

• What health professionals need to know about rabies
• Clinical manifestations
• Diagnosis
• Preventing and managing rabies exposure
• Surveillance

What health professionals need to know about rabies

Rabies is a rare disease caused by a Lyssavirus of the Rhabdoviridae family. The rabies virus is highly neurotropic and causes fatal encephalomyelitis once the infection is established and reaches the brain. It is most often transmitted to humans through the bite of an infected mammal. Once infected, the virus replicates in the peripheral tissue, spreads along the peripheral nerves and spinal cord to the brain, disseminates through the central nervous system and then centrifugally spreads along nerves to various organs, including the salivary glands.

Once clinical symptoms develop, death typically occurs within 7 to 14 days, although the time of death may be influenced by critical care measures.

Rabies in humans is preventable through prompt appropriate medical care.

Globally, canine-mediated rabies continues to cause thousands of deaths every year in over 100 countries, mostly affecting communities with limited access to health and veterinary systems.

In Canada, the canine variant of rabies virus has been eliminated primarily through vaccination programs. Wildlife are the main reservoirs for rabies, and there are a number of variants that have co-evolved with their primary host species.

The variant distribution of rabies virus varies considerably geographically. Bat variants can be found across most of the country. In the Prairie Provinces, the skunk variant is predominantly found, while in Ontario, Quebec and New Brunswick, there has been a recent re-emergence of the raccoon variant from the United States, with spillover now occurring in skunks. The Arctic fox variant can be found throughout the northern regions of Canada primarily.

All variants can be transmitted both within the reservoir (host) species and also by spillover to other species. Health professionals should be aware of the epidemiology in their respective region to inform risk assessments for their patients.

Clinical manifestations

Non-specific prodromal symptoms of rabies may last for up to 10 days prior to the onset of neurologic symptoms and include:

• chills
• fever
• fatigue
• anxiety
• malaise
• anorexia
• insomnia
• irritability
• headache

About 80% of patients develop an encephalitic or classical (also called furious) form of rabies and 20% have a paralytic form of disease.

Encephalitic rabies is characterised by:

• hydrophobia (50-80% of cases), which is characteristic and not a feature of any other diseases
• aerophobia
• fever is common and may be quite high (over 42° C/107°F)
• episodes of generalized arousal or hyperexcitability, separated by lucid periods
• signs of autonomic nervous system dysfunction, including:
  • sweating
  • lacrimation
  • piloerection
  • dilated pupils
  • hypersalivation
• cranial nerve signs may be present, including:
  • facial weakness
  • ophthalmoplegia
  • tongue weakness
  • impaired swallowing
• seizures
• vocal cord weakness and voice changes
• progression to severe flaccid paralysis, coma
• multiple organ failure

Paralytic rabies is characterised by:

• prominent flaccid muscle weakness often beginning in the bitten extremity and spreading to other extremities
• inability to talk due to laryngeal muscle weakness
• urinary incontinence
• progressive weakness of bulbar and respiratory muscles, resulting in death

Diagnosis

Confirmatory diagnostic laboratory tests for rabies in humans include detection of:

• neutralizing anti-rabies virus antibodies in serum or cerebrospinal fluid (CSF)
• rabies virus antigen or RNA in tissues or fluids

The National Microbiology Laboratory (NML) provides testing for neutralizing antibody in CSF for all provinces and territories, and serology testing for all provinces and territories except Ontario. In Ontario, serology testing is conducted at the Public Health Ontario Laboratory.

Antigen/RNA detection is done at the Canadian Food Inspection Agency Ottawa Laboratory. For ante-mortem diagnosis, a Fluorescent Antibody Test (FAT) can be performed on frozen sections of nuchal skin biopsy material for detection of viral antigen. Reverse transcription polymerase chain reaction (RT-PCR) for detection of viral RNA can also be performed on skin, saliva and corneal wash samples. Post-mortem diagnosis can be performed on brain tissue using the FAT, as is also used for animal samples.

Prevention and managing rabies exposure

Immunization of high risk groups before exposure

Immunization is recommended for high risk groups, such as:

• spelunkers
• those who routinely work with animals
• laboratory workers who handle the virus
• those who travel to countries endemic for canine-mediated rabies

Workers with continuing high risk should have their blood tested (antibody titres measured) regularly to determine if booster injections are required.

Depending on the province or territory, vaccinations for certain high risk groups may be covered. For more information in your area, contact your local public health authority.

The Canadian Immunization Guide chapter on rabies vaccine is prepared by the National Advisory Committee on Immunization (NACI). It provides details on:

• vaccine recommendations in subpopulations
• scheduling and dosages
• route of administration
• serologic testing
• adverse events and reporting

Medical care after a suspect rabies exposure

First aid for rabies begins with good wound care. This can reduce the risk of rabies by up to 90%.

Follow these steps:

1. wash the wound with a soap solution
2. clean the wound to its full depth
3. flush the wound for approximately 15 minutes

Viricidal agents can be applied where appropriate. These are solutions that contain:

• iodine
• alcohol

Suturing the wound should be avoided if possible.

Following wound care, you must decide whether to institute rabies post-exposure prophylaxis (RPEP), which involves rabies immune globulin (RabIg) treatment and immunization.

Initiate RPEP based on an assessment of risk. The risk assessment and a decision to provide RPEP is often done in collaboration with local public health authorities (and possibly veterinary authorities). It depends on a number of factors, including but not limited to:

• the exposed person's age
• circumstances of the exposure (provoked or unprovoked)
• nature of the exposure (bite vs non-bite exposure)
• location and severity of the bite
• vaccination status and behaviour of the animal
• prevalence of rabies in the species of animal, by region

More detailed information on considerations during the risk assessment can be found in the Canadian Immunization Guide chapter on rabies vaccine.

Immediately following wound care, people who have had contact with the rabies virus should receive:

• Rabies immune globulin (RabIg). RabIg, which contains antibodies that neutralize the virus and provides immediate antibodies (passive immunity) that last for only a few weeks. It is given in a dose directly into the wound as soon as possible after contact. RabIg is not indicated for previously vaccinated individuals.
• Rabies vaccine (HDCV or PCECV). This vaccine should be used concurrently with RabIg to help develop active immunity. Vaccination schedules depend on previous history of vaccination and co-morbidities.

For post-exposure prophylaxis of previously unimmunized immunocompetent persons, 4 doses of vaccine should be administered on days 0, 3, 7 and 14.

Unimmunized immunocompromised persons should also receive a fifth dose on day 28, Unimmunized immunocompromised persons include those:

• who have immunosuppressive illnesses
• taking chloroquine and other antimalarials
• taking corticosteroids or other immunosuppressive agents

RabIg is not indicated and should not be given to someone who has been previously appropriately immunized. In previously appropriately immunized individuals who require post-exposure prophylaxis, only two vaccine doses are recommended on day 0 and 3 days later.

The Canadian Immunization Guide chapter on rabies vaccine should be consulted for more details on:

• wound management
• vaccine and immunoglobulin preparations approved for humans
• scheduling and dosages
• route of administration
• serologic testing
• adverse events and reporting

There is no established treatment for rabies once symptoms have begun. Almost all patients succumb to the disease or its complications within a few weeks of illness onset.

Supportive therapy includes:

• sedation
• nutrition
• intubation
• mechanical ventilation
• fluid and electrolyte management
• management of intercurrent illnesses and complications

Surveillance for human rabies in Canada

Health professionals in Canada play a critical role in identifying and reporting cases of rabies virus. Rabies is a national notifiable disease. You are to report cases to your provincial or territorial public health authorities. See the surveillance of rabies section for more information on surveillance in Canada.

Consult the national case definition for additional information.