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Rabies

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Reporting Obligations

Confirmed and suspected cases shall be reported to the local Health Unit.

NOTE: For reporting of animal bites or other incidents where there is possibility of human exposure to rabies, refer to Animal Exposure Reporting Form below.

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Epidemiology

Aetiologic Agent

Rabies disease is caused by the rabies virus; an RNA virus classified in the Rhabdoviridae family from the genus Lyssavirus.

Clinical Presentation

During the incubation period after exposure, the person does not experience disease symptoms and the wound from the bite may heal. The prodrome begins when the virus enters the peripheral nerves and spinal cord and can last 2–10 days. Onset of clinical symptoms is generally heralded by a sense of apprehension and excitability with headache, fever, malaise and indefinite sensory changes and pain at the site of the bite. The excitation phase that follows is characterized by hypertension, increased salivation and swallowing dysfunction (hydrophobia). This may be followed by generalized paralysis. The acute neurological phase of the disease is characterized by encephalomyelitis that almost always progresses to coma or death, often due to respiratory paralysis, if no medical intervention is given.

Modes of Transmission

Rabies can be transmitted to humans through the saliva of infected animals through bites, scratches or other contact with mucosal membranes or open skin. Person to person transmission is theoretically possible but rare and not well documented. Airborne spread has been demonstrated in caves where bats roost and in laboratory settings, but this occurs very rarely. Transmission through corneal, solid organ and blood vessel transplant from unsuspected rabies cases has occurred.

Incubation Period

Usually 3–8 weeks; rarely as short as a few days or as long as several years. The incubation period depends on wound severity, wound site in relation to nerve supply and distance from the brain, the amount and strain of virus, protection provided by clothing and other factors such as adequate wound cleansing.

Period of Communicability

Rabid animals are infectious only from the time the virus reaches the salivary glands and up until death. Death in species other than rabies reservoir species usually occurs within one week of onset of clinical signs. Different species may shed virus in saliva for different lengths of time prior to onset of clinical signs. Defined periods of communicability in animal hosts are reliably known for domesticated dogs, cats and ferrets, which may shed virus in saliva for up to 10 days prior to the onset of clinical signs. Other mammals (including humans) may shed virus in saliva for up to 14 days prior to the onset of clinical signs. Wildlife rabies reservoir species may shed virus for much longer periods of time, and are not considered to have a defined period of communicability.

Risk Factors/Susceptibility

History of animal bite, particularly a wild animal, stray animal, sick animal, bat or an animal bite occurring in a rabies endemic region.

Exposure to bats in cave.

Recent corneal, solid organ or blood vessel transplant.

Diagnosis and Laboratory Testing

Confirmed Case: clinically compatible signs and symptoms with:

  • Detection of viral antigen in an appropriate clinical specimen, preferably the brain or the nerves surrounding hair follicles in the nape of the neck, by immunofluorescence OR
  • Isolation of rabies virus from saliva, cerebrospinal fluid (CSF), or central nervous system tissue using cell culture or laboratory animal OR
  • Detection of rabies virus ribonucleic acid (RNA) in an appropriate clinical specimen (e.g., saliva)

Probable Case: clinically compatible signs and symptoms with:

  • Demonstration of rabies-neutralizing antibody titre ≥ five (i.e., complete neutralization) in the serum or CSF of an unvaccinated person
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Treatment and Case Management

In cases where clinical symptoms of rabies have developed, death is invariably the outcome. Treatment is primarily supportive. Use routine practices for hospitalized cases for the duration of illness.

The Health Unit will be involved in exposure investigation and follow-up of contacts.

Patient Information

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Additional Resources

Public Health Agency of Canada. “Canadian Immunization Guide, Rabies Vaccine.”

Ministry of Health and Long-Term Care. “Management of Potential Rabies Exposures Guideline, 2019.”

References

Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2019.