Rabies testing at the CFIA: human specimens

On this page

• Human suspect submission process
• Human rabies cases in Canada
• Prime considerations in suspect rabies cases
• Tests offered by the CFIA Rabies Laboratory
• Summary of specimens for antemortem testing
• How to request a human sample submission for rabies
• Information on shipping options for human samples
• Contact information

Human suspect submission process

Disease investigation and factors to consider

• Encephalitis of undetermined cause, rapid deterioration, hospitalization.
• Animal bite or contact history
• Travel to a country or area where terrestrial rabies is enzootic for example, dog rabies in Africa or Asia.

Contact the CFIA Rabies laboratory in Ottawa

• After consultation with hospital regarding types of samples and urgency of testing, CFIA arranges to have staff available for specialized testing, including overtime, if required.
• CFIA provides required documentation to hospital, including the rabies sample submission form, as well as any special instructions.

Electronic form completion

• Only one form per patient, even if multiple samples are sent for testing.
• Enter information in the Rabies Sample Submission Form and email it to the laboratory. See completing the sample submission form for more information.

Packaging and shipment to lab

• Hospital collects the required samples (nuchal skin biopsy, multiple saliva samples). Package samples, include printed copy of form, and arrange for shipment to the lab.
• Package samples, include printed copy of form, and arrange for shipment to the lab. See guidelines for sample submission for more information.
• Complete and fax or email the notification page (see how to request a human sample submission for rabies) to inform the lab of shipment details.
• Track shipment until it arrives and a "Rabies Sample Receipt Notification" email is received from CFIA.

Testing and reporting of results

• When the sample is received at CFIA, an email notification will be sent to the submitter indicating the sample is "Under Test".
• CFIA conducts diagnostic testing (number and type of tests depends on the samples received) and authorizes release of test results.
• CFIA reports results by phone to submitter listed on Rabies sample submission form as tests are completed.
• Official "Report of analysis" for all samples will be emailed to all email addresses provided by submitter on the form as testing is completed.
• If rabies virus is detected, variant typing is conducted, and results are communicated to the submitter.
• Hospital notifies OLF if further testing is required (for example, testing of additional samples or monitoring of viral load in saliva).

Human rabies cases in Canada

Rabies in humans is rare in Canada. Since 1924, only 28 cases have been documented. The last reported case of domestically acquired human rabies caused by a terrestrial mammal occurred in 1967 in Richmond, ON. Since that time, all cases but two were attributed to infection from bats. The remaining two cases (1984 and 2012) were acquired in the Caribbean, the result of dog bites.

Oral vaccination programs and other disease control strategies targeting certain terrestrial wildlife species have been effective in controlling (and in some cases, eliminating) rabies in several Canadian provinces. However, not all provinces have wildlife rabies control programs, and rabies control in bat populations is not possible.

Even though bats carry their own distinct variants of the rabies virus, infected bats can transmit the virus to other mammals. These cases are referred to as "spillover". Several spillover cases from bats into domestic animals are reported each year in Canada, with the potential to transmit the virus to humans. Thus, there is still the risk of exposure to rabies from animals throughout Canada, even in the absence of known epizootics in terrestrial mammals.

In addition to a clinical picture consistent with rabies, examination of other factors is important for evaluating the possibility of rabies. Provide the laboratory with as much information as possible to assist in the selection of appropriate reagents for rabies diagnosis and virus typing.

Prime considerations in suspect rabies cases

Patient travel history

Travel to countries where rabies is endemic, particularly in dogs, should be considered a risk factor for rabies, even in the absence of a known exposure to a rabies vector. As the disease can also be caused by related Lyssaviruses, such as Australian bat Lyssavirus (ABLV), travel to countries free of rabies virus may still be a risk factor. The CFIA laboratory can provide advice on the distribution of rabies and other Lyssaviruses within Canada and worldwide.

Potential rabies exposures

The incubation period for human rabies is normally between one and three months but may vary between 10 days to more than a year. Recent or past contact with bats or other mammals is a risk factor for rabies, particularly in rabies endemic-regions. Category III exposure is defined as single or multiple transdermal bites or scratches, licks on broken skin, or contamination of mucous membranes with saliva. Category II exposure is defined as nibbling of uncovered skin or minor scratches or abrasions without bleeding. Both types of exposure can result in transmission of the virus from an infected animal to a person.

Tests offered by the CFIA Rabies Laboratory

At the CFIA Ottawa Animal Health Laboratory – Fallowfield (OLF), diagnosis of rabies in humans may be performed by the following tests:

• fluorescent antibody test (FAT) on nuchal skin biopsy (antemortem)
• brain tissue (postmortem)
• real-time reverse transcriptase polymerase chain reaction (RT-PCR) on skin, saliva or brain tissue

Virus variant typing by genetic sequence analysis or using discriminatory monoclonal antibody panels is also performed. The CFIA does not carry out serologic tests for rabies virus antibody. For serologic testing, contact the Public Health Agency of Canada (PHAC).

Nuchal skin biopsy (antemortem testing)

Skin at the nape containing many hair follicles is highly enervated. As such, rabies virus antigen may be detectable antemortem by FAT if centrifugal spread from the central nervous system (CNS) has occurred.

A full thickness biopsy of at least 5 mm and containing several hair follicles should be taken. Place moistened gauze in a container with the biopsy tissue, but do not wrap the tissue. Store at 4°C or –20°C until ready to ship.

At the lab, the skin is frozen and sectioned using a cryostat. Multiple sections are tested by the FAT. RT-PCR tests may also be performed.

If rabies virus antigen is detected, the remaining skin will be processed to extract viral RNA, and the rabies virus variant will be determined by sequence analysis. For these reasons it is important to submit a biopsy of adequate size to provide sufficient tissue for multiple tests.

Saliva (antemortem testing)

Saliva may be submitted for testing by real-time RT-PCR. Collect 2-3 ml of saliva directly into a sterile tube or aspirate and dispense into a sterile, leakproof container. Do not add preservatives or additional material. Immediately freeze at –20ºC, or lower, to prevent degradation of the viral RNA.

Serial samples taken at least 12 hours apart, and preferably 24 hours apart, will increase the sensitivity of the assay as excretion of rabies virus may be intermittent in the early stages of the disease.

The presence of bile or blood may interfere with the testing. However, if the only samples available are thus contaminated, they can still be submitted, and the laboratory will attempt to test them.

Diagnosed rabies cases and viral load monitoring

If the patient is receiving medical care in an effort to sustain life, monitoring of the rabies virus load in the saliva may be requested.

Samples should be collected at a frequency of every 24 hours. Clearly mark the date and time of collection on the individual tube.

Results will be expressed as cell culture infectious dose Equivalent Units (EU) per ml of saliva. EU is determined by interpolation of the test result on a standard curve of dilutions of known concentrations of rabies virus.

Postmortem examination of CNS tissue

Fresh (not fixed) brain tissue should be submitted for testing. A small section (1 cm x 1 cm x 1 cm) from the brain stem is suitable for diagnosis. Additional tissues such as cerebellum, pons, medulla, hippocampus and spinal cord may also be submitted. Do not submit only cerebrum as it generally has lower levels of rabies virus antigen than other parts of the brain.

Place the tissue into a leak-proof container so it will not be damaged during transit. Store the sample at 4°C or lower until ready to ship.

At the lab, the tissue will be examined by FAT. If rabies virus antigen is detected, the virus will be typed by staining with a panel of specific anti-rabies antibodies or by genetic sequencing.

Summary of specimens for antemortem testing

• No single test ante-mortem is sufficient to "rule-out" rabies.
• If onset of symptoms is <7 days, a negative test result does not exclude rabies virus infection as excretion may be intermittent and antibody response may be negligible.

Consult the following pages for more information:

• Guidelines for sample submission
• Completing the submission form

How to request a human sample submission for rabies

For human sample submissions, you must notify the laboratory by phone at (343) 212-0340. The laboratory can provide a PDF copy of the Human sample submission for rabies form, or you can download a copy from the CVMA website (consult the "Human specimens" guidance document).

Complete the form provided by the laboratory and send it to the lab by fax or email:

• fax: (343) 212-0202
• email: cfia.rabieseast-rageest.acia@inspection.gc.ca

Provide the following information:

• Submitter name
• Courier company or airline
  • It is the responsibility of the submitter to select a method of transportation that will ensure the delivery of the specimen.
• Tracking number
• Date and time of expected arrival
• Indicate if the patient was hospitalized
• Date of illness onset
• Describe the animal exposure history, if applicable
  • Include species and nature of the exposure, if applicable.
• Include travel history outside of the home province, if applicable
  • List all provinces or countries visited, if applicable
• Provide additional comments
• Indicate the samples submitted (for example, saliva, nuchal biopsy, cerebrospinal fluid or postmortem brain or CNS tissue)

A rabies sample submission form must also be completed and submitted. Enclose a copy with the shipment.

Information on shipping options for human samples

The information below applies to human samples only.

Contact information

R-Unit, Ottawa Laboratory Fallowfield
Canadian Food Inspection Agency
3851 Fallowfield Road
Ottawa ON K2J 4S1

Hours of operation: Monday to Friday, 8 am to 4 pm Eastern time
Phone: 343‑212‑0340
Fax: 343‑212‑0202
E-mail: cfia.rabieseast-rageest.acia@inspection.gc.ca