Rabies – Serology

Testing Indications

Public Health Ontario Laboratory provides serology testing to determine immunity to Rabies. Individuals at risk for Rabies such as animal workers, lab workers, vets, hunters and travelers to endemic areas are given Pre-Exposure Prophylaxis as a vaccine series to protect against Rabies. Their antibody levels are monitored at regular intervals.

Diagnostic testing is not performed by Public Health Ontario Laboratory. Diagnostic laboratory tests for rabies in humans include detection of neutralizing anti-rabies virus antibodies in serum or cerebrospinal fluid (CSF) and rabies virus antigen or RNA in tissues or fluids.

The National Microbiology Laboratory (NML) provides testing for neutralizing antibody in CSF. Testing information is located here.

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

Please contact your Medical Officer of Health if you suspect Rabies infection and require laboratory diagnostic testing for Rabies virus.

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Rabies, Rabies Immunity, Rabies Pre/Post Vaccination, or Rabies post exposure immune status

Whole blood or serum

5.0 ml whole blood or 1.0 ml serum

Vacutainer tubes (SST) 

Submission and Collection Notes

1

Provide history including past vaccinations (number of shots and date), details of exposure/bite, whether RIG administered, travel, symptoms, etc. on Lab General Test Requisition Form.

Limitations

Haemolysed, icteric, lipemic or microbially contaminated sera or plasma are not recommended for testing.

Preparation Prior to Transport

Label the specimen container with the patient’s full name, date of collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Special Instructions

Centrifuge if using SST. Place specimen in biohazard bag and seal. Specimens should be stored at 2-8°C following collection and shipped to PHOL on ice packs.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Rabies serology test is performed twice per week on Tuesdays and Thursdays. 

Turnaround time is up to 7 days from receipt by PHO laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Specimens that are positive for Rabies antibodies are reported to the Medical Officer of Health as per the Health Protection and Promotion Act.

Test Methods

Rabies specimens are tested by Rapid Fluorescent Focus Inhibition Test (RFFIT) for Rabies antibody levels; usually in patients vaccinated for Rabies.

RFFIT is a neutralization test where dilutions of the patient’s serum are incubated with live rabies virus.  Tissue culture cells are then added and allowed to grow for 24 hrs. After fixation and staining, the test is read under a fluorescent microscope. 

An adequate response after vaccination is ≥ 0.5 IU/ ml as recommended by W.H.O.

Exposure to Rabies

Rabies is a preventable viral disease of mammals most often transmitted through the bite or saliva of a rabid animal such as dogs, cats, raccoons, skunks, foxes, coyotes and especially bats. Bats carry the virus asymptomatically and their bites are often difficult to detect.

Post exposure vaccination and RIG (Rabies Immune Globulin) should be administered promptly depending on the circumstances of the exposure. Once symptoms appear, rabies is almost always fatal.

Contact the local Medical Officer of Health in your area for advice on treatment and to order vaccine.



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Updated 4 Jan 2019