Tick-borne encephalitis (TBE) Serology and PCR– Referred Out

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Background

This page provides information on the testing available for Tick-borne encephalitis (TBE), caused by the Tick-borne encephalitis virus (TBEV). Testing for TBE and the TBEV is not performed at PHO’s laboratory and requests for serology and polymerase chain reaction (PCR) tests are referred to the National Microbiology Laboratory (NML) in Winnipeg.

The TBEV is a single-stranded RNA virus that is a member of the Flaviviridae family and is known to affect the central nervous system. The primary route of transmission for this virus is through a tick bite, but can also occur by other means (e.g. ingestion of contaminated unpasteurized milk products). There are three main subtypes of TBEV that occur in Europe and parts of Asia: European, Far Eastern (Russian Spring-Summer), and Siberian subtypes. Testing for TBEV infection involves serology and/or PCR depending on the specific clinical scenario.

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Testing Indications

Most TBE virus (TBEV) infections are asymptomatic and testing is not indicated in these cases. TBE can manifest as a two-phased illness in those individuals that develop symptoms. The first phase is associated with symptoms that include fever, fatigue, headache, muscular ache, and nausea. The second phase involves the neurological system with symptoms of meningitis and/or encephalitis.² The Far Eastern (Russian Spring-Summer) variety of TBE causes a monophasic illness, and can cause more severe disease than the other two subtypes. Testing is indicated for individuals with compatible clinical symptoms and exposure history.

The diagnosis of TBE is based on the detection of specific IgM antibodies in cerebrospinal fluid (intrathecal production) and/or serum. TBE antibodies appear within 6 days after symptom onset and can be detected when neurological symptoms are present. Specific IgM antibodies can persist for up to 10 months in individuals who acquired the infection naturally. Cross-reactivity of IgG antibody with that of other flaviviruses may be possible. Detection by PCR methods may be valuable for an early differential diagnosis of TBE.¹

TBEV test requests are referred out to the National Microbiology Laboratory (NML) for testing. All specimen types for TBE require shipping under the Emergency Response Assistance Plan (ERAP)³ regardless of patient’s clinical status and reason for testing. Submitters should ensure that a Transportation of Dangerous Goods (TDG) certified individual is available to ship the specimens. PHO’s laboratory will assist in facilitation of the ERAP process during the shipment.

Testing for TBEV requires prior approval by PHO’s laboratory. Contact PHO’s Laboratory Customer Service Centre at 416-235-6556/1-877-604-4567 or the After-Hours Emergency Duty Officer at 416-605-3113 prior to sample collection and submission.

Acceptance/Rejection Criteria

Specimens received without the appropriate forms (See: Submission and Collection Notes) will not be tested.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
TBEV serology (IgG and IgM)	General Test Requisition Arbovirus (Non-Zika) Testing Intake Form	Serum³	0.5 mL	Red top or serum separator tubes
TBEV molecular detection	General Test Requisition Arbovirus (Non-Zika) Testing Intake Form	Whole blood, serum³, plasma, CSF, or tissues	0.5 mL	Red top or serum separator tubes, EDTA, citrated or heparinized tube, or Sterile tube/container

Submission and Collection Notes

Effective October 3, 2022, the Arbovirus (Non-Zika) Testing Intake Form is a mandatory requirement for Tick-borne encephalitis virus testing. PHO’s laboratory utilizes the information on the requisition and the mandatory intake form to assess testing criteria, assign appropriate tests, and provide mandatory information required by NML for relevant testing performed there.

Clinical information must be provided on the requisition before testing will be performed. Specimens not meeting criteria will be rejected for testing. Under special circumstances, testing will be considered on a case-by-case basis.

Centrifugation of serum tubes (e.g. SST) is not required and should be avoided.

Molecular testing is not a routine test. NML will determine if molecular testing is appropriate after serological testing is complete.

Label the specimen 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.

Limitations

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

Storage and Transport

Requests for TBEV testing require prior approval by PHO’s laboratory. Contact PHO’s laboratory at 416-235-6556 or 1-877-604-4567 before collecting and sending the specimens.

Follow institutional and provincial guidelines as well as Transport Canada’s Transportation of Dangerous Goods Regulations (TDGR), including their Shipping Infectious Substance Bulletin for specimen collection, transportation and storage. Store specimens in refrigerator or frozen until they are being shipped for testing. Serum can be shipped refrigerated or frozen. Avoid freezing whole blood samples. Tissues should be shipped frozen. Ship frozen specimens on dry ice and refrigerated specimens on ice packs.

Special Instructions

Specimens should be shipped out as Category A, UN 2814, and require initiation of ERAP. Contact PHO’s Laboratory Customer Service Centre to request assistance in shipping these types of samples.

Each specimen submitted for testing must be accompanied by a separate PHO General Test Requisition. All fields on each requisition must be completed.

It is MANDATORY to submit the Arbovirus (Non-Zika) Information Intake Form, where specified, with all fields completed. If all of the requested information from the Arbovirus (Non-Zika) Intake Form has been provided on the PHO General Test Requisition, we do not require an additional Arbovirus (Non-Zika) Testing Intake Form. Specimens submitted with this mandatory information missing will not be tested until that information is provided.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Turnaround time for all TBE testing is 14 calendar days from receipt of specimens at NML.

Test Methods

TBEV serology (IgG and IgM) is performed at the National Microbiology Laboratory using an Enzyme Linked Immunosorbent Assay (ELISA) assay.

Molecular detection of TBEV is performed at the National Microbiology Laboratory by PCR.

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

Positive specimens are reported to the Medical Officer of Health as per the Ontario Health Protection and Promotion Act.

References

European Centre for Disease Prevention and Control. Factsheet about tick-borne encephalitis (TBE) [Internet]. Sweden: European Centre for Disease Prevention and Control; [cited 2023 September]. Available from: https://www.ecdc.europa.eu/en/tick-borne-encephalitis/facts/factsheet#:~:text=Tickborne%20encephalitis%20is%20caused%20by,subtype%2C%20transmitted%20mainly%20by%20I.