Submitting samples for Japanese encephalitis testing
Where to submit samples
Submit samples from clinically consistent cases directly to the Biosecurity Sciences Laboratory (BSL), using these advice sheets:
Laboratory testing of pigs and horses with signs consistent with clinical Japanese encephalitis (JE), where appropriate samples have been submitted, will be fully subsidised by the Queensland Government.
Samples required
Complete and suitable samples support a thorough diagnostic work-up and improves the likelihood of reliable and meaningful results.
Post-mortem
Post-mortem specimens should be collected from animals with neurological signs killed in the acute stage of the disease or from recently dead animals.
Pigs less than 6 months or aborted foetuses
- Fresh specimens (collected into separate, clearly labelled containers)
- placenta (from aborted foetuses)*
- brain (aseptically removed if possible)*
- spinal cord*
- cerebrospinal fluid (CSF)
- tonsil*
- lung*
- heart*
- spleen*
- liver*
- kidney*
- abdominal and/or thoracic fluid
- Formalin-fixed specimens (*as listed above) in 1 container per animal necropsied
- Whole fresh aborted or stillborn foetuses are also suitable for submission where samples can't be collected on the farm
Horses with neurological signs
- Appropriate specimens for Hendra virus exclusion—Hendra virus should be excluded before progressing to invasive sampling or post mortem
- CSF (in sterile container)
- Fresh and formalin-fixed tissues (including brain and spinal cord)
Ante-mortem
- From animals in the acute stage of disease, collect whole blood (EDTA) and serum samples for virus detection and serology. For serum, collect at least 7–10mL of blood from animals in the acute phase and convalescent stage of disease (2–4 weeks apart).
- CSF should be collected from animals presenting with neurological signs. Hendra virus should be excluded first for horses.
Ideally, separate serum from clot before shipment and submit both.
Fresh semen from boars with sperm abnormalities may be considered as an additional sample for virus detection in pigs.
Transporting samples
- Chill blood samples and unpreserved tissue samples at 4°C. Note: Do not freeze samples
- Send samples in esky with frozen gel packs
- Formalin-fixed tissue can be sent at room temperature
- If mummified, stillborn or abnormal piglets are submitted they should be sent:
- double bagged—using strong plastic to avoid leakage of sample
- chilled—on ice or with ample frozen gel packs
- Ensure the necessary paperwork is submitted in hardcopy with the specimens (place in a separate zip-lock bag).
Contact BSL if you have any queries about submitting your samples.
Laboratory testing
A confirmed diagnosis of JEV infection can be made through these methods:
- isolation and identification of JEV
- detection of JEV by nucleic acid testing
- seroconversion or a significant increase in JEV-specific* antibody level by testing paired serum samples in a virus neutralisation test
- detection of elevated levels of JEV–specific* IgM antibody in CSF.
Evidence of exposure to JEV can be based on:
- detection of elevated levels of JEV-specific* IgG antibody in CSF
- detection of elevated levels of JEV–specific* antibody (IgM or IgG) in serum.
* There is a high degree of serological cross-reactivity between flaviviruses, particularly in the case of closely related viruses Murray Valley encephalitis virus and West Nile virus – Kunjin subtype.
Testing should be carried out at laboratories experienced in flavivirus serology testing, and it is important to consult laboratory staff for guidance on interpreting results.
Molecular tests (reverse transcriptase-PCR) are the preferred method for laboratory diagnosis, and can be performed on a range of unpreserved tissue samples collected post-mortem. Ante-mortem samples, such as CSF can also be tested by PCR, however this has a low sensitivity due to a short (up to 3 days in horses) viraemic phase.