Virus neutralisation test (VNT) Indirectly detects the presence of HeV antibodies in a sample.
The test involves mixing blood sample with live virus to see if virus is killed (neutralised) by antibodies and must be conducted under highlevel biocontainment.
As such, all VNT are conducted at AAHL in Geelong.
Any positive (or indeterminate) ELISA will go on for VNT.
Can take up to two weeks to complete.
Remains the gold standard for detection of an antibody response to HeV infection. Some other clinical observations that have been noted include the following.
Respiratory signs, including: pulmonary oedema and congestion respiratory distress—increased respiratory rates terminal nasal discharge—can be initially clear progressing to stable white froth and/or stable blood stained froth pulmonary involvement leading to terminal weakness, ataxia and collapse.
Neurological signs, including: ‘wobbly gait’ progressing to ataxia altered consciousness—apparent loss of vision in one or both eyes, aimless walking in a dazed state head tilting, circling muscle twitching—myoclonic spasms have been seen in acutely ill and recovered horses urinary incontinence recumbency with inability to rise.
A range of other observations have also been recorded in individual horses infected with HeV.
The guidelines have more detail if required. Diagnostic testing fees Fees are not charged for laboratory diagnostic testing of suspected cases of Hendra virus.
This may range from exclusion testing with a remote likelihood of disease to exotic/emerging disease diagnosis with a high suspicion of disease.
Biosecurity SA may also pay for other VETLAB fees associated with a disease investigation where Hendra virus is being excluded.
However, authorisation of payment is required before submitting samples to the laboratory, by phoning a Biosecurity SA Veterinary Officer or the Emergency Animal Disease Watch Hotline on 1800 675 888 (24 hours). Differential diagnoses Acute death: plant poisonings (Crofton weed, avocado) chemical poisonings—paraquat, lead, fluoroacetate, ionophores (such as monensin) colic intoxications (botulism) acute bacterial diseases (anthrax).
Respiratory or neurological disease: inhalation pneumonia or purulent bronchopneumonia equine herpes virus (neurological strain) Murray Valley encephalitis exotic disease viruses—African horse sickness, equine influenza, Japanese encephalitis, West Nile virus, encephalitides (eastern, western, Venezuelan), hantavirus pulmonary syndrome Understanding Hendra virus Health testing Health tests are used as a screening process to provide additional assurance that a clinically normal animal is unlikely to have a certain disease.
Some equine businesses have started to routinely request HeV health testing, including some New South Wales studs that require HeV health testing before mares can be transported to them for foaling or breeding.
Health testing has also been undertaken on horses before they are admitted to a veterinary hospital for certain procedures (ie surgery, endoscopy).
The submitter determines the type of tests conducted for health testing.
Usually a PCR is sufficient. 6 Understanding Hendra virus 3 acute septicaemia purpura haemorrhagica snake bite envenomation. Dead horses can be sampled adequately for HeV testing without conducting a complete necropsy.
Australian Animal Health Laboratory (AAHL) have recommended the following tissue samples from dead horses may be useful but only where collection risks can be managed, including any release of free blood during the procedure, and where it is safe to do so.
Collection of these samples will raise the overall test sensitivity for HeV when combined with swabs.
This may be of particular value where the carcass is being held pending a full necropsy for insurance purposes.
Submandibular lymph node blood clot obtained by cutting down onto the jugular vein.
Consider taking duplicate samples to allow further diagnostic work if the samples are HeV negative. Sampling Collecting samples to test for HeV should only be performed if the risk to personal safety is adequately managed and suitable personal protective equipment (PPE) is worn.
Note: If sampling opportunity is limited, the most valuable samples in either a live or dead horse are a nasal swab and whole blood in EDTA and/or lithium heparin.
Taking samples from multiple sites from each horse will increase the diagnostic sensitivity of the sampling procedure as a whole.
Types of samples recommended for HeV in live or dead horses: blood sample (1 x 10 ml of whole blood in a plain tube, 1 x 10 ml of blood in EDTA and 1 x 10 ml of blood in lithium heparin).
We recommend using anti-drip vacutainer needles for blood collection nasal swab oral swab (taken from the surface of the tongue) rectal mucosal swab (not faecal swab) urine swab (taken from the ground immediately post-urination).
It is preferable to transport swabs in virus transport medium (VTM) if available.
A small amount of saline can be used if VTM is not available.
Samples should be submitted to the laboratory in the shortest time possible.
It is important to notify VETLAB to advise them of the submission.
Where there is high suspicion of disease or significant human exposure, quicker turn around times for laboratory results can be achieved by using special courier services and weekend laboratory testing.
It is important to advise Biosecurity SA and VETLAB of the higher urgency of the laboratory results.
Keep samples refrigerated, NOT frozen.
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