Veterinary information for HeV
Hendra virus (HeV) is a notifiable zoonotic disease. If suspected, it must be immediately reported.
HeV has a high case fatality rate in infected people and horses and must be safely managed. Learn about:
- identifying clinical signs of the virus
- samples needed to test live and dead horses
- quarantine responsibilities for veterinarians.
Safety precautions
All suspect HeV cases should be treated as potentially infected and suitable precautions must followed. When collecting samples for testing, take steps to reduce risks of HeV transmission.
People concerned about exposure to HeV should seek medical advice and contact SA Health, or a local general practitioner.
Diagnosing HeV
There are no pathognomonic signs that define Hendra virus infection in horses, which often leads to differential diagnosis.
Horses that are infected with HeV or HeV-G2 have shown variable and often vague symptoms.
Clinical signs
Clinical signs
HeV should be considered where there is acute onset of common clinical signs. These may include:
- increased body temperature (not all cases have been febrile at examination)
- increased heart rate
- discomfort or weight shifting – both fore and hind limbs
- depression
- rapid deterioration associated with respiratory or neurological signs, leading to death.
Respiratory signs
- pulmonary oedema and congestion
- respiratory distress – increased respiratory rates
- terminal nasal discharge – can be initially clear progressing to stable white froth or stable blood stained froth
- pulmonary involvement leading to terminal weakness, ataxia and collapse.
Neurological signs
- ‘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 further observations have been recorded in individual horses infected with HeV. See the Queensland Government biosecurity guidelines for more detail.
The virus has an affinity for endothelial cells, causing systemic vasculitis. The organ or system where the greatest damage occurs would appear to contribute directly to the clinical signs seen.
In several documented HeV cases, one or more horses have died suddenly before HeV was suspected or diagnosed in another horse on the same property.
Samples for HeV
The following samples are listed in order of most to least preferred, for testing live horses:
- EDTA blood: PCR testing on EDTA samples may detect virus in cells when virus or viral genome is not present in serum.
- Swabs may detect infection earlier than blood or other clinical samples. These may be used for PCR testing:
- nasal
- oral – surface of tongue
- rectal – mucosal
- urine – taken from the ground immediately post-urination.
- Serum – plain or clotted whole blood. This allows serological testing to be undertaken, or additional diagnostic testing.
Samples from dead horses
Samples from dead horses
Collecting samples from dead horses requires limited necropsy work and these can be adequately tested for HeV.
The Australian Centre for Disease Preparedness (ACDP) at Geelong recommends the following samples:
- submandibular lymph node tissue
- blood clot obtained by cutting down onto the jugular vein.
These raise the overall test sensitivity for HeV when combined with swabs, which may help when the carcass is being held pending a full necropsy for insurance purposes.
The samples should only be taken if the associated risks can be managed, including any blood released during the procedure.
If sampling opportunity is limited in either live or dead horses, take samples from a nasal swab and whole blood in EDTA. Lithium-heparin (LiHep) blood samples are no longer preferred.
See the recommended equipment, disinfectants, and procedures for collecting samples.
Tests for HeV
Horse samples are tested for both HeV and HeV-G2. There are 3 types of testing:
- Polymerase chain reaction (PCR) test:
- detects the direct presence of virus (live or dead) in a sample
- most useful early in clinical course of disease
- conducted at ACDP
- results usually reported within 2 to 3 working days once received at laboratory.
- Enzyme linked immunosorbent assay (ELISA)
- detects the presence of HeV antibodies in a sample
- regarded as screening test – negative results are a reliable indicator that the horse does not have antibodies; however, some negative horses will return false positive results
- conducted at ACDP
- results usually reported within 2 to 3 working days once received at laboratory
- positive or indeterminate results require additional testing (VNT) to confirm whether they are a true positive and not a false positive reactor.
- Virus neutralisation test (VNT)
- indirectly detects the presence of HeV antibodies in a sample
- remains the gold standard for detecting an antibody response to HeV infection – conducted under high-level biocontainment and involves mixing blood sample with live virus
- conducted at ACDP
- results can take up to 2 weeks to complete.
Funded diagnostic testing
Funded diagnostic testing
There are no fees for laboratory diagnostic testing of suspected Hendra virus cases – this is funded by PIRSA.
It ranges from exclusion testing with a remote likelihood of disease, to exotic or emerging disease diagnosis with a high suspicion of disease.
The Biosecurity division may also pay for Gribbles Vetlab fees associated with a disease investigation, where Hendra virus is being excluded.
Authorisation of payment is required before submitting samples to the laboratory, by phoning either:
Health testing
Health testing
Health tests are used as a screening process, providing assurance that a clinically normal animal is unlikely to have a certain disease.
There is no legislative requirement for health testing horses that are moved between jurisdictions or properties. However, health testing is:
- routinely requested by some equine businesses (e.g. for NSW studs before mares can be transported to them for foaling or breeding)
- undertaken on horses before they are admitted to a veterinary hospital for procedures, such as surgery or endoscopy.
The submitter determines the type of tests conducted for health testing – usually a PCR is sufficient.
The submitting veterinarian or client is responsible for all costs associated with sending samples to the laboratory for health testing, where there is no suspicion of disease.
Quarantine responsibilities
A private veterinarian does not have the legal powers to quarantine a property but can advise the owner of voluntary actions they must implement to manage the immediate situation.
If PIRSA believes that strong action is needed to control a suspected or confirmed HeV situation, it will:
- place the premises in quarantine
- implement and assume responsibility for an animal disease control program
- notify SA Health's Communicable Disease Control Branch.
As part of this response, the Biosecurity division may retain the services of the private veterinary practitioner, who will be offered a short-term contract.
Workplace health and safety obligations will be met in collaboration with the property owner or manager and the private veterinarian.
Costs associated with the husbandry and general care of horses are treated as normal and are paid by the horse owner.
Contacts
- PIRSA, Biosecurity division, Animal Health
- Gribbles Vetlab: 8202 3300 (24 hours)
- SA Health: 1300 232 272 (24 hours, 7 days)
- Health Direct: 1800 022 222
- SafeWork SA Help Centre: 1300 365 255
Information on this page has been sourced with permission from the Queensland Government Hendra virus information for veterinarians.