Investigation procedures for Hendra Virus
There is a range of clinical signs recognised in Hendra Virus (HeV) infected horses. When these signs occur with a suggestive history, you must immediately notify Agriculture Victoria and implement safety procedures to prevent exposure of people and horses to the suspect animal.
When a case of Hendra virus is suspected, immediately contact your nearest Agriculture Victoria District Veterinary Officer or Animal Health Officer, or alternatively call the all-hours Emergency Animal Disease Hotline 1800 675 888.
There are two case definitions for horses in Victoria where HeV infection is suspected. They are termed 'suspect cases' and 'surveillance cases'.
A suspect case definition is used to consider an animal that is suspected as being infected with HeV.
A history of either:
- known or suspected contact with Pteropid bats (including proximity to bat colonies, feeding or roosting areas and if the owner or vet has seen bats in the area)
- the investigating veterinarian considers HeV to be possible, given the clinical signs and history (including recent travel from regions where Hendra has previously occurred or are in proximity to bat colonies).
These cases are considered high risk and require urgent assessment and isolation.
Other species or nearby horses
Suspect cases includes other horses in close contact (within 5 metres) with a known Hendra virus-infected animal or direct contact with a contaminated environment – for example, death site or fomite (such as, equipment, tack, clothing, footwear) are classified as a ‘suspect’ case.
The Surveillance case definition has been developed to allow for testing of horses for HeV where there is little indication to suggest HeV, but exclusion testing would offer the investigating veterinarian and the owners of the affected animal ‘peace of mind’ as well as providing valuable surveillance data.
A horse may be considered as a Surveillance case only if all of the following conditions are met:
- does not meet the ‘suspect’ case definition
- the horse is showing clinical signs suggestive of Hendra
- Hendra virus is one of a number of differential diagnoses being considered
- the investigating veterinarian does not believe HeV is the likely cause of the clinical signs.
Assistance from Agriculture Victoria
HeV is a notifiable disease throughout Australia. Upon suspicion of the disease in Victoria it must be immediately reported to Agriculture Victoria through direct contact with your local District Veterinary Officer or the Emergency Animal Disease Hotline on 1800 675 888.
The investigation of 'suspect' cases of Hendra can be subsidised through Significant Disease Investigation (SDI) Program funding. Surveillance cases are not eligible. However, Agriculture Victoria will fund the laboratory testing of these samples to exclude Hendra virus.
Hendra exclusion testing performed in Victoria is capable of detecting both known Hendra genotypes.
Our field staff will provide direction and assistance to manage Hendra virus investigations, in collaboration with private veterinarians.
Preventing exposure of people and horses to Hendra virus
It is important that people not directly involved in the management and care of an infected (or suspected to be infected) horse are excluded from direct contact with the animal. Note that it is possible for a horse to shed virus for a short period before clinical signs become apparent.
Where contact is unavoidable, appropriate personal protective equipment (PPE) must be worn. This includes impervious boots (for example, gumboots), overalls and gloves, safety eyewear and P2 respirator mask. See Guidelines for veterinarians handling potential Hendra virus infection in horses prepared by DAFF Queensland for further details.
Where possible, areas, instruments and equipment that may have been in contact with horses affected with HeV must be properly cleaned and disinfected.
Do not conduct any necropsy (limited or full) on a suspect case until HeV has been excluded. When sampling live or dead horses, appropriate PPE must be worn by veterinarians and handlers.
Sampling for Hendra virus exclusion (suspect cases and surveillance cases)
The recommended samples to exclude HeV in both live and dead horses are:
- nasal swabs in viral transport media
- 10mL of blood collected in EDTA blood tubes
- 10mL of blood collected in plain (clot) blood tubes.
A nasal swab should only be taken from a live horse if the risk of personal exposure can be managed during sample collection.
Further information is available on Hendra virus disease.