Hendra Virus - Investigation Procedures
There is a spectrum of clinical signs recognised in HeV infected horses. When these signs occur with a suggestive history, you must immediately notify DEDJTR and implement safety procedures to prevent exposure of people and horses to the suspect case.
There are two case definitions for horses in Victoria where there is concern regarding possible HeV infection. They are "suspect cases" and "surveillance cases":
Hendra should be suspected where there is a history of either:
- Recent arrival (within last 3 weeks) from Queensland or northern NSW, or
- Known or strongly suspected contact with flying foxes (including proximity to bat colonies, feeding or roosting areas)
- The horse has suffered an acute onset of illness (or sudden death);
- The horse is showing unexplained elevated temperature and heart rate;
- where any one or more of the following clinical signs are present:
- respiratory distress;
- neurological signs (ataxia, circling, twitching, head tilt)
- depression and rapid deterioration.
The Surveillance case definition applies to horses where there is not a clear basis to suspect HeV infection, but where exclusion testing would give peace of mind to investigating veterinarians and provide valuable surveillance data.
A horse may be considered a Surveillance case where history and clinical signs do not meet the suspect case definition but the investigating veterinarian is still concerned.
If a dead horse is tested for HeV as a suspect case or surveillance case, the carcase must remain on the premises until negative results are received
Assistance from DEDJTR
HeV is a Notifiable Disease throughout Australia. Upon suspicion of the disease in Victoria it must immediately be reported to the Department of Economic Development, Jobs, Transport and Resources (DEDJTR).
DEDJTR will assist private veterinarians to make the decision about whether the case meets any or none of the case definitions. Suspect cases are eligible for Significant Disease Investigation (SDI) Program funding. Surveillance cases are not eligible, however DEDJTR will fund the laboratory testing of these samples to exclude Hendra virus.
DEDJTR field staff will provide direction and assistance to manage Hendra virus investigations, in collaboration with the private veterinarian.
For suspect cases DEDJTR will make the decision as to whether quarantine measures are needed whilst the property investigation is occurring.
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 horse are excluded from direct contact with it. Note that it is possible for a horse to shed virus for a short period before clinical signs become apparent.
Where contact with possibly infected horses is unavoidable, appropriate personal protective equipment (PPE) must be worn. This includes impervious boots, overalls and gloves, safety eyewear and P2 respirator. See a document prepared by DAFF Queensland for further details:
Guidelines for veterinarians handling potential Hendra virus infection in horses
Where possible, areas, instruments and equipment that may have been in contact with horses affected with HeV must be properly cleaned and disinfected. See the DAFF Queensland document for details.
Do not conduct any necropsy (limited or full) on a suspect case until HeV has been excluded. If sampling is undertaken for live or dead horses, it should be done with appropriate PPE and at minimal risk to the veterinarian and handlers.
Sampling for Hendra virus exclusion (suspect cases and surveillance cases)
The minimum recommended samples to exclude HeV in both live and dead horses are:
- Nasal swabs in viral transport media.
- 10 ml of blood collected in EDTA blood tubes
- 10 ml of blood collected in plain (clot) blood tubes
NB: A nasal swab should only be taken from a live horse if there is no risk of personal contamination whilst collecting.
The following samples can also be diagnostically useful and should be take if safe to do so:
- Urine swab in viral transport media (taken from ground immediately post-urination)
- Oral swab (taken from the surface of the tongue) in viral transport media
- Rectal mucosal swab (not faecal swab) in viral transport media
When a case of Hendra virus is suspected, please immediately contact your nearest DEDJTR District Veterinary Officer or Animal Health Officer, or alternatively call the all-hours Emergency Animal Disease Hotline (1800 675 888) without delay.
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