Hendra Virus Policy

Gayndah Veterinary Surgery Policy on Hendra Virus and Vaccination


Hendra virus is a fatal disease in horses and in humans. The mortality rate in horses is close to 100% and in humans is 60%. Veterinarians and their staff are at high risk of contracting Hendra virus and they account for all but two of the confirmed human cases.  Another high-risk group is owners of unvaccinated horses, especially if the horse is not diagnosed and the owner is not offered preventative treatment after exposure to the virus. Quite a number of horse owners in Qld and NSW have had emergency preventative treatment for high level exposure to Hendra Virus from their horses.

Hendra virus can cause a range of symptoms in horses.  There can be sudden fever, respiratory illness and/or neurological signs, rapid death or no symptoms whatsoever.  In some cases the onset of illness is gradual and slow over several weeks.  Hendra virus infection can present as lacerations secondary to neurological symptoms (eg. A horse gets tangled in a fence because its brain wasn’t working properly as a result of viral infection.) A variety of other symptoms may or may not be present, including laboured breathing, nasal discharge, colic, normal or low body temperatures etc.  For example, cases of apparent colic have eventually turned out to be Hendra virus infections. Cases of Hendra virus vary wildly in presenting symptoms and circumstances: any unwell horse can quite possibly be a case of Hendra virus infection, regardless of what symptoms are present or not, and whether there is known bat exposure or not. In some cases there has been no known activity of flying foxes near infected horses.

The Hendra virus has an incubation period of between 5 and 16 days in horses. The incubation period is the time from initial infection until the time when the horse shows clinical signs of illness. During this period the horse will appear to be normal and healthy, but could in fact be highly infective, which poses a significant risk to anyone handling the horse in this time. It is a proven fact that horses can produce large quantities of virus for up to 3 days before showing symptoms of illness.

It is not possible to diagnose or rule out Hendra virus infection without an exclusion test from Biosecurity Queensland. This requires sending samples to Brisbane, with results taking between 24 hours (best case scenario) and 5 days (worst case scenario over a long weekend). Much of the delay is caused by logistical problems with freight of specimens.

When it is known that a person has been exposed to Hendra virus, doctors may offer that person treatment with monoclonal antibodies. In essence, these antibodies attach to virus particles present in the person’s body and inactivate them, preventing the virus from causing the person to become ill. These antibodies appear to be highly effective if given quickly but are not effective when given after the person has become unwell from the virus.

Vaccine Safety

Many horse owners will be aware of the negative publicity on social media regarding the Hendra vaccine, and the class action brought against the manufacturer, Zoetis. It is the well-informed opinion of Gayndah Veterinary Surgery that the class action has no grounds, and we hope to see findings confirming this soon. Having investigated thoroughly, we are confident that the Hendra vaccine is safe for horses. There are numerous reasons for this, but essentially it boils down to two questions that must be answered to be confident of safety.

  1. Is there any biological or medically plausible reason the vaccine can harm horses? The answer is a resounding NO.
  2. Is there evidence that negative events happen at a higher rate in recently vaccinated horses than in the general horse population? Again, the answer is a definite and well proven NO.

Unfortunately, the non-sense about human vaccines causing autism, which was begun by a fraudulent article published in the Lancet by British doctor Andrew Wakefield (since proven to be guilty of misconduct and de-registered), is still echoing around the world, and has spilt over into the horse owning fraternity. This pseudo-science has caused fears about vaccine safety. These fears, almost without exception, are baseless.

With over 800,000 doses of Equivac HeV administered and over 180,000 horses vaccinated, reactions have been reported for 0.28% of vaccinated horses (less than 1 in 300). Compare this with humans who get a vaccination: up to 80% of people who receive a tetanus vaccination will experience a reaction at the site of the injection. The rate and types of reactions to Hendra vaccine administration are identical to the rate and types of reactions when sterile water is injected instead of a vaccine.

The Hendra vaccine has not been known to have caused a single horse death according to the APVMA adverse event records or any other validated account. While there have been rumours of horse deaths caused by vaccination on social media, they relate to horses that died of snake-bite, grain ingestion, twisted gut and other unrelated health issues, all of which happen to horses every day of the year, regardless of whether they received a vaccine in the week prior or not. When followed back to the source, these stories always, without exception, either fizzle out to nothing or are grossly distorted.

Severe vaccine reactions (such as allergic reactions) have occurred but are very rare. The vaccine is much safer than penicillin, one of the most commonly used injections in horses.

The Hendra virus vaccine has been approved for use in pregnant mares after meeting all safety and efficacy criteria set by the APVMA. The vaccine can be given to healthy horses as young as 4 months of age. Two doses between 3 and 6 weeks apart are required initially, followed by a first booster dose 6 months later, followed by annual boosters thereafter.

A horse owner will die of this virus in Australia – somewhere, sometime

Horse owners’ refusal, despite evidence of safety, to vaccinate against Hendra virus, coupled with criminal prosecution of veterinarians under WHS legislation has disheartened many horse vets in Queensland and caused many vets to refuse to attend horses that have not been vaccinated against Hendra virus. In addition, attending unwell horses that have not been vaccinated against Hendra virus incurs greatly increased expenses in time and equipment, making owners of unvaccinated horses reluctant to call vets to attend. Sadly, these two factors together have almost certainly resulted in failure to diagnose cases of Hendra virus during recent years in Queensland. To date, we have been fortunate that this has not resulted in human deaths. The worrying scenario of a horse unwell from Hendra virus not being seen by a veterinarian and not diagnosed as a Hendra virus case will eventually arise. The owner of the horse will not know they have been exposed to the virus, and by the time they are unwell it is too late to offer monoclonal antibody treatment. It is a matter of certainty that the tense situation which has arisen between horse vets, horse owners and Workplace Health and Safety Qld is going to result in the serious injury, if not death, of a horse owner sometime in the future.

Vets are responsible for the safety of other people in the vet’s workplace, including the owner or handler of a horse while the vet is working on that person’s private property. For a veterinarian to avoid prosecution for unsafe work practices they must ensure that anyone in or near their workplace complies with all safety directions the veterinarian gives while attending the horse. Anyone failing to comply with safety directions from the veterinarian must result in veterinary work ceasing immediately until the safety issues have been rectified. Failure to rectify the safety issues means that work cannot resume. In other words, to avoid prosecution the vet must do things correctly themselves, and also ensure that other people present do things correctly.

What this means for horse owners

The practical consequences of not vaccinating your horse are many, but there are several particularly important items to note:

  1. There is a known and serious risk of injury or death because of this virus.  Although infection is rare, the consequences are very serious, including deaths of horses and people. Hendra virus is categorised as a “BSL-4” virus (Bio-safety Level 4 – the same as Ebola Virus) and is considered by NAID and CDC to be a Category 3 bioterrorism agent or pathogen.
  2. Any horse that is unwell must be considered at risk of having Hendra virus (as the clinical signs are so variable) until an exclusion test has been performed. This usually takes between 24 hours and five days.  This time frame may dangerously limit treatment options for horses that are seriously unwell but do not have Hendra virus infection.
  3. Working with unvaccinated horses before exclusion results are available is only possible if WHS legislation is complied with.
  4. Working in PPE causes thermal stress even in cold conditions. We have experienced situations where wearing PPE to examine and treat unvaccinated horses IN WINTER, AT NIGHT has caused heat stress. During a warm sunny day a maximum of 5 – 10 minutes at the most before the PPE must be removed due to heat stroke means there is very little that can be done to treat unvaccinated horses. This time restriction due to heat build up in PPE is very restrictive of the type of treatment that can be provided.
  5. Workplace Health and Safety legislation and Biosecurity legislation put obligations on horse owners, horse organisations and veterinarians to control public health risks in a reasonable and practical way. Everyone has this responsibility, not just veterinarians. Legislative framework for this risk mitigation is defined by the WHS Act 2011 and Biosecurity Act 18 (2014) (effective from 1 July 2016). Both acts support a “shared approach” to managing biosecurity and WPHS obligations of people and organisations to protect the economy, the environment and the community. This means that when a veterinarian has attended an unwell horse and given advice about what to do (and what not to do) while waiting on exclusion results, any person ignoring that advice puts themselves on very shaky legal ground, even if they are on their own private property. But never mind the legal problems: no one wants to be in the position where thinking “It won’t happen to us, I’m sure my horse doesn’t have Hendra virus” turns out a day or two later to have put their kids at serious risk of injury or death – or becoming orphans.

What this means for Gayndah Vet Surgery

  1. We will require customers routinely asking us to perform veterinary work on horses to commit to vaccinating their horses. We do not undertake to provide routine care to horses that are not going to be vaccinated due to the difficulties outlined above.
  2. Sick, unvaccinated horses will be charged fees in line with the costs of personal protective equipment and the additional time required in “suiting up” and decontaminating. Owners will also be charged for the costs of an exclusion test (collecting, packaging and shipping of the sample to Brisbane).
  3. Sick, unvaccinated horses presented for emergencies will require exclusion testing and negative results prior to any invasive or risk associated treatment being provided. Treatment will be limited to that deemed necessary for the animal’s welfare and will not include invasive diagnostic procedures or therapies. In other words, treatment will be limited to collection of specimens for Hendra Virus exclusion testing and administration of drugs or euthanasia. Stomach tubing will only be performed if circumstances permit – particularly ambient temperatures and the availability of shade to work in.
  4. One of the most important treatments for colic is fluids administered by stomach tubing, repeated frequently if required. This procedure is very difficult in PPE and is not always possible if ambient temperatures are high. Delaying the administration of fluids by stomach tube for at least 24 hours will certainly have a negative impact on the outcome of colic cases. Please vaccinate your horses!
  5. All sick, unvaccinated horses will have samples collected and sent for testing for Hendra virus at the initial examination. This is not negotiable and is to ensure human health by identifying exposure.
  6. Owners of horses will be expected to comply with all safety directions when staff of Gayndah Veterinary Surgery are present, including correct use of PPE and avoiding contact with horses when not wearing appropriate PPE. Failure to comply will result in work ceasing until the safety issues are rectified. Note that contact with horses is defined as being within 5 metres of a horse.
  7. Drugs will not be prescribed, dispensed or left for administration to horses by the owners until exclusion results are negative. If drugs are required during this interval staff from Gayndah Veterinary Surgery must administer them in person. This is due to legal responsibility of Gayndah Veterinary Surgery for horse owner’s safety when administering drugs dispensed by Gayndah Veterinary Surgery.
  8. Because of the legal issues raised by prosecution of veterinarians (particularly prosecution of a veterinarian for supplying a drug for an owner to administer for treatment of a chronic medical issue 3 days before the horse became unwell and Hendra was suspected) Gayndah Veterinary Surgery will not supply any drug or medication to be administered by another person to an unvaccinated horse. This applies whether the unvaccinated horse is unwell or not.
  9. Owners of vaccinated horses not seen previously by Gayndah Veterinary Surgery should have the microchip number of the horse available to quote when making appointments. This is to enable the horse’s vaccine history to be checked before attending the horse.
  10. It will not always be possible for Gayndah Veterinary Surgery to attend an unvaccinated horse. While we make every effort to be available around the clock for emergency care, there will be times when experienced staff trained and confident in the correct use of PPE are not available within a reasonable time, or time constraints due to other work will not permit attending an unvaccinated horse. Gayndah Veterinary Surgery will not always be able to take on the complete care of an unvaccinated, unwell horse.
  11. Gayndah Veterinary Surgery cannot work with mis-representation of a horse’s vaccination status through being told incorrect microchip numbers, being told a horse is vaccinated when it isn’t, or being told a horse is vaccinated when a microchip is not present. If in doubt, say so! This avoids putting staff of Gayndah Veterinary Surgery at risk of contact with an unvaccinated horse while not wearing PPE.

Vaccination is the only way of preventing Hendra virus infection in horses and people.