Hendra virus

Disease in equines caused by Hendra virus (HeV) is a rare, but potentially life-threatening, zoonotic disease. Horse owners, veterinarians, their clients and staff may be required to deal with HeV at any time.

Since first becoming apparent in 1994, a much better understanding of the disease has been gathered although there are still significant gaps in knowledge. It is now clear that the virus occurs rarely and sporadically in horses. It occurs as an aberrant or spill over infection from the virus's normal wildlife host, the flying fox.

On only two occasions has there been apparent horse-to-horse spread. One horse appears to have been infected from another horse in a situation where it had immediate contact with the dead horse. In a separate outbreak, spread to several other horses occurred after a single sick mare was brought into stables from an open paddock. In this case, within the stables, the pattern of spread suggests some form of mechanical transmission.

The virus has also spread from affected horses to four humans (two of these as fatal infections). All four infected humans have had close contact with sick or dead horses. This means that this virus is unlikely to spread rapidly or easily between horses. It is much more likely that future cases will occur as sporadic, single horse cases rather than multiple-case outbreaks.

Knowledge of HeV, its cycle of infection within the flying fox population, and its occasional spill over to other species is incomplete. Ongoing research will add to this knowledge over time. These guidelines have been developed to assist with the risk management of potential cases using the best knowledge available at the time of writing, and will continue to be routinely reviewed and updated.

On this page:

• Background
• Scope
• Epidemiology
• Prevention in horses
• Response overview
• Case definition
• Recommended response strategies
• Checklist for vets
• Community concern
• Media and public communication
• Further information

1. Background

Hendra virus (HeV), previously known as equine morbillivirus (EMV), is a disease for which stringent biosecurity measures are necessary because it has the potential to be a serious zoonotic disease and there are important public health and workplace health and safety issues.

• Although the virus is not very contagious, it is important that any cases are rapidly diagnosed and that adequate precautions are taken to avoid contact between infected animals and susceptible animals and humans.
• HeV causes a broad range of clinical signs in horses. Hence many conditions could be regarded as 'possible' and require HeV exclusion. However, it is clear that HeV in the horse is a rare occurrence.
• It is known that close contact with HeV infected body fluids, particularly blood and thoracic fluid from a viraemic horse can cause infection in humans.
• As is always the case when dealing with a disease situation, it may not be clear from the outset that HeV is involved. A professional judgement is necessary to assess the risk in each 'possible' or 'probable' case and to respond in a way that is appropriate to that level of risk.
• Veterinarians who treat horses are encouraged to develop plans for responding to a potential Hendra case including the minimisation of risk to their employees and clients.

2. Scope

These guidelines are designed to support a professional risk management approach by indicating:

• the case definitions for HeV in horses
• who should be notified
• who should investigate
• what safety precautions to take
• what clinical samples should be taken and how they should be collected
• how the area should be decontaminated.

Back to top

3. Epidemiology

Epidemiological information about HeV is incomplete and is still the subject of ongoing research. Consequently this section will need to be updated as new information becomes available.

Factual information about the virus:

• It appears that flying foxes are the natural reservoir for HeV. From the limited number of events to date, transmission of HeV to aberrant hosts (horses, and in turn humans) largely overlaps the birthing season of some species of flying foxes. The actual route of infection between flying foxes and from flying foxes to horses is not yet known.
• Known sources of the virus are birthing fluids, placental material and aborted pups. Other secretions from flying foxes such as saliva, urine and faeces have not been shown to contain HeV to date. However the full cycle of infection in flying foxes is not yet known and is being researched to produce a clearer picture.
• An association with late pregnancy and the birthing season of flying foxes is consistent with the timing of five of the six HeV index cases recorded in horses - these cases having occurred between August and January, which matches the late pregnancy and birthing season of three of the four Australian flying fox species. However, the prevalence of infection in individual flying fox populations may vary from year to year, and a reliable method for prediction of the high-risk period within this time is not available.
• All HeV index horse cases have been recorded in horses that were paddocked in areas that were attractive to flying foxes. Where companion horses were present in these paddocks, only on one occasion was a companion horse infected. This animal was observed to lick the muzzle of its recumbent companion at the time of death and died 12 days later.
• Experimentally, horses have not horizontally transmitted HeV infection to other horses. Cats and guinea pigs have been shown to be experimentally susceptible to HeV infection and of these, cats demonstrated an ability to transmit infection to horses in a transmission experiment. It is not known whether cats can transmit infection to other animals or to humans.
• From information available, it can be said that the incubation period in horses (time from exposure to first signs appearing) falls between eight and 11 days. The course of illness for horses that die averages a little over two days from first signs to death. Only seven horses of the 26 horses known to have been infected survived the initial illness (a case fatality rate of over 70 %).

4. Prevention in horses

These preventive measures in horses are based on extrapolations from the limited epidemiological information available.

Stabling horses or moving them away from focal points of bat activity during the high-risk months of August to January should decrease the risk of exposure as all index cases to date have occurred in horses kept in open paddocks where bat activity has been observed. (A horse brought in from an open paddock where bats were active initiated the first observed outbreak in the stables.)

Placing horses in paddocks that do not contain trees attractive to bats for either feeding or roosting should also decrease the risk of exposure. As well, horse-feed bins or watering points should not be placed under trees when there is a risk of bats coming in to that tree for feeding, resting or roosting.

As a precaution, remove dead flying fox pups and dead flying foxes from the horse area if found. This should be done in a way that does not expose the handler to any fluids associated with the dead flying foxes. Disposal can be undertaken by burial or burning.

Back to top

5. Response overview

A response to a HeV report and resultant actions are likely to involve a range of government and non-government professionals. Good communication and the involvement of others will be essential for a successful outcome. The following table outlines the required response flow:

6. Case definition

As it is likely that horses will continue to be exposed to HeV, veterinarians will occasionally need to assess a situation for HeV risk.

HeV disease in horses is much more likely to occur as a single sick or dead horse than as a number of affected horses. Clinical signs that should prompt a veterinarian to consider HeV disease include the rapid deterioration of a horse in a paddock situation over a one to two day period with fever and signs of distress that have a respiratory system origin. After death, the discharge of large quantities of froth from the nose or mouth and other indications of severe pulmonary oedema are clear indications of the possibility of Hendra virus disease.

These guidelines aim to assist veterinarians decide whether a case is a 'possible' case (low to medium risk) or a 'probable' case (medium to high risk). The potential risk level should then guide the approach to the case. A checklist has been created, which can be used to assist in defining a potential case. Other horses may be routinely tested for HeV (that is, 'exclusion' testing completed) without them being considered to present any real risk of infection [1].

(a) Primary signs to define a 'possible' case in a horse

HeV may be involved if a peracute or acute illness [2] is seen in one or more animals in conjunction with:

• respiratory distress
• frothy nasal discharge
• elevated body temperature (above 40°C)
• elevated heart rate (increased to around 90 or 100 beats/minute).

Note: at least three of these signs must be present within 24 hours of the onset of illness to satisfy this definition of a 'possible' case.

Three or more of these signs constitute a 'possible' case and indicate a low to moderate risk of HeV.

(b) Additional signs that define a 'probable' case in a horse

Note: a 'probable' case must first satisfy the case definition of a 'possible' case (see above)[3].

In addition to those listed above, other signs that increase the likelihood of HeV being present are:

• facial oedema
• terminal bloody nasal discharge
• neurological signs - two horses that recovered had mild neurological signs, including muscle twitching. (Neurological signs may be due to either encephalitis or vascular infarcts in the brain.)

A high case fatality rate also is supportive of a 'probable' case.

One or more of these other signs (in addition to those constituting a 'possible' case) constitutes a 'probable' case and indicates a medium to high risk of HeV disease.

Note: in fatal HeV disease in horses, the principal gross pathology finding is pulmonary oedema with dilated pulmonary lymphatics.

(c) Differential diagnoses

Differential diagnoses to consider include the following:

• African horse sickness
• plant poisonings such as Crofton weed poisoning or avocado poisoning - some apparent HeV cases have turned out to be avocado poisoning and some avocado poisoning cases have turned out to be HeV
• acute septicaemias
• inhalation pneumonia or purulent bronchopneumonia
• other causes of respiratory or neurological disease.

The first step should be to exclude notifiable diseases such as HeV and African horse sickness. If confirmed as negative, sampling on subsequent sick horses should be expanded to cover more diseases.

Back to top

7. Recommended response strategies

If a case fulfills the criteria for either 'possible' or 'probable' cases, the investigation should proceed on the basis that HeV requires either confirmation or exclusion. The following information will assist with managing the response to these potential HeV cases.

(a) Immediate notification

HeV disease is notifiable and under Queensland legislation, veterinarians have a legal obligation to report all 'possible' and 'probable' HeV cases.

Report as below:

• Contact the DPI&F Business Information Centre 13 25 23
• Disease Watch Hotline (1800 675 888).

Notification of public health authorities - the Chief Veterinary Officer or delegate or the appointed case manager will advise Queensland Health in the following instances:

• when there has been significant unprotected human exposure in a 'possible' or 'probable' case (for example direct exposure to bodily fluids from a horse, with no personal protective equipment)
• when a 'probable' case is reported
• when a case is confirmed.

(b) Investigation

Practitioners should only consider proceeding with the investigation themselves after consultation with one of the people listed above. In some circumstances it may be more appropriate for the case to be investigated by DPI&F personnel.

The following points relate to an investigation of a 'possible' or 'probable' case:

• An experienced DPI&F officer should oversee the investigation, which may be conducted in conjunction with the private veterinary practitioner. This oversight may not require the officer's physical presence. In 'probable' cases it is advisable for two people (veterinarians/DPI&F Biosecurity officers) to attend, one to carry out the necropsy, the other to communicate with the owners, help with the necropsy and, if necessary, ensure security.
• The appropriate DPI&F laboratory should be informed that samples will be submitted from a 'possible' or 'probable' case of HeV disease.
• In 'probable' cases, a quarantine notice under the Stock Act 1915 may be issued immediately to ensure biosecurity of all remaining susceptible animals on the property; or alternatively some other reliable and sufficient form of disease containment applied. Quarantines can only be implemented by inspectors appointed and empowered to issue them.
• The owner should be advised that he/she is responsible for the costs which normally accrue to the owner i.e. the costs of the private practitioner, carcass burial etc. Only the costs above and beyond those that would otherwise accrue to the owner/practitioner will be covered by DPI&F (e.g. DPI&F investigation costs, AAHL samples, body bag if used).

(c) Workplace health and safety precautions

Veterinarians and practice principals need to be aware of their obligations to provide a safe working environment for their staff and persons who enter their workplace. This includes owners and persons in charge of animals on their own property that are attended by the veterinarian.

The person in charge of the workplace must ensure the workers and other persons are not exposed to risks arising out of the conduct of work of the person in charge that affect their health and safety.

• Attending veterinarians and practice principals should exclude or isolate any persons not required in the undertaking of their business.
• Attending veterinarians and practice principals should advise any owner or other contact person showing signs of ill health at or soon after a HeV disease investigation to seek medical advice AND contact their local Population Health Unit. The Department of Employment and Public Relations, Workplace Health and Safety Queensland must be informed of any incident resulting in a person suffering a work-caused illness.
• Practice principals are encouraged to develop plans for minimising the risk of contact with potentially infectious material by all staff members. This would include veterinarians who may be called to potential HeV infected animals and staff who may handle either contaminated personal protective equipment (PPE) or instruments.
• The attending veterinarian and the person in charge have an obligation to ensure any potentially infected animal does not pose a risk of infection to other animals or to people. This includes a duty to ensure that a disposal option is used that is safe and does not cause environmental harm or contamination. Disposal should be undertaken by persons who are aware of the risks and familiar with appropriate disposal methods.
• Where a veterinarian or practice principal is unsure of any procedures, they should consult with DPI&F or the Department of Employment and Industrial Relations, Workplace Health and Safety Queensland.

Back to top

Prevention of zoonotic risk

• Human infections have occurred from handling HeV-infected horses (both sick, live horses and dead horses at post-mortem examination), so great care should be taken in regard to personal safety. In particular, treat blood and other body fluids (especially respiratory and nasal secretions, saliva, and urine) and tissues as potentially infectious and take appropriate precautions to prevent contact with, or splashback of, fluids. The Medical Journal of Australia of 20 November 2006[4] contains an article titled Hendra virus infection in a veterinarian detailing a case where a veterinarian became infected with HeV after performing a necropsy on a HeV infected horse without taking adequate precautions.
• Minimise the number of people who are potentially exposed; that is, create an exclusion or isolation zone and maintain it.
• Inform people who may be potentially exposed such as owners, handlers and others (including other veterinarians) of the risk and of the appropriate procedures to be followed. Procedures to follow are outlined in the following section on protective personal equipment (PPE).
• Barrier protection in the form of gloves, respirator mask and face shield and impervious overalls and boots should be worn by all persons treating, handling or performing necropsies on 'possible' or 'probable' HeV cases. All persons involved must be appropriately trained in the use of PPE and must understand the risks present.
• Rigorous personal hygiene and hand washing is essential. Prevent contamination occurring, and if it does, wash off contamination as soon as possible. In field situations where there may not be ready access to hand washing amenities, ensure that alternative hand hygiene facilities (e.g. bucket of water and soap) are available before handling the horse. Any cuts or abrasions that become exposed or contaminated should be washed with soap and water and then be treated with either iodine-based antiseptic or ethyl alcohol.
• Those involved with necropsies should shower as soon after the procedure as possible and change into clean clothes. If non-disposable overalls are used, these should be double bagged in strong plastic bags and washed separately in hot water and bleach. Avoid contaminating vehicles and other surfaces.

Personal protective equipment (PPE)

It is recommended that the following PPE be used:

• boots
• impervious overalls (long sleeves to prevent contamination of skin where there may be cuts and abrasions) OR cotton or disposable overalls with impervious apron or impervious covering/coating
• disposable impermeable gloves (e.g. latex or nitrile) double gloved
• face shield or safety eyewear (to protect against facial splashing)
• particulate respirator. The minimum level of respiratory protection is provided by a disposable P2 particulate respirator[5]. Such respirators should be available through your normal veterinary supplier. All respirators should be fit checked prior to beginning work.

Training in selection of the correct size of P2 respirator and in donning and wearing the respirator correctly will improve safety to the wearer. For these types of respirators, the wearer must be clean-shaven to ensure an effective face-seal [6].

PPE should be donned and removed in the following sequence to minimise exposure and/or contamination. Note that this procedure is simplified. More detailed entry and exit procedural guidelines are available from the DPI&F.

• To don PPE: gown, boots, safety eyewear, gloves and respirator.
• HeV, a paramyxovirus, is susceptible to soaps, detergents and many disinfectants. It is recommended that personal decontamination take place before removing PPE. A list of effective agents is available in the AUSVETPLAN Decontamination manual available on the Animal Health Australia website.
• To remove PPE where the respirator is a P2 half face respirator or a negative pressure full face respirator: 1st pair of gloves, gown, boots, safety eyewear, respirator and second pair of gloves.
• To remove PPE where the respirator is a powered air purifying respirator (PAPR): 1st pair of gloves, PAPR, gown, boots and second pair of gloves.
• Always wash hands after removing PPE.

Field operations

• Ensure safe sharps handling and disposal to prevent accidental percutaneous exposure.
• Following accidental blood or body fluid exposure or sharps injury, wash the affected area of skin thoroughly with soap and water and/or irrigate mucous membranes with water or saline.
• Place waste (material that cannot be decontaminated e.g. gloves, absorbent materials etc.) in a sealed plastic bag and dispose of as PC 4 clinical waste in accordance with the requirements of the Environmental Protection Agency (EPA).

Necropsies

The approach to a necropsy should reflect the low level of transmissibility of this virus, the serious zoonotic potential of it, and the appropriate measures that can be taken to avoid exposure[7].

• If a field necropsy is necessary, exclude others such as handlers, owners and their families from assisting. If this is unavoidable, the person in charge of the necropsy has legal obligations under the Workplace Health and Safety Act 1995. Accordingly, the person in charge must inform others of the risk and only allow persons who are appropriately trained and provided with appropriate PPE to adopt appropriate precautions and wear the PPE listed above to assist. The person in charge must supervise all others present[8].
• Instruments used at field necropsy need to be soaked in disinfectant solution to remove gross contamination at the site of the necropsy and then sealed in strong plastic clinical waste bags and identified as potentially contaminated before transport to the clinic. Complete decontamination will require careful cleaning to avoid aerosol dissemination of residual material and autoclaving.
• Clean and disinfect the necropsy site after removal of the carcass (refer to section 7(g) - 'Decontamination'). Avoid generating splashes and aerosols, e.g. do not use a high-pressure hose.
• For further information contact Department of Employment and Industrial Relations, Workplace Health and Safety Queensland on 1300 369 915.

Back to top

(d) Samples[9]

The number of samples taken should be decided on a risk management basis guided by the case classification and the individual situation faced by the veterinarian.

Live animal

These samples are also suitable for the diagnosis of African horse sickness, a serious exotic disease that may present with similar signs.

• Nasal swabs in virus transport medium
• Blood samples
• 2 x 10 ml EDTA
• 2 x 10 ml lithium heparin
• 2 x 10 ml serum
• Urine (if possible)

Dead animal

• Blood samples - 2 x 10 ml serum
• Fresh lung, kidney and spleen and brain and/or CSF if there are neurological signs
• Fixed (formalin) lung, kidney, spleen and brain if there are neurological signs
• Exudates: nasal (if any), tracheal, bronchial [10]
• Urine

Note: if the collection of a full range of samples is judged to place the operator at unreasonable risk of exposure, then fresh and formalised lung can be submitted following a limited necropsy. Brain samples should only be collected where the facilities and PPE ensure safety.

The correct use of PPE is critical for 'probable' cases. Circumstantial evidence indicates discharges from the respiratory tract and close contact with body fluids have caused HeV infection in people in the past.

Be sure to decontaminate all sample containers and double bag them, decontaminating the inner and outer bag before removal from the property.

Contact the DPI&F to confirm final packaging and dispatch arrangements.

(e) Necropsy

General

• Where possible, the necropsy site and disposal site should be the same or very close to each other.
• Ideally necropsy and burial should occur on the property. If on-property disposal is not possible, then arrangements must be made in conjunction with the EPA to transport the animal or carcass safely to a suitable site.
• When moving a carcass, the head should be bagged to prevent discharges to the environment. The bag should be buried with the carcass.
• Where a carcass is removed from the property, the carcass is to be enclosed in a tarpaulin or body bag to prevent fluid escape. This should be buried with the carcass.
• Clean and disinfect the site of necropsy with reference to the section on Decontamination (see 7(g) below). Avoid splashes and aerosols of such a clean-up for personal safety.

'Possible' case

If the appropriate level of PPE is worn and the assessed risks associated with the particular case can be managed, a normal post-mortem can be conducted sufficient to collect the range of samples outlined plus any other samples that may assist with a diagnosis.

'Probable' case

A targeted necropsy technique may be used when the case is 'probable' and where the aim is solely to either confirm or exclude HeV.

Note: this limited approach may not allow a diagnosis of the actual cause of disease to be made if HeV tests are negative. It is not a substitute for a thorough post mortem which is the most effective way to investigate a range of differential diagnoses.

• Reflect skin from midline back over thorax.
• Remove two or three anterior ribs (with secateurs not axe) for adequate exposure, and examine the lungs and pleura in situ. Large amounts of thoracic fluid, visibly haemorrhagic lungs and dilated pulmonary lymphatics over the pleural surface would support a diagnosis of HeV.
• Collect a fresh portion of lung and also take a sample for formalin fixation. Lung pathology is used to diagnose Crofton Weed poisoning for example, the most common differential diagnosis in Queensland. Blood and blood-stained frothy fluid in the lungs would support a diagnosis of HeV.
• Similarly, remove some posterior ribs to expose the spleen and kidney.
• Collect fresh portions of spleen and kidney.
• Replace the reflected skin back over the rib cage.
• Complete a specimen advice sheet and dispatch samples to the regional DPI&F laboratory as soon as possible. Place specimen advice sheet outside the sample package so it can be read before the package is opened.
• Where the veterinarian present is experienced and trained in the use of PPE, and where that veterinarian makes a favourable risk assessment about proceeding further and where the situation permits, a more thorough post mortem could be undertaken to collect the full range of samples as for a 'possible' case.

Back to top

(f) Carcass disposal

The attending veterinarian and the person in charge have an obligation to ensure any potentially infectious animal does not pose a risk of infection to other animals or people and does not cause environmental contamination. This includes a duty to ensure disposal is undertaken in a safe manner and by persons who are aware of the risks and familiar with appropriate disposal methods.

On property

Arrangements must be made to safely dispose of the carcass. Where practicable, advice should be sought from officers of the EPA about the suitability of the disposal options for the site chosen. Deep burial has been used in the past with due regard to the choice of the burial site. If deep burial is used, DPI&F must be informed of the burial site location. DPI&F then has an obligation to report this location to the EPA if infection is confirmed.

Off property

If on-property disposal is not possible, then officers from the DPI&F and the EPA should be consulted about other options. DPI&F officers will advise about safety procedures required to move the carcass and EPA will advise on a suitable site for disposal.

The DPI&F officer should then inform the EPA of the burial site location, if deep burial is used as the disposal option.

(g) Decontamination

Decontamination is required to remove the risk of ongoing exposure to residual HeV-infected fluids.

Research conducted on the survival times for HeV has shown that the virus is resistant to a wide range of pH but susceptible to heat and desiccation [11].

Virus remained viable at 22°C for more than four days in flying fox urine and for various times (mostly under four days) in a range of fruit juices. At 37°C in both urine and juices, virus was inactivated in less than one day, demonstrating a high susceptibility to increased temperatures. HeV was tolerant of a wide pH range (2-11) but showed rapid inactivation following desiccation.

• In all cases, the area where the carcass lay and any areas where carcass fluids have contaminated the disposal site should be sprayed with a suitable disinfectant such as anhydrous sodium carbonate (soda ash) at 40g/L, or hydrated sodium carbonate (washing soda) at 100g/L, or citric acid at 2g/L.
• In 'probable' cases:
  • where possible the area should be sealed off and not accessed by susceptible species until a clear indication that HeV is not implicated.
  • if other horses are already present in the area, they may remain there provided the owner or person in charge can safely observe them for signs of disease. Horses should be clinically examined daily and their temperature taken if any abnormality is detected in gait, respiration or disposition. Temperature elevation in this context would then place that horse into the 'possible' or 'probable' category depending on other clinical signs present.

These procedures should remain in place until a diagnostic exclusion from HeV is obtained.

If HeV is confirmed these precautions should remain in place for 28 days from the commencement of clinical signs in the initial case or for 22 days from the death of the last case, whichever is the longer. These cases need to be notified to DPI&F officers.

(h) Diagnostic difficulties

• Diagnostic difficulties may mean that assessment of the risk may need to rely on clinical and pathological signs for a period of time until a laboratory diagnosis can be reached.
• Antibodies to HeV do not develop early in the acute stage of the disease and an animal may not have developed a titre until 10-14 days after infection.
• Confirming the diagnosis in a live acutely-ill animal can be particularly difficult. Virus isolation can be attempted on nasal swabs and antibody detection on serum samples, but the sensitivity of these techniques is likely to be low. Confirmation or exclusion of HeV disease will most likely only be obtained at necropsy.
• Virus isolation from the live animal might be possible from the buffy coat of the blood.
• Tests include Serum Neutralisation Test (SNT) and ELISA on serum, virus isolation on body fluids and discharges, and polymerase chain reaction (PCR) on fresh and formalised tissues.
• PCR tests are highly sensitive and can provide a good, early indication of infection.
• PCR tests are of limited diagnostic value alone and should be considered in conjunction with other results when making a diagnosis.
• Histological examination of lung (and kidney and spleen) tissue can be safely performed on formalised samples at a regional veterinary laboratory and will indicate whether lesions are consistent with HeV disease.
• Histological findings of acute severe pulmonary oedema and interstitial pneumonia are indicative of HeV disease. Fibrinoid degeneration of blood vessels throughout the body with syncytial cell formation in affected vessels is highly characteristic. Histopathology may also confirm an alternative diagnosis, for example, inhalation pneumonia or purulent bronchopneumonia or Crofton weed poisoning. Histology should therefore be undertaken as a matter of urgency.

(i) Companion animals

The attending veterinarian should also make an assessment of companion animals to the affected horse. In an experiment in the Australian Animal Health Laboratory, cats and guinea pigs developed clinical disease following infection with HeV. Dogs, rabbits, chickens, rats and mice were also exposed to HeV but did not develop clinical disease, though there was some evidence of an antibody response in some of this group.

Field evidence to date has not demonstrated HeV infection in any companion animals to the known HeV infected horses, however this potential exists and should be considered.

(j) Containment strategy

Where a case tests positive, DPI&F may quarantine the property under the Stock Act 1915 to restrict animal movement and set out any other conditions required to control the disease on that property. The quarantine would remain in force until HeV infection is controlled on that property [12].

On the property, companion horses and any other relevant animals should be sampled and tested for HeV.

Neighbouring properties should be assessed for degree of contact with the positive case. Where indicated from this assessment, any relevant animal, including horses, should then be sampled and tested. If any of these animals return positive results, the property may in turn be quarantined under the Stock Act 1915 .

No area-based movement restrictions would normally be put in place; however, this option can be implemented if considered necessary by the Chief Veterinary Officer.

Back to top

8. Checklist for vets

• Download the checklist (PDF, 30 kB).

9. Community concern

HeV disease in horses has not been proven to be a highly contagious disease, except in one situation where some mechanical means of spread in a stable was suggested from the epidemiology of that incident. Extensive serological surveillance has demonstrated that horses in the immediately surrounding areas are not at significant risk of transmission from an affected horse, but may be at increased risk due to virus transmission amongst flying foxes, possibly related to season.

10. Media and public communication

It is important that any cases of HeV disease are openly and accurately communicated to the public.

Any media enquiries should be directed to the Biosecurity spokesperson nominated at the time or to the Chief Veterinary Officer. This allows a consistent approach to be taken by people who have the best access to all information about the overall situation.

It is also recommended that all media approaches to non-departmental government officers be directed to the Biosecurity spokesperson nominated at the time or to the Chief Veterinary Officer.

If any person is approached directly by the media, they have the right to refuse to comment. If they do choose to comment, it is recommended that only facts are presented, that they are not drawn into conjecture and that they comment only on the part of the operation they were directly involved in.

11. Further information

• Checklist for vets (PDF, 30 kB)
• Hendra virus guidelines for vets (PDF, 237 kB)
• Animal Health Australia website
• Stock Act 1915 scroll down to Stock Act
• Business Information Centre

Back to top

Footnotes

1. Other horses may be sampled to exclude HeV infection for a variety of reasons, such as export certification or reassurance that someone who has been grossly contaminated with equine body fluids is not at risk of infection. Such instances are regarded as routine exclusion cases and subject to arrangements between the practitioner and the DPI&F, on a case-by-case basis. The required urgency can be determined at the time.

2. Signs of physical distress and unease are likely to be related to fever and respiratory problems. It should be noted that some of the known positive field cases had initially been diagnosed as colic.

3. The proximity of focal points for flying foxes (nearby colonies, orchards etc.) should be considered when considering the likelihood of HeV occurring. The lack of reports of flying foxes in the area would not exclude HeV.

4. Hanna, J.N., McBride, W.J., Brookes, D.L., Shield, J., Taylor, C.T., Smith, I.L., Craig, S.B., and Smith, G.A. (2006) Hendra virus infection in a veterinarian. Medical Journal of Australia, 185 (10): 562-564.

5. A standard surgical facemask is not a respirator and will not provide respiratory protection. (Refer to Australian Standard AS 1715 for information on implementing a respiratory protection program).

6. People with beards can wear a powered air-purifying respirator (PAPR) to achieve a comparable level of respiratory protection. A PAPR with appropriate filters may also provide a higher level of protection for aerosol-generating procedures such as may occur during necropsy.

7. Available evidence suggests that HeV is not readily transmissible and would not readily infect individuals who are conducting an investigation or necropsy with care, using PPE equipment and taking precautions as described above. If you become ill following contact with a suspect horse, particularly with any respiratory problem, seek medical attention promptly for investigation of possible infection, and contact the local Population Health Unit. If you become infected with HeV, it is a requirement to notify the Department of Employment and Industrial Relations, Workplace Health and Safety Queensland.

8. The person in charge of a necropsy has a duty of care for others assisting. Sections 28 to 30 of the Workplace Health and Safety Act 1995 outline obligations of persons conducting a business or undertaking and obligations of persons in control of workplaces

9. Lung samples (fresh and preserved) are the preferred samples for the diagnosis of HeV infection in horses and preferably combine these with similar samples of spleen and kidney.

10. While these samples may not be essential to confirm a diagnosis of HeV they could be useful to identify an alternative pathogen.

11. R. Fogarty, K. Halpin, B. A. Mungall, A. D. Hyatt; Effects of Environmental Conditions on Henipavirus Survival ( PDF, 2.6 mB), CSIRO, Geelong, AUSTRALIA. at ICEID 2006 March 19-22 Atlanta , Georgia, USA.

12. These periods are based on twice the known incubation period/horse survival time. The known incubation period of field horse cases ranges from eight to 11 days. The longest survival time for a horse that died from the infection is 14 days. The use of twice the incubation period conforms to accepted international standards for a range of diseases.

Information gathered from CSIRO

MEDICAL PAGE | BULLETIN BOARD