Hendra virus

Previously known as Equine morbillivirus infection


Description

Hendra virus is an RNA virus that is a member of the Paramyxoviridae family of viruses and is classified in the genus Henipavirus. Flying foxes (Pteropus spp. - fruit bats) are the natural reservoir of Hendra virus.

Horses, dogs and humans have been naturally infected with Hendra virus, with high case fatality rates in horses and humans.

Transmission of Hendra virus from horse to horse appears to be relatively inefficient, but has occurred among horses in close contact, including some horses in paddock situations. Transmission is more effective among stabled horses. There is no evidence of direct transmission of Hendra virus infection from flying foxes to humans. Transmission by fomites (e.g. contaminated tack) cannot be excluded, however the virus is thought to survive for only a short time in the environment and is readily inactivated by detergents and disinfectants.

Current Situation

  • All known Hendra virus cases have occurred in Queensland or northern NSW, but cases could occur wherever there are flying foxes or in horses that had recent contact with flying foxes prior to movement.
  • Hendra virus infection was first recognised in 1994 in Australia, when it caused an outbreak of acute, fatal respiratory disease that killed 14 horses. The virus was initially called equine morbillivirus.
  • During the first outbreak, the horse-trainer also died and there was a non-fatal infection of another person closely involved with the sick horses. A retrospective diagnosis was made of a prior case (also in 1994) involving the death of two horses and a human.
  • From 1994 to 2010, Hendra virus was confirmed on an additional 11 premises in Queensland and one premise in northern New South Wales.
  • Subsequently, there has been a rise in the number of cases with 18 further incidents in Queensland and northern New South Wales between June to October 2011 alone. Twenty-one incidents (15 in Queensland and 6 in northern NSW) occurred between 2012 to the end of 2015.
  • Hendra infection has also been detected in two dogs that were in close contact with infected horses. Both dogs remained clinically normal with no history of related illness.
  • Seven cases of human infection have been detected. Four of these cases have been fatal. One of the human deaths occurred 14 months after initial exposure during the post-mortem examination of an affected horse.
  • Updated statistics on Hendra virus outbreaks, including locations, dates and confirmed human and animal cases may be found on the Australian Veterinary Association website.

Clinical signs

Clinical signs are highly variable but usually have a very rapid, acute onset and range from mild to severe. The incubation period for Hendra virus in horses ranges from 5 to 16 days. Signs consistent with colic have been the initial sign described in many cases. Dead horses may appear to have met with misadventure. Many horses are found dead with few, if any, prior signs.

Clinical signs of Hendra virus include:

  • A high case fatality rate
  • Pyrexia (fever)
  • Discomfort (weight shifting between legs)
  • Neurological changes
    • Aataxia - “wobbly gait”
    • Head-pressing
    • Muscle twitching
    • Depression
    • Altered consciousness - “dazed”
    • Aimless walking
    • Aead tilting
    • Circling
    • Apparent blindness
    • Urinary incontinence
  • Respiratory distress
    • Dyspnoea
    • Tachypnoea
    • White or blood-tinged frothy discharge from the mouth and nares, particularly in the terminal stages
  • Weakness
  • Collapse with inability to rise and/or sudden death.

Control

  • Infection control practices to minimise Hendra virus risks include wearing suitable personal protective equipment (PPE) to protect against contact with the horse and its blood and body substances, and adopting personal hygiene and decontamination practices. All persons who are at risk, including assisting persons, should be properly protected.
  • No vaccine is currently available for use in humans.
  • A vaccine against Hendra virus has been developed for horses and is commercially available. Find out more information on the vaccine.

Investigation of suspected Hendra cases

  • Veterinarians should take rigorous biosecurity and safety precautions. This includes doing a risk assessment and deciding on suitable control measures. Also see Hendra virus Work Health and Safety responsibilities (PDF, 43.89 KB).
  • Veterinarians should consider entry and exit procedures, the use of personal protective equipment (PPE) and disinfectants, disposal of potentially contaminated materials and packing and dispatch of laboratory samples.
  • Suitable PPE includes:
    • Splash-proof overalls (long sleeves to prevent contamination of skin where there may be cuts and abrasions).
    • Cotton or disposable overalls with impervious or splash-proof apron.
    • Impervious boots.
    • Double gloves.
    • Face shield or safety glasses.
    • P2 particulate respirator mask to prevent inhalation of aerosols.

    Note: People who have beards require specialised respiratory protection with full face shields and filtered air supplied by electric fans powered by portable power units.

  • Hendra virus is readily detected in swabs from external orifices and blood. Infected horses may have a high virus load throughout most organs and body fluids, and veterinarians collecting tissues from highly suspect horses must be fully confident with their PPE, infection control and sampling practices.

Diagnosis and tests available

Diagnosis

The clinical signs of Hendra virus disease are not pathognomonic, and because this is an important zoonotic disease, it is important that samples are collected for laboratory confirmation or exclusion of Hendra virus infection.

Tests available

Test

Sample(s) required

Days of the week test is conducted

Turnaround time1

Hendra virus ELISA

Clotted blood (red top tube)

Batch tested weekly

7 days

Hendra virus real time PCR

Swab(s) in PBGS, clotted blood (red top tube) or EDTA blood (purple top tube)

According to demand2

Same day to 48 hours3

1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.
2 Prior approval of delivery and testing on Saturday is required. Please contact Customer Service on 1800 675 623 to seek approval.
3 Turnaround time is dependent on urgency.

Specimen requirements

Please submit a wide range of samples to:

  • Increase the overall diagnostic sensitivity
  • Provide more information about the potential for virus excretion and transmission from a positive animal.
  • Increase the confidence in a negative Hendra virus diagnosis

Live horses

(From each horse in order of priority)

Blood (without anti-coagulant)

  • 10 ml of blood collected into a plain evacuated tube
    • Submit chilled
    • Do not use serum separator tubes

Blood (with anti-coagulant)

  • 10 ml of blood collected into an EDTA treated evacuated tube
    • Submit chilled
  • 10 ml of blood collected into lithium heparin treated evacuated tube
    • Submit chilled

Swab

  • Nasal swabs - Mucosal surface of each nostril, collected separately into viral transport media (PBGS)
    • Submitted chilled
    • DO NOT use commercially prepared swabs with plastic sleeves that contain transport medium. Tubes containing PBGS can be supplied by the laboratory. If PBGS is not available, swabs should be placed in 2 ml sterile saline.
  • Swabs from other mucosal surfaces - Oral cavity, rectum (rectal mucosa not faeces), conjunctiva, and vagina.
    • Collect separately into PBGS and submit chilled.
    • DO NOT use commercially prepared swabs with plastic sleeves that contain transport medium. Tubes containing PBGS are available from EMAI. If PBGS is not available, swabs should be placed in 2 ml sterile saline.

Dead Horses

Blood (without anti-coagulant)

  • 10 ml of blood collected into a plain evacuated tube. The jugular vein usually provides the simplest means for collecting this blood however if blood cannot be collected into an evacuated tube because of clotting, collect the blood into 2 x 5 ml screw-topped tubes. Wipe blood off the thread on the tubes before replacing the lid.
    • Submit chilled

Swabs

  • As per live horse

Cats & dogs

  • Collect samples as for horses except that 5 ml blood tubes may be used. Tubes should be filled.
  • Oral swabs should be collected from the posterior pharynx and tonsillar region
    • Sedation may be required to collect adequate diagnostic samples

Further information

Note

  • Fees for tests undertaken to confirm or exclude a diagnosis of Hendra virus are paid by NSW Department of Primary Industries. Extra testing to establish an alternative diagnosis is at submitters’ expense.
  • Contact Customer Service to provide advance notice of your submission and clearly label specimens as Suspect Hendra. A Suspect Hendra warning should also be placed under the lid of the outer package. This will ensure specific biosecurity precautions are undertaken at the laboratory.
  • Pack specimens securely (i.e. double bag and in a rigid container) and forward separately from any other specimens.