Hendra Virus

Hendra Virus

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Hendra virus infection is an emerging disease in Australia. Cases in horses (with zoonotic spread to humans) have been detected recently in Queensland. Veterinarians or owners of horses that may have been recently imported from Australia should be aware of this disease, and notify MAF Biosecurity New Zealand of any suspected cases.

What is Hendra virus, and what are the signs of disease?

Hendra virus is a viral infection found in Australian fruit bats (Pteropus spp.), which occasionally infects horses and people. It is not present in New Zealand, and infection of horses and people is rare in Australia. In horses, it initially causes a high temperature, restlessness and increased heart rate, which can then progress to severe disease. Signs of disease can be variable, and may resemble respiratory disease, neurological disease, or colic. It takes between five and sixteen days after infection with the virus for horses to display signs of disease. Infected horses shed virus in respiratory secretions, saliva, blood and urine, and could be infectious to other horses and people for two days before signs of disease are seen. Most horses that become infected with this disease die rapidly or are euthanased for animal welfare reasons. The average time between onset of clinical signs and death is just over two days.

What is the risk to people who work with horses?

It is extremely unlikely that a horse infected with Hendra virus would be imported to New Zealand, as Hendra is a rare disease and does not appear to be highly contagious. However, humans have been infected with Hendra virus following prolonged or significant exposures to the body fluids (blood, saliva, urine, parturient fluids, respiratory secretions, etc) of infected horses. More than half of the humans known to have been infected with Hendra virus have died (four deaths out of seven known infections). There is no known effective treatment. Therefore, although the risk of exposure to a Hendra virus-infected horse in New Zealand is extremely low, given the high case-fatality rate of human Hendra virus infection, appropriate precautions should be taken when handling horses recently imported from Australia.

What are the appropriate precautions to use when handling a horse recently imported from Australia?

People working with horses should always practise good procedures for hygiene, biosecurity and preventing spread of disease. These include wearing protective clothing, covering cuts and grazes, preventing contact between horse body fluids and your skin, eyes and mouth, practising good stable or paddock hygiene and isolating sick or recently introduced horses from other horses. If a horse is unwell, or an activity that will lead to a high level of exposure to body fluids (such as surgery, dentistry, endoscopy, necropsy) is required, consider whether additional precautions and protective clothing are appropriate.

Are current import measures still adequate?

Hendra is a rare disease, which requires either exposure to fruit bats or close contact with infected horses. Horses must be certified as free from clinical disease on their day of travel to New Zealand, and must come from a property where Hendra virus has not been detected in the last three months. Although horses could be exported while infected but apparently healthy (Hendra virus has an incubation period of up to sixteen days), this situation is very unlikely given the low incidence of disease. Therefore, the current import requirements are adequate to manage the risk of introduction of Hendra virus into the New Zealand horse population.

I have been working with horses or riding horses in Australia. Do I need to do anything special when I return to New Zealand?

Nothing special. Declare any visits to farms, dirty clothing or boots, and equipment used with animals to biosecurity staff at the border, as you usually would.

What changes should veterinary practitioners make to their practices involving horses?

• Before examining a horse, check with the owner whether it has been recently imported from Australia (within the last thee weeks). If it is a recent import, check the temperature prior to conducting any invasive procedures. In Australia, elevated temperature and heart rate are considered to be clinically useful signs for early warning for suspicion of Hendra virus infection.
• Consider whether you are wearing appropriate personal protective equipment for the task you are undertaking. Procedures that involve exposure to body fluids, secretions or aerosols could be high risk for many zoonotic diseases, not just Hendra virus. Hendra virus can be present in the body fluids of an infected horse for two days before clinical signs of infection can be observed.
• If Hendra virus (or any exotic disease) is the suspected cause of illness in a recently imported horse, call MAFBNZ's exotic disease hotline on 0800 80 99 66. MAFBNZ Incursion Investigators can discuss the case with you and decide whether further testing is required. Cases in Australia have initially been mistaken for other conditions. It is better to call and discuss a possible case early (even if Hendra is not considered very likely) than to take risks.
• We recommend you should also call the exotic disease hotline prior to necropsy of a recently imported horse (e.g. imported from Australia within the last month), so that Incursion Investigators can advise you on whether any particular samples should be collected, or whether you need to take any particular precautions.

What should I do if I suspect Hendra virus?

Contact MAFBNZ immediately on 0800 80 99 66. Postpone any high risk procedures until you have spoken to an Incursion Investigator. High risk procedures are those which expose you to body fluids (blood, urine, respiratory secretions, parturient fluids), including aerosolised body fluids, of the suspect case.

What personal protective equipment could I use?

Veterinarians in New Zealand should have access to personal protective equipment, and should be using it routinely as part of their OSH and infection control practices, to prevent endemic contagious or zoonotic diseases such as salmonellosis and leptospirosis. Hendra virus is transmitted in body fluids of infected animals, so if personal protective equipment is used as a precaution, it should aim to prevent contamination of skin and mucous membranes (including conjunctiva) by horse body fluids, and to prevent inhalation of aerosols or droplets of horse body fluids. For information about occupational safety and health in New Zealand, contact the Department of Labor's Health and Safety office in your area . Information on the equipment recommended in Australia for use with horses in areas where Hendra virus is present can be found in the Queensland Primary Industries and Fisheries Guidelines for veterinarians. A partial list of suppliers of personal protective equipment in New Zealand can be found at the Safeguard Buyers Guide website .

Where can I find further information on the Hendra virus situation in Australia?

Visit the Australian Government Pest and Disease Outbreak Page for information on recent or current outbreaks of livestock diseases or pests in Australia.

The Queensland Primary Industries and Fisheries Hendra Virus portal has a variety of information aimed at both technical and lay audiences.

What is the history of Hendra virus in Australia?

Hendra virus was first reported in 1994 in Australia and belongs to the family of Paramyxoviridae. There have been only 13 confirmed outbreaks in Australia since the virus was discovered, affecting about 40 horses and about 7 humans. Horses, guinea pigs, cats and humans are susceptible to the virus, but natural infection has only been detected in bats, horses and humans.

Hendra virus has been identified in bats in all areas of Australia, as well as in Papua New Guinea. Fruit bats, which are thought to be the natural reservoir of Hendra virus, are found more commonly in the eastern and northern coastal regions of Australia. The exact nature of the interaction that causes the spillover of infection from bats to horses is not known, however spillover of infection into horses appears only to happen in paddock situations where fruit bats are present.

To date, all cases of Hendra virus infection have been on properties in Queensland or northern New South Wales. However, due to the wide distribution of fruit bats, and the movement of horses to events throughout the country, the disease could be found in other areas in the future.

Hendra virus infections cause vasculitis and thus can mimic a broad range of clinical signs in horses, including colic. The initial phase of infection in involves acute hyperthermia and increased heart rate and discomfort (expressed by weight shifting between legs). Affected animals usually progress to depression and severe clinical disease, primarily presenting with either respiratory or neurological signs. The average time between development of clinical signs and death is just over two days.

Signs that have been seen in infected horses include:

• Respiratory: pulmonary oedema, respiratory distress, nasal discharge (clear, progressing to stable white froth or blood stained froth), weakness, collapse
• Neurological: ataxia, altered consciousness, apparent partial or complete blindness, head tilt, circling, myoclonic spasms, urinary incontinence, recumbency with inability to rise, facial paralysis, hypermetria
• Other: Congestion of oral mucous membranes, muscle tremor, facial oedema, anorexia, colic-like symptoms (quiet abdominal sounds), stranguria, straining to defecate.

The incubation period after exposure is usually in the range of 5 - 16 days in horses. Infections in humans have occurred as a result of very close, unprotected contact with infected horses since the virus is found in equine body fluids such as respiratory secretions, saliva, blood and urine. In an infected horse, virus may be found in secretions up to two days before the onset of clinical signs. It is important to note that Hendra virus has a low infectivity, but a high case fatality rate in horses and humans.

Hendra virus appears to spread more readily in stabled rather than paddock-managed horses.

Hendra virus is the subject of active research, involving professionals from both veterinary and medical disciplines, in Australia and internationally. Most of the information about this emerging disease that is currently available is taken from descriptive reports of Australian outbreaks.

For further information, visit the Queensland Primary Industries and Fisheries Hendra Virus portal .

For any suspicion of horses infected with Hendra virus: contact MAFBNZ immediately on freephone 0800 80 99 66.

Page last updated: 1 October 2009