Cause of sporadic disease in horses and humans
HeV is a zoonotic disease, which means it can transfer from animals to people. This new viral diseases has shown itself in Australia, Queensland, in the last years. Since 1994, HeV has been confirmed only 13 times, involving about 45 horses and 7 humans with 4 human deaths confirmed.
The scientific information available on the disease is not complete because of the small number of HeV cases recorded around the world. Research is ongoing in order to find out about the virus and how it is transmitted from flying foxes (fruit bats) to horses. HeV is a cause of sporadic disease in horses and humans, and is not related to equine influenza or rabies. Even if HeV is present in flying fox populations, the risk of horses being infected is very low. Flying foxes do not pose a significant risk in passing the virus directly to people. All human cases of infection appear to have been contracted from acutely ill horses. The few cases of HeV infection in humans have been the result of very close contact with horses infected with the virus especially during the necroscopy. Body fluids or secretions from an infected animal are likely to contain the virus. Incubation period is between five and 16 days. There is no evidence of human-to-human spread of HeV. HeV is normally carried by flying foxes; however, these animals should not be targeted for unnecessary culling. These animals are critical to australian environment. They pollinate the native trees and spread seeds. Without them eucalypt forests, rainforests and melaleucas would not survive.
HeV can cause a broad range of symptoms in horses: it should be considered where there is rapid onset of illness, fever, increased heart rate and rapid deterioration associated with either respiratory or neurological signs. Occasionally horses will survive HeV infection.
HeV is much more likely to occur in a single sick or dead horse rather than in a number of affected horses. In paddock situations to date, the majority of HeV cases have involved one infected horse that died without any companion horses becoming infected. However, on two occasions one or more companion horses have become infected after close contact with the first infected horse prior to or at the time of death.
It appears that HeV has the potential to spread to other horses either through direct contact with infectious body fluids, or through indirect contact with contaminated equipment that could transfer any body fluid from one horse to another. Two incidents in stables (Hendra 1994 and Redlands 2008) have resulted in multiple infections.
The following symptoms have all been associated with HeV cases, but not all of these symptoms will be found in any one infected horse: rapid onset of illness, increased body temperature/fever, increased heart rate, discomfort/weight shifting between legs, depression, rapid deterioration, respiratory distress, neurological signs (head tilting and circling, inability to rise. apparent loss of vision in one or both eyes. There is no treatment, vaccine or cure.
Patients who are sick after exposure to the disease can only be treated symptomatically and are given prophylactic antiviral medication.
Reducing the risk
Take the following steps to reduce the risk of your horses becoming infected with HeV. This advice is based on our current understanding of the virus.
When more information is gathered through research, more specific advice will be available. In the meantime, the following steps are about reducing contact with items that may be contaminated by the body fluids of flying foxes:
- Place feed and water containers under cover if possible.
- Do not place feed and water containers under trees, particularly if flying foxes are attracted to those trees.
- Do not use feed that might be attractive to flying foxes if they are known to be in the area. Fruit and vegetables (e.g. apples, carrots) or anything sweet (e.g. molasses) may attract flying foxes.
- If possible, remove horses from paddocks where flowering trees have resulted in a temporary surge in flying fox numbers. Return the horses after the trees have stopped flowering.
- If removal of horses from paddocks is not possible, try to temporarily remove your horses during times of peak flying fox activity (usually at dusk and during the night).
- Keep any sick horse isolated from other horses, people and animals until you have obtained a veterinary opinion.
- Do not allow visiting horse practitioners (farriers etc.) to work on sick horses. They should only work on healthy horses.
- If there is more than one horse on your property, handle unaffected horses first and then only handle sick horses after taking appropriate precautions.
- Make sure gear exposed to any body fluids from horses is cleaned and disinfected before it is used on another horse. This includes things like halters, lead ropes and twitches. Talk to your vet about cleaning agents and disinfectants to use.
- Wash your hands with soap and water regularly during and after handling multiple horses.
- If in contact with sick horses, shower with soap and shampoo and dress in clean clothes and footwear before handling other horses.
- Seek veterinary advice before bringing any sick horse back to your property.
People have been exposed to HeV while handling infected horses (includeing sick live horses and dead horses at autopsy examinations). A major problem has been handlers not considering HeV at the time, and thus exposure occurring before the horse was diagnosed.
This means that people need to be aware and carefully consider their safety whenever HeV is suspected. HeV can cause a life-threatening illness. You should therefore be cautious with suspected HeV cases and ensure the personal safety of yourself and others:
- In particular, treat blood and other body fluids (especially lung and nasal discharges, saliva and urine) and tissue as potentially infectious and take precautions to prevent any direct contact with, or splashback of, these body fluids.
- Protect all exposed skin, mucous membranes and eyes from direct contact and cover cuts and abrasions with a water-resistant dressing.