Taking Precautions In the Stable Against Hendra Virus

The deadly Hendra virus first appeared in Australia in September 1994 when trainer Vic Rail, a stable hand and most of his horses fell ill to a mysterious illness. Within days Rail and 14 of his horses were dead. This deadly virus was unknown in the equestrian world and it took some time before researchers were able to pinpoint the possible cause of the disease. The Hendra virus is now known to be akin to the Nipah virus which occurs periodically in Malaysia, Singapore, Bangladesh and neighbouring countries.

A new outbreak which has occurred recently has brought the subject of the virus to the forefront again. There are now strategies in place to deal with the problems and the authorities are quick to step in and assist whenever an outbreak seems possible.

Hendra virus is now believed to be spread by fruit bats (flying-foxes). Fruit bats play a major role in seed dispersal and pollination of native plants. They and their roosting areas are protected by law. Unfortunately it is believed that the bats carry the virus which spreads to horses by way of contaminated food. The virus does not cause sickness in the bats which merely act as hosts to the virus. The disease may be transmitted from horses to humans through infected body fluids such as nasal discharge, urine, blood, etc. Although transmission to humans is said to be rare, four humans have already died from the disease.

So far, the disease has been confined to areas around Cairns in Queensland to northern New South Wales. If you have a horse which appears sick, you need to notify a veterinarian immediately. This virus is not to be taken lightly. Hendra virus is a notifiable disease and the authorities will take steps to assist you in managing an outbreak and coping with the consequences.

Horses show respiratory and neurological symptoms. Some of these symptoms are increased respiration and heart rate, nasal charge, restlessness, muscle twitching, a wobbly gait and an inability to rise. It will be useful for your vet if you are able to give as full an account as possible of your horse's symptoms. Temperature, respiratory rate, mucous membrane status, capillary refill time and dehydration status are statistics that are not hard for the owner to ascertain for him/herself.

The temperature of a horse varies from 37 to 38oC. To take a horse's temperature, insert a thermometer into the horse's rectum. Grease the thermometer if you feel the need. Hold the tail to one side and insert the thermometer gently. Most horses don't show any objection to this indignity. Leave for a minute then take a reading. Digital thermometers will 'bip' once the temperature has been taken.

A horse's pulse or heart rate is approximately 38 beats per minute. The easiest way to measure this is with a stethoscope but you can use your fingers almost as easily. Stand on the nearside (horse's left-hand) shoulder and place the stethoscope on the chest just inside the front leg and in line with the elbow. You may need to move it around until finding a beat. If you look, you should be able to see quite a prominent blood vessel. The pulse can also be found under the jaw up near the throat or on the underside of the horse's dock.

Another test is the capillary refill time which should be 1 to 2 seconds. To measure this, lift the horse's upper lip and press the thumb firmly against the gums for two seconds. The area will now be pale or white. As the blood returns to the spot, it will return to a normal pink colour. This should happen within 1 to 2 seconds.

Dehydration is measured by the 'pinch' test. Pinch the skin on the horse's neck. When you release the skin it should flatten again within a second. The longer the skin takes to return to its normal 'flatness', the greater the amount of dehydration.

The mucous membranes are the linings of the eyelids, the gums and inside the nostrils. The normal colour is a moist pink. Very pale pink, grey, bluish, yellow or bright red are signs of abnormality.

Respiration will vary from 8 to 15 breaths per minute. You can watch the horse's ribcage move in and out with each breath or by placing your hand in front of the nostril, you will be able to feel each breath.

Even if your horses are healthy, it would be sensible to practice working out these factors without the stress of a potentially sick horse to worry you.

If your horse needs to be assessed further, there are currently three types of test applied to show evidence of Hendra virus.

The PCR test is carried out on horses suspected of having the virus. It is also used to monitor horses during a virus incident. The quicker that infection can be detected in an animal the more quickly steps can be taken to treat and isolate sick animals. A positive result to the PCR test means that the horse is infected. Blood samples, nasal or oral swab, urine and tissue sampled can be used for PCR testing.

An indirect ELISA test is used to monitor horses for the presence of antibodies. It is carried out on horses that may have been infected. Results are usually available within 24 hours of the laboratory receiving samples. This is a very sensitive test conducted on blood samples and false positive results are very rare. Successive tests showing as negative indicate that the horse can be regarded as negative for Hendra virus.

The third test is the Hendra virus serum neutralisation test (VNT). This test is conducted on a blood sample and is used to detect antibodies to Hendra virus. This is one of the final tests used before lifting movement restrictions on suspect horses. Test results take 7 to 10 days to be returned. This is regarded as a definitive test confirming whether or not an animal has been exposed to Hendra virus. National policy states that any horse returning a positive VNT test will be humanely euthanised.

The Hendra virus looks like becoming part of 'normal' life. Preventative measures include feeding horses under cover but not under trees likely to be frequented by fruit bats. Don't feed apples, carrots, molasses or any fruit or sweet food likely to attract bats. Practice strict hygiene measures in and around the stable. Wash your hands thoroughly after handling horses. Keep open wounds or sores covered. Don't lend or borrow harness, floats or equipment unnecessarily. This disease can and has killed humans, not just horses. Its potential for damage is immense.