Attention has again been drawn to this subject through the bleeding episode suffered by Best Mate, the triple Gold Cup winner, after working on the gallops just a week before he was due to defend his title. Some of the comments that made their way into the press afterwards signify the lack of understanding that exists, even in professional cirlcles.

As is well known, EIPH, or exercise induced pulmonary haemmorhage, is bleeding from the lungs as a result of exercise. It is possible to have bleeding from other parts of the respiratory tract, like the nasal passages or the gutteral pouches, but the specific problem highlighted by Best Mate is due to a problem in the lungs, brought on by exercise; the blood makes its way to the trachea and, quite often, to the nostrils via the nasal passages. It is seen as a very common condition to the extent that most racehorses are expected to suffer it during the course of a racing career.

What causes this?

The immediate cause is rupture of a blood vessel while breathing at an accelerated rate. The condition is unlikely to occur at rest, though theoretically possible. The greater demand for oxygen at exercise means gradual expansion of the lungs to the full of their capacity. The source of the damaged blood vessel is usually the upper part of the lungs and the volume of blood has, on occasion, been thought to be the cause of death for an animal that has dropped suddenly in the course of, or after, a race. Many such horses are found to have blood in their lungs post mortem.

Is it possible to get bleeding from lungs that have suffered no previous damage? While horses may bleed from non-infected, normal lungs, the most likely cause then would be too great an oxygen demand in an unfit animal. Clinically, virtually all bleeders (not only repeaters) show evidence of lung pathology, reflecting a reduction in available breathing space that means either current, or chronic on-going, disease. Thus, when the demand for greater oxygen intake arises, the lungs are unable to provide it. They cannot expand as nature designed and a strain is placed on the system that results in the rupture of fragile vessels.

Detecting Lung Damage

The simplest, most effective and economical way to detect pre-exisiting lung damage is with a stethoscope. There is virtually always an increased resting respiratory rate, though it may be barely perceptible to an inexperienced observer. It is usually associated with an increased effort, very often a slight suggestion of a heave line. With a stethoscope, there may be dull areas closed by disease, wheezes and other sounds caused by exudate in the lung alveoli.

Under exercise, all these signs become more evident.

Why is lung disease so common today?

Much of this has been discussed in 'The Virus' section, but there should be no residual lung damage with most known viruses, although the consequence of even lowgrade bacterial pneumonia can be more serious. Here, especially if not treated quickly with an effective antibiotic, areas of lung can be permanently damaged and a reduction in lung space suffered. But lung damage also occurs as a result of allergy, or because of a combination of excessive dirt/dust intake coupled with a reduced ability to clear it away from the system.

Is it Preventable?

To prevent permanent lung damage, quick diagnosis is needed coupled with effective treatment. It is usually a failure to recognise on-going disease that causes chronic problems. In many situations, treatment may only mean elimination of bad hay, environmental control of a stable, or better hygiene. But failure to get rid of an irritant, or stress factor, by affecting the horse's resistance, leads to chronic disease. It could be something as simple as a wet bed, too much through-flow of air. Some infections are so lowgrade they are not recognised and this is a major part of the problem.

Most horses in a yard are likely to suffer if a virus is present, perhaps all with virulent types, and bacterial organisms can be very pervasive, especially if assisted by poor hygiene and poor infection awareness.

Bacterial infection of the lungs in older horses is generally less severe than it would be in foals. If detected and treated with an appropriate antibiotic, most will clear up quickly and completely.

We know from the last thirty years that viruses (and to a lesser extent bacteria) exploit situations where large numbers of horses are kept in yards. The level of exercise may become an added stress. Management factors, like drying-off, assisting rehydration, feeding practices, all play a part in allowing infection to persist, if they are faulty.

Infections are most likely to be spread when horses are out of their stable, except perhaps with organisms spread by coughing, or transmitted on the wind. But any organism that enters the body has a defensive system to surpass before it causes disease. As most affected horses are likely to spend most of their day stabled, it is the conditions within that usually dictate resistance and aid recovery. If we get these wrong, the consequence may be chronic disease and bleeding at exercise is simply an expression of this.

The obvious treatment for bleeding is to promote recovery of the lung tissue by ridding the animal of infection or any other source of respiratory irritation. However, we need to look a lot deeper into the animal than simply confining examination to blood analysis and endoscopy. The whole condition of the lungs needs to be assessed on a regular basis in these situations.

The rational treatment for bleeding is to concentrate on the causes and return the lungs to a state as close to perfection as possible. Bleeding might appear to be prevented by a variety of drugs and treatments. In th USA, Lasix is permitted in some States as a preventative. Its effectiveness is based on the way it influences fluid balance and thus blood volume. It is not curative and the only way to deal with bleeding in the long term is to locate the cause and eliminate it. This is entirely possible in a high percentage of horses, though, in many chronic cases, the condition will have existed for so long the degree of damage is too great to be reversed.

Some really good horses still manage to race despite extensive lung damage. The worst I encountered was Oh So Risky, second in the 1994 Champion Hurdle, though I only encountered him at the request of an owner towards the end of his career. He could still beat lesser horses while on the bridle, that is without maximum ventilation. It was only when that extra effort was asked for he got into trouble. Even if there is no bleeding in such a case, lung capacity is reduced and endurance suffers as a consequence.

Master Oats was a Gold Cup winner in 1995, known to have suffered the same affliction.

Now, it would appear, triple Gold Cup winner, Best Mate, has succumbed to the same pathological processes.