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| - The Virus |
| - Bleeders |
News Page |
August 2005 |
Returning to work after viral infectionA question this week has asked about exercise regimes for horses suffering from viral infections. Inevitably, advice will depend on the particular virus, the stage of infection, as well as various matters relating to an individual horse and the type of work it does. As a general rule, no animal should be exercised while in the systemic phase of infection, meaning while the virus is in the body systems, when there will probably be a raised temperature as well as signs of general sickness. These signs may include nasal or ocular discharges, changes in membrane colouration, enlargement of glands (which might also indicate secondary organisms), coughing etc. A common difficulty with lowgrade viruses is diagnosis. An infection can go through the systemic phase without being noticed, especially in horses not in hard training. A loss of form may be the first indication for those that are, although close observation may suggest to an owner/rider that something is wrong. With the more serious viral infections, like herpesvirus (EHV1), there is a profuse watery nasal discharge and the horse tends to constantly clear its nose. Temperatures are usually elevated and it is not uncommon to see a slight yellowing of the mucus membranes (may be quite marked) – due to liver involvement. All this may amount to a slightly technical answer to the question being posed, but any advice has got to reflect the stage of illness and an objective decision will depend on the condition of the individual horse, as there cannot be a blanket formula to cover all situations.
ExerciseOnce the systemic phase of infection has passed, exercise can be resumed, but the way this is managed may well decide whether or not the horse relapses, or picks up another infection. In one EHV1 infection I experienced, there was every indication that the hearts of a significant number of horses were affected. While the suspicion existed that this may have been caused by a complicating second virus, any indication of heart involvement means a horse could not be exercised until this problem was overcome – may only require time and patience. Recovery would have to be gauged by an experienced vet, based on the animal’s ability to cope with even minimal work. A sudden increase in heart rate after trotting, say 20 metres, would act as a warning; meaning it would be dangerous to do anything more. The return to a normal rate would also then be significant.
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In my experience, however, such events do not normally leave horses with permanently damaged hearts and the organ will usually return to normal within weeks of the infection abating. That is, as long as the horse is allowed rest while recovering; inevitably, exercise while the heart is affected could prove fatal. Also, should there be residual conduction problems (irregular beats) after recovery, expert advice would be needed as you are then dealing with a clinical problem on which it would not be possible to generalise. Another possible consequence of viral infection is atrial fibrillation, which may occur because a sick horse (not seen as being sick) is subjected to strenuous work. This particular condition can be treated and the horse will usually return to full normality, perhaps in six months or so to allow the heart muscle time for full recovery. Many such horses win races, or whatever, afterwards. The best advice is to gauge progress on an individual animal and its response to gentle exercise. If there are any signs of distress, like rapid breathing, sudden increase in heart rate, then the horse is doing too much. If to be ridden, go for a gentle walk and stay out for as long as he is enjoying himself and giving no indication of tiredness. Exercise is increased gradually from there, but never sweat a horse in the recovery stages and increase the exercise slowly from day to day. Any indication that an animal is not coping means going back, perhaps taking advice from your vet. Always ensure the animal is receiving effective electrolytes (best in paste form and correctly dosed), as dehydration is a common consequence of systemic infection and needs to be corrected. If not attended to, the coat will remain dry and the horse is unlikely to regain condition, or form. With most mild, even chronic, viral infections, horses can be ridden, although always using good judgement and stopping if any warning signs are shown. The answer to such infections comes in good nursing, feeding, understanding and judgement. Where the situation is complicated by secondary, opportunist organisms, veterinary help will be needed to deal with these. Too often, the return to full athletic fitness is prevented by doing too much too soon. Where individual animals appear to remain infected for unduly long periods, check that there is no underlying cause interfering with resistance, like worms, liver fluke, nutritional deficiency. More specific advice can be given on individual cases on receipt of an email query - - - Peter Gray |
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