Peter Gray, Equine Veterinary Surgeon, Expert Witness

- The Virus

- Bleeders

Respiratory Disease

It is important to know if a chronic disease problem is an allergy or not. If it is an allergy, the critical need is to keep the horse away from the source, but many cases are not clear cut and efforts to increase ventilation, for example, may not suit particular horses and can cause chronic breathing problems due to sinus infection or infection of other areas of the respiratory system.

The source of the allergy needs to be found, be that due to organisms in hay or straw, or other allergens in the immediate environment. Where total removal isn't possible, medication may become necessary and your vet will advise you on that.

Hay Quality

It needs to be appreciated that a great deal of apparently clean hay contains organisms and current weather trends mean that it has become increasingly difficult to make hay without rainfall between cutting and baling. When judging hay, it is important to be very critical and assess by smell for the presence of dust. When in doubt, it's always possible to have samples analysed.

Dusty hay will irritate the respiratory passages of even non-allergic horses.

Chronic Respiratory Infection

The observation can be made that much chronic respiratory infection is an expression of management error, be this evident or not; and any infection may gain virulence and spread widely when horses meet at competitions and events.

Because of the demands placed on the respiratory system, infection is a common consequence where athletic animals get wet, are dehydrated or kept in unsuitable stables. Stabling conditions are critical for horses that spend most of their day indoors. Horses like clean air and conditions that allow the retention of body heat.

Drafty buildings lead to weight loss resulting from the increase in metabolic rate needed to retain body temperature. They promote infection by lowering resistance and open airflows encourage its dissemination.

It is interesting to compare the attitudes to this that exist on both sides of the English Channel. In France, a warmer country, internal stabling airflows are very simply, but basically, different. From work ponies high in the Alps to racehorses in the yards of Chantilly, through and through ventilation is not commonplace. Escaping air is channelled into a loft space, or similar, and does not flow from door to back wall, thus making drafts inevitable. The same basic difference exists in the use of barns.

An aside to this is that the incidence of low grade viruses is, rightly or wrongly, considered far less in France; and there is anecdotal evidence to support this. As a direct consequence, the use of routine blood tests is far less common in France.

All infectious organisms run a course marked by contact, incubation, infection and recovery. This should be within definite limits, but the cycle won't be very different from influenza, lasting a few weeks at most, or something as protracted as strangles. Where low grade infections persist for long periods, questions arise about management factors like feeding, hygiene, stabling etc. In these cases, lowered resistance may be allowing re-infection or serial infection with different organisms.