Except as a sequel to acute bronchitis, the chronic form is seldom met with. It differs from it in the absence of fever, the persistence of the cough, and the character of the matter coughed up. Slight causes are sufficient to aggravate the symptoms which are assumed to be due to the morbid irritability and lessened calibre of the small air-tubes by reason of the thickening of their lining membrane. The subjects of it are easily fatigued and their value much depreciated.

Symptoms

These are in some respects the same as in acute bronchitis, but modified in intensity, thick wind and premature fatigue being most noticeable under exertion. There is at the same time an inaptitude for putting on flesh and a want of bloom in the coat. The cough, although less frequent than in the acute form, is much increased in certain conditions of weather, as where cold and wet follow upon a period of dryness and sunshine. It is also provoked by passing from a warm stable into the cold atmosphere without. Horses affected with chronic bronchitis are mostly heard to cough while feeding, and especially if the food is given dry.

Treatment

Treatment may ameliorate the symptoms, and, with care, the subject of it may perform useful work; but it is seldom that anything like a radical cure is effected. Occasionally a young horse, under exceptionally favourable circumstances, will appear to grow out of it, but a trifling ailment is sufficient to bring it on again.

Careful dieting with linseed and damp food should be observed, avoiding all forage with the least suspicion of must or dustiness. The occasional but not habitual use of certain drugs has a beneficial effect. The agents most recommended are myrrh, soap, camphor, squills, carbonate of ammonia, digitalis, and tar in the form of bolus. Iodide of iron and arsenic are also employed with apparent good results.