Name and Definition. The word croup by which this disease is known over the whole of Europe and a great part of America is, essentially Scotch, and is familiarly used in the Lowlands of Scotland to signify—to croak. The disease consists in an acute inflammation or high vascular irritation of the larynx, associated with spasms of its muscles and commonly though not invariably with a firm layer of exudation on the surface of the mucous membrane. In some cases undoubtedly croup is but a form of the contagious pseudo-membranous affection diphtheria, the germs of which grown on a surface freely swept by continuous currents of pure air, retain too much of an ærobic habit to penetrate deeply into the tissues. (See Authors, “Malignancy mitigated by Oxygen,” Medical Record, 1881, p. 673). It does not follow, however, that croup is always due to even a weakened germ. So far as yet appears it may develop independently of any particular pathogenic germ, from some violent local irritant in a predisposed subject. Croup therefore may be treated here as a presumably noninfectious disease. Being a very rare disease in horses its manifestation in ruminants will first be noticed.
CROUP IN THE OX.
Causes. These are not well understood. Low, damp situations would seem most liable, especially if the animals are much exposed at night. So far indeed as can be observed it arises from the same causes as laryngitis. Age affects its development. Croup is mostly seen in animals between six months and a year old, and rarely in those over five or six years of age. The specific cause of the formation of false membranes and of spasms of the laryngeal muscles is a mystery, but to these the susceptible constitution and tissues of young animals appear to predispose. No mere grade of inflammation from the slightest hyperæmia to the highest type of inflammatory action is of itself sufficient to arouse the special phenomena. All of these are seen everywhere but croup may be said to be confined to certain localities and ages.
Symptoms. Unless it supervenes on a pre-existant attack of catarrh, croup is usually as sudden in its outset in the lower animals as in man. An extremely hard croupy cough, or loud, crowing, difficult breathing, loudest in inspiration, is usually the first symptom and appears to seize the animal in an instant and without the slightest premonition. This is closely followed by intense fever, full, hard pulse, 80 to 100 and upward per minute, increase of bodily temperature sometimes to 107.5° F., costiveness and high colored scanty urine. The throat is excessively tender, the slightest touch giving rise to violent paroxysms of coughing, during which the eyes redden and protrude from their sockets, the veins of the skin are gorged, the tongue, dry and livid, is protruded and small portions of the contents of the stomach and white shreds of false membrane are occasionally brought up. Sometimes in the intervals of coughing as well the mouth is constantly open and the tongue protruded and partly covered by a frothy but tenacious mucus. Suffocation appears imminent in many cases and the beast may perish suddenly in this way. On the other hand the threatening symptoms may be present only at certain periods of the day and may be moderated remarkably at others, especially at early morning. If complicated by any chest affection the symptoms are more urgent and the issue more commonly fatal. If associated with a low type of fever, a small, weak pulse, and much prostration, as it tends to be if it continues several days without relief, it has a more fatal tendency. The same may be said of its occurrence epizootically.
Duration. Croup will often run its course and prove fatal in twenty-four to forty-eight hours. Improvement is manifested by the cough becoming less convulsive and painful, by the expulsion through the mouth of shreds of false membrane, and by return of spirits and appetite.
Postmortem Appearances. If the animal has died suffocated, the lungs and right side of the heart will be gorged with blood; if in a stupor (coma), attendant on brain poisoning with venous blood, the veins will be specially engorged. The mucous membrane of the larynx has a more vivid arborescent redness than in ordinary laryngitis but the special feature is the presence of false membranes. These layers of exuded material are almost confined to the air passages. They may extend to the soft palate and nose in an upward direction and to the trachea and bronchial tubes in a downward, but they rarely exist in the mouth, pharnyx, or gullet like the false membranes of diphtheria.
Characters of the false membranes. These are gray or yellowish white, though they may be reddened in patches or streaks. They vary in consistency from that of glairy mucus to a firm layer as of dense fibrine, and become more adherent as they are of older standing. Sometimes they are partially detached, the free end of the shreds floating in the larynx. The deep or attached surface presents redness in points, in streaks, or as ramifications very visible if the membrane is held up between the eye and the light. They vary in thickness from half to a line. Delafond has found these membranes in the lower animals to be mostly formed of fibrine, with a little albumen, and traces of alkaline and earthy salts.
Treatment. This must be prompt and energetic. Wet cloths as hot as the hands can bear, wrapped around the throat and neck, and replaced as they cool, will usually arrest the spasm. If this fails ether or chloroform by inhalation or chloral hydrate by injection may be employed with caution. The action of the bowels must be secured by salines (sulphate of soda ½ to 1 ℔) or oil (linseed oil ½ to 1 pint) and injections of warm water. Sulphate of soda should be thereafter given in half ounce doses twice daily, or nitrate or acetate of potass may be substituted. They are advantageously given in linseed decoction and may be combined with laudanum, (½ ounce), belladonna, or other agent to check the spasms.
A blister (mustard poultice) should be applied at first either to the throat or breast, the windpipe being left untouched lest tracheotomy should be required. Similar applications to the legs are useful.
If suffocation appears imminent tracheotomy should be at once performed (see under Laryngitis). This operation has been depreciated because of the late period at which it has been employed, when the patient was already past all hope, but the resulting wound in the neck is more than counterbalanced by the greater freedom of breathing and the better æration of the blood which tends to obviate the justly dreaded low fever. It often leads to a rapid diminution of the spasms and laryngeal irritation.