Part 22

In the worst cases death may ensue by the third or fourth day, but in others the diarrhœa is critical and heralds an improvement which goes on to a speedy recovery. In still other cases the bowel troubles continue, the fever does not give way and the privation of food and rapid metamorphosis of tissue produce steady emaciation and fatal marasmus.

A striking feature of the gastro-intestinal disease is the extraordinary susceptibility to laxatives. So much is this the case that I have known of two drachms of aloes proving fatal by superpurgation in a large, mature Percheron horse. It is never safe to use laxatives in equine influenza until one has ascertained whether in the special form of the epizoötic in question the gastro-intestinal organs are or are not especially involved.

Disorders of the eye are so common or constant as to have procured for certain epizoötics the name of pink eye. They set in suddenly, and equally in both eyes, with infiltration of the lids and particularly of the mucosa which is of a more or less deep red, and may bulge between the margins of the eyelids, (chemosis). The flow of tears is profuse, seropurulent matter accumulates at the canthi and in the lachrymal sacs, vision is impaired and there is intolerance of light. The cornea becomes bluish, cloudy or milky white, with a red zone around its margin and, above all, on the adjacent sclerotic. In some cases the aqueous humor becomes turbid or flocculent, and the iris changes its clear, healthy dark lustre for a dull brown or yellow tint. The tension of the globe may be materially encreased. They are readily distinguished from recurrent ophthalmia by the attendant weakness, stupor and hyperthermia, and by their non-recurrence in case the patient survives.

The nervous symptoms are especially manifest in the sudden seizure, great prostration, extreme weakness, profound stupor or lassitude, the staggering gait, in bad cases, insensibility to voice, slap or, it may be, even to the whip, the rigidity of the loins, their insensibility to pinching, the difficulty of turning in a short circle, or of backing. The high fever, disproportionate to the appreciable local lesions, and its sudden improvement at the critical period, the excessive weariness and the disposition to lie down contrary to the habit of other inflammatory chest diseases are further indications.

This may go on to coma, there may be more or less complete anorexia, muscular trembling, paresis, especially of the hind limbs, or delirious manifestations indicating meningitis.

Rheumatoid attacks of the muscles and joints usually appear in the advanced stages of the disease, but may appear earlier. They may occur in any latitude but seem to be especially common in cold, damp, inclement northern regions, and at seasons when climatic vicissitudes are sudden and extreme. These may appear suddenly and disappear with equal rapidity, or they may last for a time during and even after an apparent recovery in other respects. When the joints are involved they usually become engorged with exudates in the synovial membranes.

Lameness in either fore or hind limb may assume an intermittent type developed by exercise and subsiding with rest, evidently bespeaking local arterial embolism, and in such cases it is likely to persist for months.

A tendency to transudations and dropsical effusions is common in severe cases, showing especially in the filling of the legs, but in certain epizoötics, these become strikingly prevalent and have secured for such a special name (epizoötic cellulitis). Apart from the limbs these affect particularly the inferior surface of the chest and abdomen. The swellings are not necessarily hot nor painful nor petechiated as in petechial fever, yet they may merge into that affection or they may become phlegmonous and develop abscess.

Complications of many kinds are to be looked for, pregnant mares may abort; laminitis may set in; the microbes of strangles, contagious pneumonia, cerebro-spinal meningitis, septicæmia, pyæmia, etc., may take occasion to attack the debilitated system, and thus complex diseases and manifestations are developed.

Morbid Anatomy. The lesions may predominate in different organs in different subjects and successive epizoötics. It is a protean disease and may expend its main energy on any one of a number of different organs or systems of organs.

In the slighter cases the lesions are often largely confined to the anterior part of the respiratory organs. The fauces, pharynx, larynx, guttural pouches and nasal mucosa are tumified, congested, red and covered with mucous, and this condition may extend down to the bronchia. In such cases the blood is normal or may coagulate with undue readiness and firmness. The pharyngeal and intermaxillary lymph glands are red and congested in their outer zone.

In the more severe cases the alterations in the blood are perhaps the most constant of the morbid features. The blood is fluid and incoagulable, or the clot is soft, diffluent and black, the red globules are crenated or broken up, and show little tendency to adhere in rouleaux. The escaped hæmatoidin accumulates in masses in the serum in crystalline forms, giving it a high staining power when a line is drawn with it on white paper. Fatty globules also float in the mass. The leucocytes are relatively very much encreased and the red globules diminished. Dieckerhoff found 30,000 and Trasbot 40,000 leucocytes in a cubic millimetre.

The diffluence is not constant. Blood drawn in the earlier stages of the disease, coagulates with extraordinary firmness, influenced, doubtless, by the encrease of the leucocytes, the disintegration of the blood globules, and the liberation of globulins. This serves also to partially explain the early and sudden deaths from coagula in the heart and large vessels, which are occasionally met with. Such clots in the heart are often found adherent to the valvular or ventricular endocardium which at such points shows cloudy swelling, thickening, cell proliferation and even encreased vascularity and granular elevations.

In advanced cases, however, the prominent features are usually acidity, blackness, and incoagulability of the blood, its resistance to oxygen, altered and broken down red globules, free coloring matter, relative encrease of white cells, and, if necropsy has been delayed, the abundance of septic microbes (cocci and bacilli). Petechiæ are abundant on the serosæ especially on the pericardium.

Lesions of the alimentary mucosa are very constant. There may be stomatitis, with tumid follicles and even ulcers (Kowalavsky). In the stomach the right sac has its mucosa thickened, softened, red, congested, petechiated and discolored. The summits of the folds may be ulcerated (Labat). Similar lesions are presented in the small intestines. The agminated glands may show many rounded elevations, with or without open discharging follicles. The mucosa is covered with a muco-purulent material. Otherwise, the small intestines, like the stomach, are usually empty. The large intestines present similar lesions, the nodular elevations often representing the solitary glands, and the masses of ingesta are likely to be dry and indurated, in the earlier stages or semiliquid in old standing cases. The peritoneum may be congested, petechiated and at points infiltrated and usually contains a reddish serum in variable quantity. The mesenteric glands are more or less enlarged and congested.

The liver shows more or less congestion as in other infectious diseases localized in the bowels. It usually has a parboiled appearance, and yellowish gray areas of necrosis may be manifest, or again, fatty degeneration may be present. Petechiæ, and even small blood clots may be found on or beneath the capsule. The pancreas, and, still more, the spleen may be the seat of congestion or engorgement but this is far from constant.

The capsule of the kidney may be petechiated or elevated at points by serous exudate or extravasation. The surface of the organ and of sections show a mottling with darker and lighter areas, and petechiæ and patches of congestion may be found on the bladder and urethra.

The nervous centres exceptionally show meningeal congestions, and exudations, and petechiæ as has been noted of other serosæ.

Lesions of the eye may be confined to the mucosa, or they may extend to the membrane of the aqueous humor, the iris, or even the deeper structures.

Other lesions such as laminitis, bursitis, arthritis, like those attendant on abortion need no special description.

When pulmonary lesions are extensive, the bronchial mucosa is not only softened, opaque and covered with a serous, or muco-purulent discharge, but deeply congested and petechiated. When the chest is opened there is usually an effusion, pale straw, red or bloody and more abundant than in contagious pneumonia. False membranes may exist and show a blackish tint from extravasated blood. The lung fails to collapse and shows on the surface and throughout its substance petechiæ and small black infarctions. In some instances the whole lung is blood gorged, black, almost jelly like, as in acute congestion. In others these are limited infiltrations, concentrated especially in the anterior and lower parts, and almost invariably affecting both right and left lungs. The infiltration is circumscribed in area in comparison with the attendant fever and constitutional disturbance, resembling in this respect, the lesions of contagious pneumonia. It differs however in having a greater tendency to liquid infiltration of the connective tissue, and but for the lack of such tissues in the horse’s lung it would tend to approximate to the lesions of lung plague in cattle. It shows a distinct thickening of the interlobular septa, a tendency to extension to the pleura, and to issue in pleural and subpleural infiltration, and to a more copious effusion into the pleural cavity than in either fibrinous or contagious pneumonia. The lung tissue may be granular and hepatized, but far more frequently it is only splenized, the lung being the seat of a bloody infiltration, yet retaining much of its elasticity and coherence. Portions may be infarcted and black and large areas may have a pale or parboiled appearance, and gangrene is by no means uncommon.

Diagnosis. This is based largely on the suddenness of the attack, its epizoötic character, the numbers attacked in rapid succession, and over a large area as contrasted with contagious pneumonia, the sudden and extreme prostration and weakness, the swelling, watering and discoloration of the eyes, the mildness of the average case, the congestion of the upper air passages, and in the mild cases a comparative immunity of the lungs, the irritability or congestion of the gastro-intestinal mucosa, and the history of the case:—the arrival of the infected horses within a few days from an infected place, or coming through infected channels, or the attack of new arrivals in a previously infected stable, or the known advance of the disease towards the place where the patients are, will usually serve to mark the true nature of the affection.

As a help to correct diagnosis we give below some of the prominent conditions and phenomena of the three forms of lung disease known as fibrinous pneumonia, contagious pneumonia, and the pneumonia of equine influenza:

=Pneumonia=: =Pneumonia=: =Pneumonia=:

Croupous Fibrinous. Contagious, of Equine of Equine Influenza. Animals.

From climatic Slow succession of Rapid succession of vicissitude, cases in the same cases in the same exposure, etc. stable, irrespective stable or locality, Attacks exposed of climate or irrespective of animals only, and all exposure climate or exposure at once

Prevails in inclement Any season: worse in Any season: worse in seasons, spring, inclement season inclement season autumn, (Winter)

Infection from close Infection spreads proximity, contact, widely and rapidly stall, manger, rack, through the air. bucket, trough, etc.: Spread rapid and Spread slow often general