The heart is usually pale except in the spots infiltrated by blood, but it may be mottled with petechiæ and particularly on the endocardium. The pericardial fluid is often red. The blood is at first little altered, but later undergoes marked changes, notably an increase of fibrine (50 per cent.) and a decrease of water (as in Asiatic cholera). There is marked leucocytosis, and distortion of the red globules. Before death it becomes black and incoagulable.
The whole capillary system tends to be relaxed and over-distended (congested).
Incubation. As seen in England the incubation was from four to five days. Four to nine days are claimed by Galtier as the extremes, yet he quotes incubations apparently as short as 12, 24, 36 and 48 hours respectively. A source of fallacy rests in the prevalence of cattle plague in the district and the possibility of infection through unsuspected channels, before the recognized exposure. Something must also be allowed for the greater susceptibility and the larger dose of the poison which would tend to shorten the incubation. Thus the western improved breeds, which suffer a mortality of 80 to 95 per cent. (Refik Bey), and the winter season, when the virus is concentrated in small ill ventilated houses, both tend to shorten the incubation. At the Albert Veterinary College in 1865, Gerlach went direct from the infected stable to the sound one, and in 48 hours several of the cattle in the latter had a manifest rise of temperature. Roloff observed the elevation of temperature in 36 hours after exposure, and Ranpach and Ravitsch as early as 11 hours after the inoculation.
Symptoms. The earliest symptom is abrupt hyperthermia, (104° to 108° F.). This is virtually pathognomonic in a herd or locality in which the disease exists, or in suspected animals presumably coming from an infected region. The temperature usually rises to its height on the third or fourth day, and falls materially when other symptoms are developed. In some instances death supervenes during the high temperature, but in the majority the temperature goes below the normal before death.
Often on the second day, or the third, white epithelial eruptions or concretions appear on the inner sides of the lips, closely resembling the eruption of muguet (thrush) and often showing also on the dental pad of the upper jaw and along the gums of the lower. In connection with the high temperature, which is absent in thrush, this symptom is virtually pathognomic. These concretions are more or less abundant in different cases, sometimes so slight as to be easily overlooked, and in other cases encreasing up to the sixth day, and covering not only the lips, dental pad and gums, but extending back over the hard palate, pharynx and gullet. The concretion is as soft as cream cheese, easily detached and leaves a bright red abrasion (not ulcerated) when removed.
By the fourth day there are dry or staring coat, sometimes rigors, sometimes small, accelerated pulse (60 to 120 per minute), some loss of appetite and impairment of rumination, dry muzzle, a general flush of the mucosæ (mouth, vagina, rectum), and deep blood red discoloration of many of the buccal papillæ. There is weariness or debility, the animal remaining down much of the time, also marked thirst, constipation, the fæces covered with mucus or blood, rapidly advancing emaciation, and marked tenderness of the skin, especially of the loins. The head and ears are drooped, saliva drivels, the mouth has a fœtid odor, the eyes weep, and there may be grinding of the teeth. The skin may be hot and the white and delicate parts (udder, teats) suffused by a deep blush. The milk is decreased at first and finally completely dried up.
As the malady advances the belly becomes tender, the constipation is succeeded by diarrhœa with much attendant rumbling, the fæces are at first watery, greenish and acid, and later highly offensive, yellowish brown or gray, and alkaline. These become encreasingly profuse, fœtid and liquid, assuming perhaps a pea soup or rice water consistency before death. The sphincter, at first firm and quickly responsive, finally undergoes permanent relaxation, with constant exposure of the dark red mucosa.
When the disease is fully established the respirations often become highly characteristic. There is not the sudden catching and shortening of the inspiration as in pleurisy, but a sudden closure of the glottis with an audible clicking sound in the course of the expiration, and, after a perceptible interval of holding of the breath, the expiration is resumed with or without an accompanying moan. This phenomenon is so characteristic as to be largely diagnostic. Whether it is due to abdominal pain roused by the sudden forward movement of the diaphragm, or to nervous disorder alone, it is a valuable symptom always to be looked for. It further explains the interlobular emphysema usually met with in the lungs in this disease.
In the more violent cases death supervenes from the sixth to the ninth day, but in the indigenous breeds of Eastern Europe and Asia, which represent a survival of the fittest, the great majority suffer mild attacks and recover, and even in newly invaded countries, when the invasion has spent itself and the less susceptible are largely attacked, a fair proportion survive for a longer period and even recover.
In these milder, protracted, or surviving cases the skin symptoms are likely to come out prominently. Chief among these and very constant at the height of the disease is an abundant unctuous exudation which dries on, forming a crust, comparable to what is seen on the skin in the fevers of swine. At different points, notably on the teats, udder, inner sides of the thighs, and arms, and on the neck, lips and face generally, are epidermic concretions having a warty-like appearance, and respectively seated on a very slightly swollen and congested point of the dermis. The deeper layers of these epidermic concretions often soften, so that they have been mistaken for vesicles and pustules, and hence the error by which cattle plague was held to be but a malignant form of cowpox. But these concretions are histologically distinct from vesicles; there is no liquid exudate on the papillary layer raising the epidermis in the form of a little sac, but merely an excessive production of the cuticular cells with abnormally large nuclei, as happens generally to cells in active proliferation, and an admixture with those of spores and mycelium of fungi which have no special significance.