With the appearance of the eruption, usually on the second day of illness, the fever as a rule moderates, and on examination of the mouth bullæ of ⅓d. to 1 inch in diameter may be found on the inside of the lips, and cheeks, or on the palate and tongue, with, in many cases, a congested areola, but showing no nodule as in variola. These bullæ may extend to the muzzle, pituitary membrane or pharynx. They burst very soon after their formation, exposing a red base of inflamed corium, with a clearly rounded margin, or, at first, with shreds of the torn epithelial covering. The salivation now becomes more profuse, glairy and even bloody, and there is more active movement of the tongue. When the bullæ have been confluent there are formed extensive red patches denuded of epithelium, and the suffering causes a complete but temporary dysphagia. The renewal of the epithelium, however, takes place promptly and may be well advanced in four or five days. Upon the teats the bullæ appear at about the same time but are usually smaller than the buccal, and do not show the thickened base of cow pox. They burst in 36 to 48 hours unless broken earlier by the hands of the milker, forming sores comparable to those of the mouth, which are liable to be kept up by the necessary manipulations in milking.
Upon the feet the eruption shows especially in the interdigital space, at first as vesicles smaller than those of the mouth and teats, leaving erosions and ulcers which extend under the adjacent horn, and upward on the front and back of the pastern. From exposure to mud and filth these are liable to be kept up even longer than those of the mouth and teats, and under neglect the entire hoof is often shed. In sheep and swine the disease may be localized almost exclusively in the feet. Sheep will even walk on the knees.
In young animals and those fed on the milk, the eruption may take place on the intestinal mucosa with violent congestion, diarrhœa and a fatal issue. Aggravated cases may show gangrenous mammitis or abortions.
Mortality and Prognosis. While there are seasons of special pathogenic severity, yet as a rule, the foot and mouth disease is a mild affection and unless neglected, the patients entirely recover in about fifteen days. The pecuniary loss in dairy and feeding cattle has been found to average in Great Britain about $10 per head, and as few animals escape, the consequences are usually very serious. In England the losses from this disease in 1883 reached $5,000,000, in France, those of 1871 were $7,500,000 and in Switzerland, $2,500,000. In Germany, over 7,000,000 animals suffered from 1889–94.
Differential Diagnosis. While a mistake might be made in an isolated case, such a thing should be absolutely impossible where cattle and other animals are collected in herds. The rapid infection of the whole herd, the implication of sheep and swine along with the cattle, and the eruption of the characteristic bullæ on the mouth, feet and udder or on two of these locations to the exclusion of the rest of the body, is not likely to be counterfeited by another disease. An outbreak of gangrenous ergotism in Kansas, Missouri and Illinois in the spring of 1884, was pronounced to be foot and mouth disease by a number of veterinarians, including an expert sent by the Government of Canada. On behalf of the U. S. Treasury I investigated the disease, which caused in many cases sores on the mouths and feet, but it spared all sheep and swine, could not be conveyed to them nor to new born calves by inoculation, and in many cases it caused gangrene of all the tissues, soft and hard, and separation of the limb at a given point, often near the tarsus. The quarantines were raised, the disease made no further extension, and the existing panic subsided.
Infection of Man. The first authentic record of this affection in man we owe to Valentin, who records that during the outbreak in Hesse in 1695 men suffered from inflammation of the gums, tongue and mouth. Michel Sagar says, that in 1764 men who drank the milk were affected with aphtha. In 1828 it was conveyed from animals to men in Bohemia (Nadberny), in Styria (Levitsky) and Wurtemberg (Kolb). In 1834, three veterinarians, Hertwig, Mann and Villain, voluntarily drank a quart each of the warm milk of a cow suffering from this affection. On the second day Hertwig suffered from fever, headache and itching of the hands and fingers. Five days later bullæ formed on the hands and fingers, the tongue, cheeks and lips. In the two others the eruption was confined to the buccal mucosa. Since that time records of the infection of human beings have been very numerous. During the American epizoötic of 1870 I met with the case of a farmer at South Dover, N. Y., who suffered from sore mouth and blisters along the margin of the tongue from drinking the milk. The danger is greatest in children on an exclusive milk diet and who drink it warm. Kolb in 1828, noticed acid vomiting and diarrhœa in such subjects, Hübner observed that beside the buccal eruption such children often suffered from inflammation of the stomach and bowels and that very young children fed on the milk of the diseased cows died. Balfour, Watson and others have noticed similar results in Scotland.
Allbutt saw the buccal eruption in three children in Yorkshire, England, during the local prevalence of the English epizoötic in 1883, and secured information of a number of other cases in the same district.
A number of cases were recorded during 1893 in Germany. A shepherd infected himself by holding in his mouth the knife with which he had pared the diseased feet of sheep, and another workman and a veterinarian had extensive eruptions on the hands after dressing the affected feet. A number of milk-maids were infected by milking, the eruption appearing on the hands, and in one case on the breast. A child fed on the milk of diseased cows, had chill and fever with gastric disturbance, and later an eruption of vesicles on the lips and tongue and between the fingers and toes.
Again, in 1895, during the prevalence of foot and mouth disease in the southern part of Berlin, a considerable number of the milk consumers suffered from fever with the eruption of bullæ on the tongue and buccal mucosa generally, which on early bursting left very painful ulcerations. The acute disease did not last more than five days, but left a sense of great weakness for a time. Virchow, who made an investigation, unhesitatingly pronounced it to be foot and mouth disease.
Cases of infection through butter made from infected milk are on record. A Berlin veterinary student suffered from the buccal eruption and erysipelatoid swelling of the ear, and a German clergyman had in addition a period of chilliness, fever, diarrhœa and pruritus. Similarly Schneider quotes cases determined by infected cheese, and Friedberger and Fröhner, cases caused by virulent buttermilk.