[Illustration: FIG. 117.—A case of "lumpy jaw."]

ACTINOMYCOSIS, "LUMPY JAW."—This is an infectious disease that is characterized by the formation of tumors and abscesses (Fig. 117), and the destruction of the infected tissues. The disease is common in cattle and usually affects the bones and soft parts of the head. In the United States, where the disease is known as "lumpy jaw" the jawbone is commonly affected. In European countries the disease frequently involves the tongue, and the term "wooden tongue" is applied to it. The disease may affect regions of the body other than the head. Actinomycosis of the lungs sometimes occurs. Swine and horses may be affected by this disease.

The specific cause of actinomycosis is commonly known as the ray fungus (Fig. 118). This fungus grows on certain plants, and the animal usually contracts the disease by eating plants or roughage that have the fungus on them. Grasses having awns that are capable of wounding the mucous membrane of the mouth and penetrating the gums are most apt to produce the disease. Young cattle that are replacing and erupting their teeth are most prone to "lumpy jaw." Conditions that favor bruising of the jaw and external wounds favor the development of actinomycosis.

The fungus grows in the tissues, causing an inflammatory reaction and destruction of the tissue. The ray fungus can be seen in the diseased tissue or the pus as yellowish, spherical bodies about the size of a grain of sand. Each of these bodies is formed by a large number of club-like bodies arranged about a central mass of filaments.

[Illustration: FIG. 118.—The ray fungus.]

The local symptoms are characteristic (Fig. 117). The tumor may involve the soft tissues of the head. If the jawbone is affected the tumor feels hard and cannot be moved about. Sometimes it is soft and filled with pus. Tumors of long standing may possess uneven, nodular surfaces and fistulous openings. When the tongue is affected, it is swollen and painful, and prehension and mastication of the food may be impossible. When the pharynx is the seat of disease, breathing and swallowing are difficult and painful. Actinomycosis of the lungs may present the appearance of a chronic pulmonary affection. If the disease involves the head and lungs, the animal may become unthrifty and emaciated. In doubtful cases a microscopic examination of a piece of the tumor, or some of the pus, may be necessary.

The treatment is surgical and medicinal. Small, external tumors may be removed by an operation. Sometimes an incision is made into the diseased tissue and a caustic preparation introduced.

The most desirable method of treatment is the administration of large doses of iodide of potassium in a drench, or in the drinking water. The dose is from one to three drachms daily for a period of seven to fourteen days. The size of the dose depends on the size of the animal and its susceptibility to iodism. An animal weighing 1000 pounds may be given two drachms. The treatment is kept up until the symptoms of iodism develop. The condition is indicated by a loss of appetite and a catarrhal discharge from the eyes and nostrils. When this occurs, the treatment should be stopped, and the animal drenched with one-half pound of Epsom salts, and the dose repeated after three or four days. After an interval of two weeks, the iodide of potassium treatment should be repeated if the growth of the tumor is not checked.

EMPHYSEMATOUS ANTHRAX, "BLACK LEG."—"Black leg" is an acute infectious disease of cattle that is characterized by lameness and superficial swellings in the region of the shoulder, quarter or neck. The swellings are hot and painful and usually contain gas.

The specific cause of "black leg" is a rod-shaped, spore-producing germ, the bacillus of emphysematous anthrax (Fig. 119). This germ possesses great vitality, and may live indefinitely in the soil. It has been known to live for years in clay and undrained soils. Young animals that are in high condition are predisposed to the disease.

The germ enters the body through abrasions in the skin and mucous membrane of the mouth and intestines.

"Black leg" is a common disease of young cattle in all sections of the country where cattle-raising is engaged in extensively. Outbreaks of the disease are most prevalent in the early spring after the snow has melted, and in the late summer in localities where cattle graze over the dried-up ponds and swampy places in the pasture. The germs of black leg may be carried from a farm where the disease is prevalent to non-infected premises by surface water. The opening up of drainage ditches through stock-raising communities may be followed by outbreaks of the disease.

[Illustration: FIG. 119.—Bacillus of emphysematous anthrax.]

The symptoms of black leg develop quickly and may terminate fatally in a few hours. These are general dulness, stiffness, prostration and loss of appetite. Lameness is a prominent symptom. The animal may show a swelling in the regions of the shoulder and hindquarters or on other parts of the body. The swelling is very hot and painful at first, but if the animal lives for a time, it becomes less tender, crackles when pressed on and the skin may feel cold and leathery. Fever is a constant symptom. In the highly acute form of the disease nervous symptoms, such as convulsions and coma, occur.

The tissue changes in the region of the swelling are characteristic. An incision into the swelling shows a bloody, dark exudate and the surface of the muscular tissue is dark. Frothy, bloody liquid escapes from the mouth, nose and anus.

The preventive treatment consists in thoroughly draining pastures and yards where cattle run. This measure does not insure cattle against the disease. Cattle that die of "black leg" should be cremated. This should be done at the spot where the animal dies. If the carcass is moved or opened, the ground should be thoroughly wet with a four per cent water solution of a cresol disinfectant and covered with lime.

Vaccination of the exposed or susceptible animals should be practised. On farms where the disease exists it may be necessary to vaccinate the young animals (less than two years of age) once or twice every year in order to prevent the disease. Medicinal treatment is unsatisfactory.

TEXAS OR TICK FEVER.—Tick fever is an infectious disease of cattle. It is caused by an animal organism that is present in the blood, and is conveyed from the animal that is host for the tick fever parasite to the non-infected animal by a tick (Figs. 120 and 121).

[Illustration: FIG. 120.—Cattle tick (male).]

[Illustration: FIG. 121.—Cattle tick (female).]

Tick fever was introduced into the southern portion of the United States through importation of cattle by the Spaniards. Previous to the establishing of a definite quarantine line between the permanently infected and the non-infected sections, heavy losses among northern cattle resulted through driving and shipping southern cattle through the northern States. The specific cause and the part taken by the tick in its distribution were not discovered until 1889-'90. Smith recognized and discovered the specific cause of the disease, and Kilborn and Salmon proved by a series of experiments that the cattle tick was responsible for the transmission of the disease from animal to animal.

The specific cause of tick fever is a protozoan parasite, Piroplasma bigeminum (Fig. 122). It is present in the blood of cattle that are affected with this disease. The natural method of entrance into the body is through the bite of the cattle tick. The disease may be transmitted by inoculating blood containing the parasite into a susceptible animal.

There are two forms of the disease, the acute and chronic.

The symptoms of the acute form of the disease are a high fever, depression, loss of appetite, diarrhoea, dark or bloody urine, staggering gait and delirium. Death may occur within a few days from the time the first symptoms are manifested.

The symptoms of the chronic form of the disease resemble the acute form, but are more mild. The animal is unthrifty and loses flesh rapidly. The bloodless condition of the body is manifested by the pale, visible mucous membrane. Death seldom occurs.

[Illustration: FIG. 122.—Blood-cells with Piroplasma bigeminum in them.]

The most characteristic diseased changes found on post-mortem examination occur in the liver and spleen. The liver is enlarged, and a yellowish, mahogany-brown color. The gallbladder is filled with a very thick bile. The spleen may be several times the normal size and dark colored. When it is cut into, the pulpy tissue may resemble thick, dark blood. The kidneys are pale and the bladder may contain dark or reddish-colored urine.

In the northern States and outside of the quarantined area, the direct or indirect exposure of the affected cattle to southern cattle, and the presence of the cattle tick, Margarophus annulatus, are sufficient evidence to confirm the diagnosis of this disease.

The prevention and control depend on destruction of the cattle tick. In the early history of the disease, shipping and driving of southern cattle into and through the northern States caused outbreaks of tick fever and heavy losses among northern cattle. This finally resulted in the locating of the infected district, and the establishment of the Texas-fever quarantine line in 1891 by Dr. D. E. Salmon.

Previous to this time Kilborne and Salmon proved that the cattle tick was essential to the spread and production of the disease. A further study of the life history of the tick resulted in the discovery that it could not mature unless it became a parasite of horses, mules, or cattle. This has led to the eradication of the tick in certain sections of the South, by not allowing cattle access to a pasture or lot for a certain period, and by freeing the animals from ticks by hand-picking, dipping and smearing.

The immunization of cattle that are shipped into an infected district for breeding purposes is often practised. Immunity is obtained by introducing the P. bigeminun into the blood, either by placing a few virulent young ticks upon the animal, or by repeated inoculation with a very small quantity of virulent blood.

QUESTIONS

1. Give the cause and treatment of actinomycosis.

2. Give the cause and treatment of emphysematous anthrax.

3. Give the cause of tick fever; distribution of the disease and methods of control.