Common Diseases of Farm Animals

by Robert Alexander Craig

CHAPTER XXIX

INFECTIOUS DISEASES OF THE HORSE

STRANGLES. DISTEMPER.—This is an acute infectious disease associated with a catarrhal condition of the air-passages and suppuration of the lymphatic glands in the region of the throat. Colts are the most susceptible to the disease. One attack renders the animal immune against a second attack of the disease, but the immunity is not always permanent.

The specific cause, Streptococcus equi (Fig. 113), was discovered by Schutz in 1888. Strangles is commonly spread by exposing susceptible animals to diseased animals, either by direct contact, or by exposing them to the infection in the stable and allowing them to drink or eat food from watering and feeding troughs on premises where the disease exists. The predisposing causes are cold and sudden changes in the weather. For this reason the disease is most prevalent during the late winter and early spring.

[Illustration: FIG. 113.—Streptococcus of strangles.]

The period of incubation varies, usually from four to eight days.

The symptoms at the beginning of the attack are a feverish condition and partial loss of appetite. The visible mucous membranes are red and dry. This is followed by watery nasal secretions that become heavy and purulent within a few days. The inflammation may extend to the larynx and pharynx.

The glands in the region of the jaw become hot, swollen and painful, and the animal may be unable to eat or drink. The swelling and inflammation of the throat, and the heavy, pus-like secretions that accumulate in the nasal cavities, cause difficult respirations. After a few days the abscesses usually break, and the symptoms are less severe. If the abscesses break on the inside of the throat, the discharge from the nostrils is increased.

The disease may be accompanied by an eruption of nodules, or vesicles on the skin, or nasal mucous membrane.

In severe and chronic cases multiple abscesses may form. This complication is indicated by emaciation and weakness. Such cases usually terminate in death. Severe inflammation and swelling in the region of the throat may terminate in strangulation and death. The death-rate is from one to three per cent.

The preventive treatment consists in using all possible precautions to prevent the exposure of susceptible animals and practising the immunization of exposed animals. The curative treatment is principally careful nursing. Rest, a comfortable stall, nourishing feed and good care constitute the necessary treatment for the average case of distemper. When the abscesses become mature, they should be opened and washed with a disinfectant. Steaming the animal several times daily relieves difficult breathing and the irritated condition of the mucous membranes. In case the abscesses do not form promptly and the throat is badly swollen, a blistering ointment or liniment may be applied. Bitter and saline tonics, the same as recommended in the treatment of indigestion, may be given with the feed.

INFLUENZA (CATARRHAL OR SHIPPING FEVER).—This is a well-known acute infectious disease of solipeds. It is characterized by depression, high body temperature and catarrhal inflammation of the respiratory and other mucous membranes.

Several epidemics of influenza have occurred in the United States. The most serious epidemic occurred in the latter part of the '70's, and the last one in 1900-'01. Influenza is present in the principal horse centers in a somewhat attenuated form.

The specific cause of the disease has never been determined. The virus is present in the expired air, nasal secretions and excreta. Close proximity to a diseased animal is not necessary in order to contract the disease. Stables may harbor the infection, and it may be distributed by such disease carriers as blankets, harness, clothing of the attendant and dust.

The predisposing causes are cold, exposure and changes in climate. When the disease appears in a country, it is first present in the large cities, and from there it is scattered to the outlying districts. The period of incubation is usually from four to seven days.

The early symptoms of the disease are a high fever, marked depression and partial or entire loss of appetite. The horse usually stands in the stall with the head down and appears sleepy. The visible and respiratory mucous membranes are inflamed, the respirations are quickened and the animal may cough. The eyes are frequently affected, the lids and cornea showing more or less inflammation. The digestive tract may be affected. At the beginning, colicky pains may be present and later constipation and diarrhoea. Symptoms of a serious nervous disturbance are sometimes manifested.

The limbs usually become swollen or filled. This disappears as the animal begins to improve. Pregnant mares may abort. The death-rate is low.

The treatment required for the sick animals is largely rest, a light diet and a comfortable, clean, well-ventilated stall, free from draughts. Windows in the stall should be darkened. If the stable is cold, the body of the animal should be covered with a blanket and the limbs bandaged. Two ounces of alcohol and one drachm of quinine may be given three or four times daily. Small doses of raw linseed oil may be given if necessary.

Horses that are exposed to cold, wet weather or worked after becoming sick, frequently suffer from pneumonia, pericarditis, gastro-enteritis and other diseases. Such complications should be given prompt treatment.

It is very advisable to give a protective serum to horses that are shipped or transported long distances, and exposed to the disease in sale or transfer stables.

GLANDERS, FARCY.—This is a contagious and infectious disease of solipeds that is characterized by the formation of nodules and ulcers on the skin, nasal mucous membrane and lungs.

Although glanders is one of the oldest of animal diseases, it was not until 1868 that its contagious character was demonstrated. The disease is widely distributed. It became more prevalent in the United States after the Civil War. The vigorous control measures practised by the State and Federal health officers have greatly decreased the percentage of animals affected with glanders. At the present time the disease is more often met with in the large cities than in the agricultural sections of the country.

[Illustration: FIG. 114.—Bacillus mallei.]

The specific cause of glanders is the Bacillus mallei (Fig. 114). This microorganism was discovered in 1882. It is present in the discharges from the nasal mucous membrane and the ulcers. These discharges may become deposited upon the feed troughs, mangers, stalls, harness, buckets, watering troughs, drinking fountains and attendants' hands and clothing. Healthy horses living in the same stable with the glandered animals may escape infection for months. It is usually the diseased animal's mate, or the one standing in an adjoining stall, that is first affected. Catarrhal diseases predispose animals to glanders, as the normal resistance of the mucous membranes is thereby reduced. The most common routes by which the germ enters the body are by way of the digestive and respiratory tracts. It may enter the body through the uninjured mucous membranes of the respiratory tract and genital organs, or through wounds of the skin.

The period of incubation may be from a few to many days.

The symptoms may be acute or chronic in nature. The acute form pursues a rapid course. It is frequently seen in mules and asses, and it may develop from the subacute or chronic form in horses. When the disease is acute, the animal has a fever, is stupid, does not eat, and may have a diarrhoea. In this form the lymphatic glands suppurate, the animal loses flesh rapidly and dies in from one to two weeks.

[Illustration: FIG. 115.—Nasal septum showing nodules and ulcers.]

The chronic form is the most common. It develops slowly and lasts for years. The early symptoms of the disease (chilling and fever) usually escape notice. The first visible symptom is a nasal discharge of a dirty white color from one or both nostrils. This is usually scanty at first, and intermittent, but later becomes quite abundant. The discharge is very sticky, and adheres to the hair and skin. The most frequent seat of the disease is in the respiratory organs, lymph glands and skin. Nodules and ulcers appear on the nasal mucous membrane (Fig. 115), but they may be so high up as to escape notice. The ulcers are very characteristic of the disease. They are angry looking, with ragged, raised margins, and when they heal leave a puckered scar. The submaxillary glands may be enlarged, and at first more or less hard and painful, but later they become nodular and adhere to the jaw or skin. Nodules and ulcers may form on the skin over the inferior wall of the abdomen and the inside of the hind limbs and are known as "farcy buds." Lymphatic vessels near these buds become swollen and hard. The animal loses flesh rapidly, does not withstand hard work, and the limbs usually swell.

It is sometimes difficult to diagnose the disease. The ulcers on the nasal mucous membranes and elsewhere are very characteristic, and when present enable the examiner to form a diagnosis. In cases of doubt, a bacteriological examination of the nasal discharge may be made, or we may resort to one or several of the various diagnostic tests. The Mallein test is quite commonly used. The sterilized products of a culture of the B. mallei are injected beneath the skin of the suspected animal. This causes a rise in body temperature and a hot, characteristic swelling at the point of injection in glandered animals.

[Illustration: FIG. 116.—Streptococcus pyogenes equi.]

Treatment is not recommended at the present time. Nearly all of the States have laws which aim to stamp out the disease wherever found by killing all affected animals, and thoroughly disinfecting the stables, harness and everything which has been near the animal. Diseased animals should be carefully isolated until slaughtered, and all animals exposed to them should be subsequently tested for glanders.

CONTAGIOUS PLEUROPNEUMONIA (STABLE PNEUMONIA).—This is an infectious disease of solipeds that usually results in a fatal inflammation of the lungs and pleural membrane.

Many writers have described this disease as associated with influenza, but it is frequently seen as a separate disease, usually involving only the lungs and pleurae. It is prevalent in several parts of the United States, more particularly the horse centers or large markets, where it appears in the form of epidemics. In several of these localities it is known as western or stable fever.

The specific cause is not definitely known. The Streptococcus pyogenes equi (Fig. 116) is very commonly present. This germ grows in the diseased tissues. The disease is spread by direct or indirect contact, as when well or susceptible animals are placed in the same stable with an animal affected with the disease, or in stalls which have recently held diseased animals.

The period of incubation is from four to ten days following exposure.

The symptoms are those commonly seen at the beginning of an attack of simple pneumonia and pleurisy. They consist of chills, high fever, cough, depression, difficult and labored breathing and loss of appetite. The disease usually runs a course of from one to three weeks. The death-rate is thirty per cent or more.

The treatment is mainly preventive. Stables where horses having pleuropneumonia have been kept should be cleaned and disinfected by spraying the floors, stalls and walls with a four per cent water solution of a cresol disinfectant. It is advisable to subject all newly-purchased animals to a short quarantine period before allowing them to mix with the other animals in the stable. Exposed animals may be given a protective serum.

The curative treatment is the same as recommended for the treatment of simple pneumonia and pleurisy.