FOWL CHOLERA.—This is a highly infectious disease of all species of poultry, that is characterized by weakness, depression and yellowish colored excrement.

The specific cause of fowl cholera is the Bacillus avisepticus (Fig. 123). This microorganism is transmitted to the healthy birds by the feed, or water becoming contaminated with the discharges from the diseased birds. According to Salmon, the period of incubating varies from four to twenty days.

The early symptoms are a falling off in appetite, high fever, dulness, diarrhoea and weakness. The affected bird becomes drowsy, the head is drawn toward the body, and it may remain asleep for long periods at a time. Salmon states that the general outline of the sick bird becomes spherical or ball-shaped.

[Illustration: FIG. 123.—Bacillus avisepticus.]

The disease is usually highly fatal. In the acute form the larger portion of the flock may die off within a week. In the subacute and chronic forms, the birds become greatly emaciated, and a few die off weekly through a period of a month or longer.

The tissue changes occurring in the disease are inflammation of all or a few of the internal organs. Ward states that the most characteristic lesion of fowl cholera is the severe inflammation of that portion of the small intestine nearest to the gizzard. Small hemorrhagic spots may be found on the heart and other organs.

The treatment is both preventive and curative. The preventive treatment consists in quarantining newly purchased birds until we are satisfied that they are free from disease. The occasional disinfection of the poultry houses and runs is highly important. Cleaning the poultry house by removing the floor, roosts, or any part of the house for the purpose of removing all filth, and spraying the interior with a three per cent water solution of a cresol disinfectant, should be practised. Lime should be scattered over the runs, or the yards immediately about the house. The above preventive measures form an important part of the care and management of the flock. The carcasses of the dead birds should be burned. It is advisable to kill all birds that are fatally sick.

All of the flock should be given antiseptics with the feed and water. Four ounces of a water solution of copper sulfate, made by dissolving one-quarter pound of this drug in one gallon of hot water, may be added to each gallon of drinking water. Frequent disinfection of the drinking fountains, feeding places and houses should be practised.

DISEASES RESEMBLING FOWL CHOLERA.—There are a few diseases, such as septicaemia, limber neck and infectious enteritis, that are sometimes mistaken for fowl cholera. These diseases are caused by different microorganisms that may be found in the digestive tract and air-passages of healthy birds, insanitary conditions and decomposed feed, especially meat. It seems that under certain conditions, such as insanitary quarters and birds that are low in constitutional vigor and weakened from other causes, certain germs may become disease-producers. The death rate from mixed infections is very heavy in poultry.

The symptoms vary in the different cases. The disease may be highly acute, as in limber neck, or chronic, extending over a period of a week or more. Diarrhoea is not a prominent symptom in the majority of cases.

The post-mortem lesions vary from a hemorrhagic to a chronic inflammation of the different body organs and serous membranes.

The treatment is preventive. A frequent cleaning and disinfecting of the poultry house and surroundings, avoiding the feeding of spoiled feed, or allowing the drinking fountains and feeding places to become filthy, are effective preventive measures. Sick birds should be either isolated and quarantined, or destroyed. Antiseptics may be given with the feed and drinking water.

AVIAN DIPHTHERIA (ROUP).—This infectious disease of poultry is especially common in chickens. It is characterized by a catarrhal and diphtheritic inflammation of the mucous membranes of the head.

The specific cause of roup has not been determined. The disease-producing germs are present in the discharges from the nostrils, eyes and mouth, and the body excretions of sick birds. Birds having a mild form of roup, or that have recently recovered from it, are common carriers of the disease. The disease is usually introduced into the flock by allowing birds exposed at poultry shows, or recently purchased breeding stock from an infected flock, to mix with the healthy birds.

The predisposing causes are very important factors in the development of roup. Cold, damp, draughty, poorly ventilated poultry houses cause the disease to spread rapidly and become highly acute.

The symptoms differ in character in the different outbreaks of the disease. Usually the first symptoms noticed are sneezing, dulness, diminished appetite and a watery discharge from the nostrils and eyes. Later the eyelids may become swollen and the nostrils plugged by the discharge from the inflamed membranes. If the mouth is examined at this time, an accumulation of mucus and patches of diphtheritic or false membranes are found. In the acute form of roup the false membranes and yellowish, cheesy-like material accumulate on the different mucous membranes, and interfere with vision, breathing and digestion. The affected bird becomes thin and weak. The death rate is very high in this form of the disease.

The preventive treatment consists in quarantining birds that have been purchased from other flocks, and that have been exhibited, for a period of three weeks. A careful examination of the mouth should be made. If a catarrhal discharge from the nostrils and false membranes is present, prompt treatment should be used. A sick bird should be held in quarantine for several weeks after it has recovered, and receive a thorough washing in a two per cent water solution of a cresol disinfectant before allowing it to mix with the healthy birds.

The medicinal treatment consists in removing the discharges from the nostrils and eyes with pledgets of absorbent cotton that are soaked with a four per cent water solution of boric acid. Among the common treatments mentioned are boric acid and calomel, equal parts by weight, blown into the nostrils and eyes with a powder blower. Water solutions of boric acid, potassium permanganate and hydrogen peroxide are recommended. Liquid preparations are applied with pledgets of cotton, oil cans, or atomizers.

Many recoveries can be obtained with careful treatment. It is usually most economical to kill the severely affected birds. Many poultrymen dispose of the entire flock as soon as the disease makes its appearance, and clean and disinfect the premises before restocking.

CHICKENPOX.—In some sections the disease appears in another form, known as chickenpox (contagious epithelioma), in which nodules form on the skin along the base of the comb and other parts of the head, or both forms may be met with in the same flock. The nodules should be treated with vaseline, or glycerine ointments containing two per cent of any of the common antiseptics or disinfectants.

ENTERO-HEPATITIS. "BLACKHEAD."—This is a very fatal disease of young turkeys. Grown turkeys and other fowls are not so susceptible to the disease. It is characterized by an inflammation of the liver and intestines, especially the caeca.

The specific cause is a protozoan microorganism, Amoeba meleagridis. Adult fowls and turkeys may act as carriers of the germ, and the young turkeys become infected at an early period.

The symptoms are diminished or lost appetite, dulness, drooped wings, diarrhoea, weakness and death. When the disease becomes well advanced, the head and comb become dark.

The course of the disease is from a few weeks to three months. Very few of the young turkeys survive.

The treatment is almost entirely preventive. The same precautionary measures for the prevention of the introduction of disease into the flock, recommended in other infectious diseases, should be practised. Turkeys that survive should be disposed of. As chickens may harbor the disease-producing germs, we should not attempt to raise turkeys in the same quarters with them. Eggs should be obtained from disease-free flocks. Wiping the eggs with a cloth wet with fifty per cent alcohol may be practised. The same recommendations regarding the cleaning and disinfecting of the quarters described in the treatment of fowl cholera should be practised.

If an outbreak of the disease occurs in the flock all of the sick birds should be killed, and their carcasses cremated. Moving the flock to fresh runs and the administration of intestinal antiseptics are the only effective lines of treatment.

AVIAN TUBERCULOSIS.—Tuberculosis of poultry is a serious disease in some countries. Poultry usually contract tuberculosis by contact with a tubercular bird, and not from other domestic animals and man.

The symptoms are of a general character, such as emaciation, weakness, wasting of muscles and lameness. Tubercular growths may appear on the surface of the body.

If we suspect the presence of the disease, it is advisable to kill one of the sick birds and make a careful examination. The finding of yellowish, white, cheesy nodules or masses in the liver, spleen, intestines and mesenteries is strong evidence of tuberculosis. A bacteriological examination of the tissues may be necessary in order to confirm the diagnosis.

The same methods of treatment as recommended in tuberculosis of other domestic animals may be used in eliminating the disease from the premises and flock. This consists in killing and cremating all birds showing visible symptoms, moving the apparently healthy portion of the flock to new quarters and wiping the eggs with alcohol. The old quarters should be cleaned, disinfected, and then allowed to stand empty for several months, when we should again spray with a disinfectant, and scatter lime over the runs. If the cleaning and disinfecting have been thorough, we may safely turn young or healthy birds into the old quarters. All possible precautions against carrying the infection to the healthy flock must be observed.

QUESTIONS

1. Give the cause and treatment for fowl cholera.

2. What diseases resemble fowl cholera? Give the treatment.

3. Give the symptoms and treatment for roup.

4. Give the treatment for "blackhead."

5. Give the treatment for Avian tuberculosis.