[Illustration: FIG. 101.--_Bacillus bovisepticus_.]
_The symptoms_ vary according to the animal and organ, or organs of the body affected and the violence of the attack. The disease may be acute or subacute. The brain and its membranes, lungs and air-passages and intestines may become affected. The symptoms may be classed under the head of nervous, respiratory and intestinal (Fig. 102), and they may be very unsatisfactory from the standpoint of diagnosis. The history and post-mortem lesions are of most value in the recognition of this disease.
The local conditions, the loss of several animals in the herd and the finding of hemorrhagic lesions in the different body tissues may enable the examiner to correctly diagnose the disease. It is very advisable in order to confirm the diagnosis to make a bacteriological examination of the tissues.
The acute form of the disease is very fatal. Animals that have the subacute form usually recover. The death-rate is between five and fifteen per cent of the herd. The mortality is heavier than this unless prompt preventive measures are taken.
_Preventive treatment_ is of the greatest importance. Cattle that become affected when running on pasture should be moved, or in case a part of the pasture is swampy, we may prevent further loss by fencing off this portion.
Drinking places that are convenient and free from filth should be provided.
Watering troughs and drinking fountains should be cleaned and disinfected every few weeks. For this purpose, use a three per cent water solution of a cresol disinfectant, or a ten per cent water solution of sulfate of iron.
Dusty quarters should be cleaned and disinfected. Dirt floors may be sprinkled with crude oil.
[Illustration: FIG. 102.--A yearling steer affected with septicaemia haemorrhagica, intestinal form.]
When an outbreak of septicaemia haemorrhagica occurs in a herd, both the well and sick animals should be given a physic. Cattle may be given one-half pound of Epsom salts, repeated in three or four days; sheep and hogs from one to four ounces of raw linseed oil. Animals that have the subacute form of the disease may be given stimulants, and iron and bitter tonics.
ANTHRAX, CHARBON.--This is an acute infectious disease affecting many different species of animals. Anthrax is one of the oldest animal diseases, and early in the history of the race it existed as a plague in Egypt. It most commonly affects cattle, sheep and horses. Man contracts the disease by handling wool and hides from animals that have died of anthrax, and by accidental inoculation in examining the carcass of animals that have died of the disease.
_Cause_.--Anthrax is caused by a rod-shaped, spore-producing microorganism, _Bacillus anthracis_ (Fig. 103). It gains entrance to the body by way of the intestinal tract, lungs and air-passages and the skin. The bites of insects play an important part in the distribution of the disease in some localities, but the most common method of infection is by way of the digestive tract, through eating and drinking food and water contaminated with the anthrax germs. The spores of the _B. anthracis_ are very resistant to changes in temperature and drying. They may live for years in rich, moist inundated soils. River-bottom and swampy lands that have become infected with discharges from the bodies of animals sick with anthrax, and by burying the carcasses of animals that have died of this disease, retain the infection for many years. Anthrax is very widely distributed. It is the most prevalent in the southern portion of the United States, especially the lower portion of the Mississippi Valley.
[Illustration: FIG. 103.--_Bacillus anthracis_.]
_The symptoms vary in different cases_, depending on the organs affected, and the virulence and amount of virus introduced. The _apoplectic form_ is very acute. The disease sets in suddenly; the animal trembles, staggers, falls and dies in a convulsion. Blood may be discharged from the nose and with the urine and faeces.
In the _abdominal form_, abdominal pain, diarrhoea, prolapse of the rectum, bloating and doughy swellings in the region of the abdomen occur.
In the _thoracic form_, the symptoms are bloody discharge from the nostrils, salivation, rapid, difficult breathing and swelling in the region of the throat. Local or skin lesions may occur in conjunction with, or independent of, the above forms of disease. These are carbuncles one or two inches in diameter that are hot and tender at first, but later become gangrenous, diffused swellings.
On post-mortem examination the blood is found tarry and dark, and bloody exudates may be found in the abdominal and thoracic cavities. The spleen is soft and two or three times larger than normal. The diagnosis should be confirmed by finding the _B. anthracis_ in the blood and tissues. The death-rate is very high, usually about seventy-five per cent.
_The treatment is preventive._ Animals should be kept away from lots and pastures where deaths from anthrax have been known to occur, unless immunized against the disease. Marshy, swampy land that is infected with the germs of anthrax should be drained and cultivated.
When an outbreak of the disease occurs, all of the animals should be vaccinated. The carcasses of the animals that die should be cremated at or near the place where they die. If hauled or dragged, the necessary precautions should be taken against scattering the infectious material from the carcass, and plenty of disinfectants used. Persons attending the animals should be warned against opening or handling the carcass without protecting the hands with rubber gloves.
_Anthrax vaccine_ should not be used by incompetent persons.
ULCERATIVE STOMATITIS. (ULCERATIVE SORE MOUTH.)--This is an infectious disease of young animals. Pigs from a few days to a few weeks of age are the most commonly affected.
_The specific cause_ of ulcerative sore mouths is the _Bacillus necrophorus_ (Fig. 104). The infectious agent is distributed by the udder of the mother becoming soiled with filth from the stable floor and yards, and by affected pigs nursing mothers of healthy litters. Filth, sharp teeth and irritation to the gums from the eruption of the teeth are important predisposing factors.
_The symptoms_ are, at first, an inflammation of the mucous membrane lining the lips and cheeks and covering the gums. The inflamed parts are first swollen and a deep red color; later, white patches form and the part sloughs, leaving a deep ulcer. As ulceration progresses, difficulty in nursing increases until finally the young animal is unable to suckle. If ulceration of the mouth is extensive, the animal may be feverish, dull and lose flesh rapidly. Portions of the lips, gums and snout may slough off.
The death-rate in pigs is very high.
[Illustration: FIG. 104.--_Bacillus necrophorus_.]
_The preventive treatment_ consists in keeping the quarters and yards in a sanitary condition, and using all possible precautions against the introduction of the disease into the herd. The diseased young and mother should be separated from the herd and the quarters disinfected daily. The mouths of all the young should be examined daily and the diseased animals treated. The ulcers should be scraped or curetted and cauterized with lunar caustic, and the mouth washed daily with a two per cent water solution of a cresol disinfectant. Dipping pigs headforemost into a water solution of permanganate of potassium (one-half teaspoonful dissolved in a gallon of water), twice daily, may be practised if the herd is large.
It is usually most economical to kill the badly diseased animals, as they usually die or become badly stunted.
RABIES, HYDROPHOBIA.--Rabies is an infectious disease affecting the nervous system, that is transmitted by the bite of a rabid animal and the inoculation of the wound with the virus present in the saliva. It is commonly considered a disease of dogs, but because of the disposition of rabid dogs to bite other animals, rabies is common in domestic animals and man.
Rabies is widely distributed, being most prevalent in the temperate zone, and where the population is most dense. It has been excluded from Australia, Tasmania and New Zealand by a rigid inspection and quarantine of all imported dogs.
_The specific cause of rabies_ is probably a protozoan parasite (the Negri bodies present in nerve-cells, Fig. 105). The germ spreads from the wounds through the nerves and central nervous system. The disease-producing organisms are present in great numbers in the nerve-tissue and saliva.
_The period of incubation_ varies from a few days to several months. It is usually from ten to seventy days.
_The symptoms_ differ in the different species. There are two forms of the disease: the _furious_ and the _dumb_. The former is more common.
[Illustration: FIG. 105.--Negri bodies in nerve-tissue.]
_In the dog, the symptoms may be divided into three stages_. The first, or _melancholy stage_, usually lasts from twelve to forty-eight hours. The animal's behavior is altered and it becomes sullen, irritable and nervous.
Sometimes it is friendly and inclined to lick the hand of its master. An inclination to gnaw or swallow indigestible objects is sometimes noted.
Frequently a certain part of the skin is rubbed or licked.
The second, or _furious stage_, may last several days. Violent nervous or rabid symptoms are manifested, and the dog may leave home and travel long distances. The animal usually shows a strong inclination to bite. It may move about snapping at imaginary objects in its delirium, and may bite any person or animal with which it comes in contact. The bark is peculiar, the appetite is lost and the animal becomes weak and emaciated.
In the third, or _paralytic stage_, the dog may present an emaciated, dirty, ragged appearance. The lower jaw may drop, the tongue hangs from the lips and the eyes appear sunken and glassy. Paralysis of the hind parts may be present.
_In the dumb form_, the paralytic symptoms predominate and the disease pursues a short course. Rabies terminates in death in from four to ten days.
_Furious rabies_ is more common in the _horse_. The animal is very nervous, restless and alert. It may attack other animals in a vicious manner, kicking and biting them. The animal does not seem to care to eat or drink, and usually shows violent nervous symptoms, such as biting the manger, rearing and kicking when confined in the stable.
_Cattle_ butt with the horns and show a tendency to lick other animals.
They bellow more than common and the sexual desire is increased. Paralytic symptoms are manifested early in the disease, and the animal may fall when moving about. They soon present a gaunt, emaciated appearance.
In dogs the diagnosis is confirmed by a _microscopical examination_ of the vagus ganglia and that portion of the brain known as Amnion's horn, and the finding of Negri bodies in the nerve-cells. In case a person is bitten by a dog, the animal should be confined until the disease is well advanced and killed or allowed to die. The head should then be removed and forwarded to the State laboratory, or wherever such examinations are made.
_The treatment_ is preventive. Wherever an outbreak of rabies occurs all dogs should be confined on the owner's premises or muzzled. All dogs running at large without muzzles should be promptly killed. A heavy tax on dogs, and the killing of all dogs not wearing a license tag, would prevent the heavy financial loss resulting from rabies, and the ravages of wandering dogs in the United States. In countries where the muzzling of dogs is enforced during the entire year, rabies is a rare disease.
FOOT-AND-MOUTH DISEASE.--This is a highly contagious and infectious disease of cattle, sheep, goats and swine. It is characterized by the eruption of vesicles on the mucous membrane lining the mouth, the lips, between and above the claws and in the region of the udder and perineum. Man may contract the disease by caring for sick animals; or by drinking raw milk from a sick cow. Babies are most susceptible to infection from milk.
Foot-and-mouth disease was introduced into eastern Europe from the steppes of Prussia and Asia near the end of the eighteenth century. It was introduced into England about 1839, and in 1870 into Canada through the importation of cattle from England. From Canada the disease spread to the United States. Very few animals were infected during the 1870 outbreak, and the disease was quickly stamped out in both countries.
Europe has been unable to eradicate foot-and-mouth disease. The different outbreaks that occur from time to time cause enormous financial loss. In the United States outbreaks of the disease have occurred in the following years: 1870, 1884, 1902-'03, 1908 and 1914-'15. In the first two outbreaks very few cattle contracted the disease, and the infection was quickly stamped out. The third and fourth outbreaks were more extensive, and it was necessary to slaughter several thousand cattle and hogs in order to eradicate the disease. The first four outbreaks occurred in the eastern States, and the disease was prevented from spreading to the principal live-stock centers of the country, and the leading stock-raising States by slaughtering the diseased and exposed animals and by county and State quarantines. Early in the 1914-'15 outbreak, the disease spread to the Chicago Stock Yards, and from there, through shipments of cattle, to the principal live-stock sections of the country. The financial loss resulting from this outbreak has amounted to several million dollars. The Federal and State authorities have always been successful in stamping out the disease in the United States.
_The specific cause_ of foot-and-mouth disease is a filterable virus that is present in the serum from the vesicles, the saliva, milk, and various body secretions and excretions from the sick animal. In the early stage of the disease it is present in the blood. None of the many investigators have been able to discover the microorganism that produces the disease.
Two of the outbreaks of foot-and-mouth disease in the United States originated from an infected vaccine used for the inoculation of vaccine heifers. The origin of the 1914-'15 outbreak has not been discovered. When introduced into a country, the disease spreads rapidly, through the movement of live-stock affected by the disease. Animals recently recovered may infect other animals. Dogs, birds, people, vehicles, milk, roughage, grains and other material from an infected farm may spread the disease.
_The period of incubation is short_. Symptoms of disease may be manifested in from one to six days following exposure.
[Illustration: FIG. 106.--A cow affected with foot-and-mouth disease. Note the accumulation of saliva about the lips. (From report of the Bureau of Animal Industry.)]
_The first symptoms_ are fever, dulness, trembling and loss of appetite.
This is followed by vesicles or blisters forming on the mucous membrane of the mouth, lips, between and above the claws and the region of the udder.
The inflammation of the mouth and feet may be very painful. Long strings of saliva may dribble from the mouth and collect about the lips (Fig. 106). A smacking or "clucking" sound is produced when the animal moves its jaws and lips. The severe pain resulting from the inflammation of the mouth and feet, and the difficulty in moving about and eating and drinking, cause the animal to lose flesh and become emaciated. Milk cows may go dry.
_The death-rate is not heavy_. Some writers place it as low as two or three per cent. Because of the erosions and sloughing of the tissues of the mouth, feet and udder it becomes necessary to kill many of the animals.