[Ill.u.s.tration: FIG. 80.--Carca.s.s of a cholera hog showing different groups of lymphatic glands; kidneys; and ulcer on caec.u.m.]

_Abnormal body temperatures_ of a large percentage of the herd indicate the presence of an acute infectious disease. We should then destroy one of the sick hogs and make a careful post-mortem examination (Fig. 80). An early diagnosis of the disease is necessary, as this enables us to use curative treatment when it will do some good, and take the necessary steps toward preventing the spread of the disease to neighboring herds.

_Intestinal and lung worms_ are common in young hogs. The presence of these worms does not always indicate that they are the cause of the sickness and death of the animal. Such parasites are injurious and may cause disease, but it is only in rare cases that they cause death.

"_Pig typhoid_" is sometimes spoken of as a highly infectious disease involving the intestines. A disease of hogs that may be termed typhus-fever sometimes affects a large number of the hogs in the herd. This disease occurs among hogs kept in small yards and houses that are crowded, unsanitary and in continuous use, or when the hogs drink from wallows, ponds and creeks.

The term swine-plague should not be used in speaking of outbreaks of hog-cholera, as it is now considered a form of hog-cholera involving especially the lungs.

[Ill.u.s.tration: FIG. 81.--Kidneys from hog that died of acute hog-cholera.]

[Ill.u.s.tration: FIG. 82.--Lungs from hog that died of acute hog-cholera.]

LESIONS.--In _acute hog-cholera_ the inflammation is hemorrhagic in character. Small, red spots and blotches occur in different organs and tissues. In the _chronic form_ of the disease ulceration of the intestinal and gastric mucous membrane, inflammation of the lungs and pleura and sloughing of the skin are common lesions.

_The skin_ over the under side of the neck, body and inside of the thighs may appear red or purplish-red in color. The different groups of _lymphatic glands_ are enlarged and softened. They may vary in color from a grayish-red to a deep red, depending on the degree of engorgement with blood. The pleura and pericardium may show small red spots and blotches.

The _kidneys_ are usually lighter colored than normal, and marked with red spots and blotches (Fig. 81). The _spleen_ may show no evidence of disease.

It may be large and soft, or even smaller than normal. The _liver_ may be enlarged and dark, or mottled and light colored.

The _stomach_ and _intestines_ may show hemorrhagic spots and blotches.

Sometimes the gastric and intestinal mucous membrane is a brick red.

Ulceration of the mucous membrane is common (Fig. 83).

[Ill.u.s.tration: FIG. 83.--A piece of intestine from a hog that died of chronic hog-cholera, showing appearance of intestinal ulcers.]

Small, red spots may be present on the surface of the _lungs_ (Fig. 82).

Scattered lung lobules or a large portion of the lungs may be inflamed. In chronic hog-cholera, pleural exudation, adhesions and abscesses in the lung tissue may occur. Inflammations of the pericardium and heart muscle are less common lesions.

PREVENTIVE MEASURES.--Hog-cholera is the most widespread infectious disease of hogs, and all possible precautions against its distribution to healthy herds should be practised. Hogs coming from other herds and stock shows should be excluded from the home herd until they are positively shown to be free from disease. They should be quarantined in yards set off for this purpose. The hogs should be cleaned by dipping or washing them with a disinfectant. The quarantine period should be longer than the average period of incubation. Three weeks is sufficient.

_The possible introduction of the disease_ into the pens by people, dogs, birds and other carriers of the disease should be guarded against, especially if cholera is present in the neighborhood. The exchange of help at threshing and shredding time with a neighbor who has hog-cholera on his farm is a common method of distributing the infection. It is not advisable to allow a stranger to enter your hog-houses and yards, unless his shoes are first disinfected. Whenever it is necessary for a person to enter yards where the disease is present, the shoes should be cleaned and disinfected on leaving. The wheels of wagons, and the feet of horses that are driven through cholera yards, should be washed with a disinfectant. The feet of feeding cattle that are shipped from stock-yards should be treated in the same manner. Persons taking care of cholera hogs should observe the necessary precautions against the distribution of the disease, and see that others practise like precautions.

Hog-yards should be well drained and all wallow holes filled. Pens and pastures through which the drainage from the swine enclosures higher up flows should not be used for hogs.

CARE OF A DISEASED HERD.--When an outbreak of hog-cholera occurs on a farm the farm should be quarantined. The herd should be moved away from running streams, public roads and line fences, so that neighboring herds are not unnecessarily exposed to the disease. During the hot weather shade and an opportunity to range over a gra.s.s lot or pasture are highly necessary. A recently mowed meadow, or a blue gra.s.s pasture and a low shed, open on all sides and amply large for the herd to lie under, give the animals clean range and comfortable, cool quarters. Roomy, dry, well-ventilated sleeping-quarters that are free from drafts and can be cleaned and disinfected are best when the weather is cold and wet.

In the subacute, and in the early part of an acute outbreak of hog-cholera, it is advisable to separate the sick from the well hogs. The fatally sick animals should be destroyed.

[Ill.u.s.tration: FIG. 84.--Cleaning up a hog lot.]

A very light ration should be fed and an intestinal antiseptic given with the feed. A thin slop of shorts is usually preferred. Four ounces of pulverized copper sulfate may be dissolved in one gallon of hot water, and one quart of this solution may be added to every ten gallons of drinking water and slop. Water and slop should not be left in the troughs for the hogs to wallow in. The troughs should be disinfected and turned bottom side up as soon as the hogs have finished feeding and drinking. Kitchen slop and sour milk should not be fed. The care and treatment of the herd require work and close attention on the part of the attendant. Indifferent, careless treatment is of no use in this disease.

A disinfectant should be sprayed or sprinkled about the feed troughs, floors, pens and sleeping quarters daily.

DISPOSING OF DEAD HOGS.--The carca.s.ses of the dead hogs should be burned.

Before placing the carca.s.s on the fire, it should be cut open and several long incisions made through the skin. A crematory may be made by digging two cross trenches that are about one foot deep at the point where they cross, and shallow at the ends. Iron bars or pipe may be laid over the trenches where they cross for the carca.s.s to rest upon, or woven wire fencing securely fastened with stakes may be used in the place of the iron bars. If the carca.s.s is disposed of by burying, it should be buried at least four feet deep and covered with quicklime.

DISINFECTING THE YARDS AND HOUSES.--If the sick hogs are moved to new quarters at the beginning of the outbreak, the hog houses and yards should be cleaned and disinfected (Fig. 84). The manure and all other litter should be hauled away to a field where there is no danger from this infectious material becoming scattered about the premises, leaving a centre of infection in the neighborhood and causing outbreaks of cholera among neighboring herds. It may be advisable to burn the corn-cobs and other litter that have acc.u.mulated about the yards. Loose board floors should be torn up and the manure from beneath removed. Portable houses should be removed. The floors, walls of the house and fences should be first cleaned by sc.r.a.ping off the filth, and then sprayed with a three per cent water solution of a cresol or coal tar disinfectant to which sufficient lime has been added to make a thin whitewash. Three or four months of warm, sunny weather are sufficient to destroy the cholera infection in well-cleaned yards.

ANTI-HOG-CHOLERA SERUM.--The credit of developing the first and at present the only reliable anti-hog-cholera serum and method of vaccination belongs to Drs. Dorset and Niles. Anti-hog-cholera serum came into general use in 1908, and all of the swine-producing States have established State laboratories for the production of this serum.

Anti-hog-cholera serum is produced by injecting directly, or indirectly, into the blood-vessels of an immune hog a large quant.i.ty of cholera virus, secured by bleeding a hog that is fatally sick with acute cholera, and bleeding the injected animal after it has completely recovered from the injection. The injection of the cholera blood is for the purpose of stimulating the production of antibodies by the body tissues, and raising the protective properties of the immune hog's blood. An animal so treated is called a hyperimmune (Fig. 85). The blood from the hyperimmunes is defibrinated and a preservative added, and after it has been tested for potency and freedom from contaminating organisms, it is ready for use.

[Ill.u.s.tration: FIG. 85.--Hyperimmune hogs used for the production of anti-hog-cholera serum.]

THE VACCINATION OF HOGS WITH ANTI-HOG-CHOLERA SERUM.--The vaccination of a hog by the single method consists in injecting hypodermically or intramuscularly anti-hog-cholera serum. The immunity conferred may not last longer than three or four weeks.

The vaccination of a hog by the _double method_ consists in injecting hypodermically or intramuscularly anti-hog-cholera serum and hog-cholera blood.

_The vaccination or treatment_ of a cholera hog showing noticeable symptoms, or a high body temperature, consists in injecting hypodermically or intramuscularly anti-hog-cholera serum (Fig. 87).

[Ill.u.s.tration: FIG. 86.--Preparing the hog for vaccination by washing the part where the serum is injected with a disinfectant.]

[Ill.u.s.tration: FIG. 87.--Vaccinating a hog.]

_The region_ into which the serum and cholera blood may be injected are the inside of the thigh, within the arm, flank and side of the neck (Fig. 86).

Two hypodermic syringes, holding about twenty cubic centimetres and six cubic centimetres, and having short, heavy, seventeen or eighteen-gauge slip-on needles, should be used. The small syringe is used for injecting the virulent or cholera blood which is injected into a different part than the serum. The quant.i.ty of serum and virus injected varies with the size and condition of the animal. _Young hogs_ should receive one-half cubic centimetre of serum for each pound of body weight, and _cholera hogs_ should be given one-half more to twice the dose that is recommended for healthy animals. The dose of virus recommended varies from one to two cubic centimetres for each hog.

In vaccinating _small pigs_ not more than five, and in large hogs not more than twenty, cubic centimetres should be injected at any one point. The _body temperature_ of each animal should be taken. A body temperature of 103.5260 F. in a mature hog and a body temperature of 104260 F. in a young hog may indicate hog-cholera. Exercise, feeding and close confinement in a warm place may raise the body temperature above the normal.

Hogs that are to be vaccinated or treated should not be given feed for at least twelve hours before handling them. If possible they should be confined in a roomy, clean, well-bedded pen. If this is practised, they are cleaner and easier to handle and their body temperatures are less apt to vary. After the treatment or vaccination the hogs should be fed a light diet for a period of at least ten days, and the ration increased gradually in order to avoid causing acute indigestion. This is necessary because of the elevation in body temperature resulting from the inability of the animal to digest heavy feeds, kitchen slops and sour milk. If poor judgment is used in caring for the vaccinated hogs, and the person who vaccinates them uses careless methods, heavy losses from acute indigestion, blood poisoning, or hog-cholera may occur.

QUESTIONS

1. What is the specific cause of hog-cholera? Give and describe the different methods of spreading the disease.

2. What are the symptoms of hog-cholera?

3. Give the preventive and curative treatment of hog-cholera.

4. What is anti-hog-cholera serum? Give the different methods of vaccination and treatment.

CHAPTER XXVII

TUBERCULOSIS

[Ill.u.s.tration: FIG. 88.--Koch's _Bacillus tuberculosis._]

Tuberculosis is a contagious an and domestic animals, affecting any the lymphatic glands and lungs, change in the tissues is the formation tubercle or nodule.

HISTORY.--Tuberculosis is one of the oldest of known diseases of domestic animals and man. Its contagious character was proven by Villemin in 1865, who by experential infection transmitted tuberculosis from man to animals and from animal to animal. It was in 1882 that Dr. Robert Koch discovered and proved by inoculation experiments that the disease was caused by a specific germ (Fig. 88). Prior to the experiments by Villemin and Koch, the belief was that tuberculosis was due to heredity, unsanitary conditions and inbreeding. Following discovery of the specific germ and conditions favoring its development and spread, numerous scientifically conducted experiments were made. These resulted in practical methods of control and elimination of tuberculosis from herds having this disease. By carefully conducted experiments and other forms of educational work the infectious character of tuberculosis and the economic importance of preventative measures have been demonstrated. The average stockman is well informed regarding the character and economic importance of this disease, but there is no general application of this knowledge, and tuberculosis is increasing in dairy and breeding herds. The slow development of tuberculosis, and the absence of visible symptoms during the early stage of the disease, are responsible for this condition and the extensive infection of dairy and breeding herds.

PREVALENCE OF THE DISEASE.--Tuberculosis is very prevalent among cattle and swine in all countries where intensive agriculture is practised. It is a rare disease among cattle of the steppes of eastern Europe and the cattle ranges of the western portion of the United States. In countries where dairying is an important industry, tuberculosis is a common disease of cattle and hogs. The abattoir reports of Europe and the United States show that tuberculosis is on the increase among domestic animals. The Bureau of Animal Industry of the United States Department of Agriculture reports that out of 400,008 cattle tested with tuberculin 9.25 per cent reacted. Melvin states that the annual loss from tuberculosis in the United States is about $23,000,000. In dairy herds in which the disease has existed for several years, it is not uncommon to find from 25 to 75 per cent tubercular.