The death rate in hog-cholera varies in the different forms of the disease.
The average death rate is about fifty per cent.
DIFFERENTIAL DIAGNOSIS.—The diagnosis of hog-cholera in the field must depend on the clinical symptoms, post-mortem lesions and history of the outbreak. The history should be that of a highly infectious disease.
[Illustration: FIG. 80.—Carcass of a cholera hog showing different groups of lymphatic glands; kidneys; and ulcer on caecum.]
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.
[Illustration: FIG. 81.—Kidneys from hog that died of acute hog-cholera.]
[Illustration: 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.