or chronic form. Outbreaks of hog-cholera usually last two or three years
in a neighborhood. This depends largely on the number of susceptible hogs
that were not exposed to the infection the first season, and the preventive
precautions observed by the owners.

PERIOD OF INCUBATION.--The length of time elapsing between the exposure of
the hog to the cholera virus, and the development of noticeable symptoms of
hog-cholera, varies from a few days to two or three weeks. The length of
this incubation period depends on the susceptibility of the animal, the
virulence of the virus and the method of exposure. An acute form of
hog-cholera indicates a short period of incubation, and a chronic form, a
long period.

SYMPTOMS.--The symptoms of hog-cholera may differ widely in the different
outbreaks of the disease. The symptoms may be classified under the
following forms: Acute, subacute and chronic. The acute form of hog-cholera
is the most common. The early symptoms are tremors, fever, depressed
appearance, marked weakness, staggering gait, constipation and diarrhoea,
labored breathing and convulsions. Death may occur within a few hours or a
few days. Recovery seldom occurs. In the subacute form, the symptoms are
mild and develop slowly. Recovery may take place within a few days, or
after extending over a week or ten days it may assume the chronic form.
Very often in outbreaks of subacute cholera a large majority of the herd
does not show visible symptoms of the disease. In the chronic form, marked
symptoms of pleuropneumonia and chronic inflammation of the intestine are
common. Ulcers and sores form on the skin and the hair may come off. Large
portions of the skin may become gangrenous and slough. Young hogs are
usually stunted and emaciated.

_The first symptom_ of disease is an elevation of body temperature.