In neighborhoods where outbreaks of hog-cholera occur necessary precautions
against the spread of the disease are not taken. The _exchange of help_ at
threshing and shredding time in neighborhoods where there is an outbreak of
hog-cholera is the most common method of spreading the disease. _Visiting
farms_ where hogs are dying of cholera; walking or driving a team and wagon
through the cholera-infected yards; stock buyers, stock-food and
cholera-remedy venders that visit the different farms in a neighborhood may
distribute the hog-cholera virus through the infected filth that may adhere
to the shoes, horses' feet and wagon wheels. _Cholera hogs_ may carry the
disease directly to a healthy herd when allowed to run at large. _Streams_
that are polluted with the drainage from cholera-infected yards are common
sources of disease.

_Pigeons, dogs, cows_ and _buzzards_ that travel about the neighborhood and
feed in hog yards and on the carcasses of cholera hogs may distribute the
disease. Because of the active part that dogs, birds and surface drainage
take in the distribution of hog-cholera, the practice of allowing the
carcasses of dead hogs to lie on the ground and decompose is responsible
for a large percentage of the hog-cholera outbreaks.

_Age_ is an important predisposing factor. Young hogs are most susceptible
to cholera, and this susceptibility can be greatly increased by giving them
crowded, filthy quarters. Infection with lice, lung and intestinal worms,
the feeding of an improper ration and sudden changes in the ration lower
the natural resistance of a hog against disease. Pampered hogs usually
develop acute cholera when exposed to this disease.

Hog-cholera is more virulent or acute during the summer and fall months
than it is during the winter and spring months. After the disease sweeps
over a section of country, it becomes less virulent and takes on a subacute