Giltner and others have proven that the Bang bacillus of abortion is
infectious for other species of animals, and outbreaks of this disease have
been said to occur among breeding ewes pastured and fed on infected
premises. Its infectiousness for the females of other species has never
been proven in natural outbreaks.

The disease-producing germs are present in the body of the foetus, the
fetal membranes, the discharge from the maternal passages, the faeces and
milk of aborting animals. The male may carry the infection in the sheath,
urethra and on the penis. The natural avenues of infection are the maternal
passages and digestive tract.

It is very seldom that abortion is carried from one herd to another by
means other than through the breeding of animals free from abortion to
animals affected by this disease. The purchase of a bull or cow from an
infected herd and breeding them to animals that are free from disease, is a
common method of spreading the disease. After serving the diseased animal,
the male may carry the bacillus of abortion into the maternal passages of
the next cow he serves. There are numerous cases on record where the bull
was a permanent carrier of the Bacillus abortus and infected nearly every
animal served. The distribution of the disease in the herd following the
introduction of a cow, sow, or ewe that has aborted before or after being
purchased, takes place through contact of the other animals with the virus
that may be present on the floor, or in the manure, or by taking the virus
into the digestive tract along with the feed and drinking water.
Experimental evidence indicates the latter avenue of infection.

The stallion is the most common source of infectious abortion in mares. An
infected stallion may distribute the disease to a large percentage of the
mares that he serves. For this reason nearly all of the mares in a certain