rinderpest virus appeared spontaneously under the influence of deteriorated
feed and long and exhausting drives; also during unusual meteorological
conditions. This view, however, is no longer maintained. It is probable
that in its home in Asia the disease is perpetuated by continual infection
of fresh animals, and some authorities go even so far as to believe that
the disease would be entirely stamped out, even in its native haunts, by a
destruction of all sick and infected herds. However this may be, the
success of such an undertaking would largely depend on the nature of the
cause. If a strictly parasitic organism, like the contagion of
pleuropneumonia, it might be completely extirpated in this way. If,
however, the germs or bacteria may live and multiply outside of the bovine
body, in the soil, water, or in some other animal, extirpation would be
impossible.

The virus may be transmitted in a variety of ways, both direct and
indirect, from sick to healthy animals. It is said to be present in the
various excreta, such as the discharges from the nose, and the saliva, the
urine, and the manure, of the diseased. For months it retains its vitality
in a moist state outside the body, and the disease is reported to have
developed after feeding hay a year after it had lain in an infected stable;
hence manure and the fodder and bedding soiled with discharges may convey
it. Persons may carry the virus on their shoes, clothing, or implements.
Even small animals, such as cats and rats, which frequent barns and
stables, have been looked upon as carriers of the virus.

Cattle are very susceptible to the disease, and in its virulent type all
those exposed are said to become infected. Buffaloes, sheep, and goats are
likewise susceptible, but in a less degree.

It is also claimed that animals after having passed through one attack
successfully resist future attacks. Inoculation with virus is said to
produce immunity, but in many cases the process of inoculation itself is
followed by death.

_Symptoms._--The symptoms of rinderpest are not very characteristic, and
hence the diagnosis of a suspected case in the beginning of an invasion is
attended with difficulties. Certain appearances which are characteristic of
one epizootic may be absent in another. Different observers are not quite
agreed as to the most constant and important.

The period of incubation, i. e., the time between the exposure to infection
and the earliest outward