One name for several affections. Differentiation, swine erysipelas,
hog cholera and swine plague. Complex infections. Effects of large,
medium and small doses, of more or less potent germ, of greater or
less susceptibility.
Until comparatively recent years the various infectious fevers of swine
have been confounded and described as a single disease, the name varying
in the different countries in which they were observed. In America it
was _Hog Cholera_; in England, _Swine Fever_; in France, _Rouget_; and
in Germany, _Schweineseuche_. A closer study showed a marked tendency to
a particular class of lesions in different epizoötics, and
bacteriological research associated plagues in given localities with
different microbes, so that progress has been made in differentiating
one from another to a certain extent.
The first clear distinction was made in setting aside the swine
erysipelas (rouget, rothlauf,) from the rest as distinguished at once by
its small, delicate bacillus, differing notably from the others in its
staining and cultural peculiarities, as well as in the predominance of
the cutaneous lesions.
What remains after eliminating erysipelas, constitutes a group having so
much in common that attempts at further differentiation have led to much
disputation, and not even to-day is there such accord in different
countries as the writer of a text-book would find desirable. One class
of pathologists claims but one common disease with many varieties under
different conditions, just as the term _septicæmia_ or _blood poisoning_
has been made to designate a whole class of local and general
infections, irrespective of the particular microbes that cause them.
Others with greater precision give the disease a name according to the
causation by one particular microörganism, or by another, which may be
closely related to it in many respects, but which in successive subjects
and outbreaks, maintains its own individual characteristics as regards
morphology, cultural and staining habits, pathogenesis, etc. The
question has been rendered all the more trying, by the occasional
association in the same animal system, or in the same outbreak of two
distinct varieties of microörganisms, in place of one, giving rise of
course to modifications in the symptoms, lesions, progress, mortality,
etc.
Apart from the microörganism the whole class tends to show a close
family relationship in their pathological phenomena shown under
different conditions :
1st. Under a large dose, or specially virulent germ, in a particularly
susceptible animal, all tend to a manifestation of an acute septicæmia,
with generally diffused petechiæ of the skin, mucosæ, serosæ and
internal organs, blood extravasations, and an early high mortality.
2d. Under a smaller dose, or a less potent germ, or in a less
susceptible animal the tendency is to necrotic processes in the seat of
inoculation or the point of election of local lesions. Necrotic ulcers
are especially common in cases that survive one, two or three weeks, or
that develop in a subacute or chronic form.
3d. With a minimum dose of a germ of little potency, and in a very
resistant subject even the necrotic lesions may be absent, and there may
be suppuration only or ulceration of serosæ and joints.
The question of the primary identity, or disparity of the whole class of
germs, causing the septicæmic swine plagues, may be practically ignored
in this work; it is important rather with our present knowledge to note
the diseases associated with particular germs, or varieties of germs,
and to describe these as far as possible as independent affections. This
is as permissible as it is to describe smallpox, sheeppox, and cowpox as
distinct affections, no matter what may be the truth or falsity as to
their alleged original identity.
_Rouget_ in Europe and _Hog Cholera_ and _Swine Plague_, as the best
established types in the United States deserve primary mention, to be
followed by references to additional types which have been found to be
associated with other distinct microörganisms.