Definition, Synonyms, History, Losses. Bacillus choleræ suis, 1.2–2μ.,
ærobic, biology, table of germs; accessory causes, roaming pigs,
railways, car litter and manure, boats, trucks, loading banks, chutes,
runways, stockyards, pens, fairs, watershed, butchers, dealers, etc.,
wagons, dogs, birds, vermin, insects, offal of abattoirs, butcher’s
and kitchen scraps, unburied carcasses of dead hogs, convalescent and
immune hogs, susceptibility, parasites and infection atria, putrid
food, infection from ground carried into feeding trough by snout and
feet, large herds, rapid carriage of swine for long distances.
Lesions: hæmorrhagic spots and petechiæ on skin, mucosæ and serosæ,
circumscribed capillary congestions, congestion of spleen, lymph
glands, stomach, intestines, necrotic processes. Button-like ulcers on
intestinal mucosæ. Incubation, 6 to 14 days. Symptoms: fulminant
cases. Acute Cases: dulness, anorexia, recumbency on belly, weakness,
paresis behind, thirst, tenderness of skin and abdomen, hyperthermia,
easily blown, blush on skin, dark red spots and patches, enlarged
inguinal glands, cutaneous exudate—greasy or drying black, bowels
costive, later pultaceous and finally diarrhœaic, petechiæ on mucosæ,
emaciation. Chronic Cases: symptoms more slight, but great loss of
condition. Diagnosis: from swine erysipelas, swine plague, Widal test,
table of differential symptoms. Prevention: expense of extinction
prevents effective measures; removal of accessory causes, comfort,
air, light, food, salt, powdered soaps, mouldy bread, cotton seed,
space, green food, precautions against introduction of bacillus,
special shipping provisions for fat hogs, exclusion of stock hogs from
infected localities, precautions by purchasers. Immunization,
Disinfection. Certificates. Extinction in herds and districts.
Treatment: chronic cases, food, antiseptic medication, antithermics
stimulants, tonics. Serum therapy, method, merits, demerits.
_Definition._ A contagious bacteridian disease of swine, acute or
subacute, and characterized by hyperthermia and other febrile
disorders,—congestion, exudation, ecchymosis and necrotic ulceration of
the intestinal mucosa and of that of the stomach and of other parts,—by
a profuse foul, liquid diarrhœa, by enlargement of the lymph glands with
congestion and blood extravasation,—by effaceable blotches, and petechiæ
(ineffaceable) of the skin, snout and visible mucosæ, with a tendency to
necrotic changes—less frequently by pulmonary congestions, and
degeneration,—and by a high mortality.
_Synonyms._ The earlier designations were mostly drawn from the red or
black discoloration of the skin and mucosæ and applied indiscriminately
to the other forms of hæmorrhagic septicæmia which we now differentiate
as erysipelas (rouget, Rothlauf) and swine plague. They included
_measles_, _erysipelas_, _scarlatina_, _red soldier_, _purples_, _blue
sickness_, _carbuncular fever_, etc. Others basing their nomenclature on
the prominent intestinal lesions, etc., designated it _typhoid fever_,
_pig typhoid_, _typhus_, _carbuncular gastro-enteritis_,
_pneumo-enteritis_, and _diphtheria_. Even in Europe while the _pig
erysipelas_ (_rouget_, _Rothlauf_) is now recognized as a distinct
disease there is no clear distinction made between _hog cholera_ and
_swine plague_. In England we find these more or less confounded under
the names of _swine fever_, _swine plague_ and _hog cholera_, and on the
continent of Europe under those of _schweineseuche_ and _schweinepest_,
or _pneumo-enteritis infectieuses_. Differences in different epizoötics
or outbreaks are recognized, and the field is left open for the future
identification of different forms of this common group of swine fevers,
but the existence of constant bacteriological distinctions are not
always insisted on, as we do in the United States in the case of the two
great leading types _swine plague_ and _hog cholera_.
_History._ Definite history of this disease may be said to begin with
the discovery and demonstration of the actively motile hog cholera
bacillus by the U. S. Bureau of Animal Industry in 1885. Yet in the
history of animal plagues, even in early times, deadly epizoötics are
described which undoubtedly represented one or other of the contagious
affections of modern times. Among the more definite may be named a
destructive gastro-enteritis (magen seuche) in Germany in 1817, a
pleuro-pneumonia in France and Bavaria in 1821, a cholera with blotching
of the skin (morbus niger) in Ireland, and an erysipelas in pigs in
France and Switzerland in 1836, and in Ohio in 1833, there was a fatal
affection afterward recognized as hog cholera. Writers conjecture that
it was imported into America from Europe in improved pigs, and from one
European country to another in the same way, but we have no absolute
proof of times and shipments and their immediate effects, so that these
theories are but more or less reasonable deductions from the familiar
extensions of the disease in more recent cases. Under the great
commercial activity of the latter half of the 19th century, the active
movements of animals by canal, steamboat and rail, and the massing
together in one market of many animals drawn from widely different
sources, hog cholera has made extraordinary extensions on both sides of
the Atlantic, until Friedberger and Fröhner pronounce the schweineseuche
and schweinepest the most widely disseminated and dangerous of swine
epizoötics, and Dr. Salmon estimates the losses in the United States at
$10,000,000 to $25,000,000, per annum.
_Bacteriology._ Prior to 1885 bacteria had been found in the different
outbreaks of contagious fevers in swine, and the bacillus of swine
erysipelas had been demonstrated in 1882, but it was only two years
later (1884) that the motile bacillus choleræ suis was first described
by Klein, and in 1885 that Salmon and Smith demonstrated it as the
essential cause of the disease, together with its biological and
cultural peculiarities.
It is a short bacillus, 1.2 to 2μ × 0.5 to 0.8μ, but varying
considerably in size according to the stage of its growth and the genera
of animal or culture medium in which it is grown. It has rounded ends
and is usually in pairs connected by an invisible band. It stains
promptly in all the aqueous aniline colors, but loses the stain in a
solution of iodine (Gram’s). Prolonged exposure of artificial cultures
produces an uniform stain, while a transient exposure, and especially of
bacilli obtained from the tissues, stains them most deeply at the ends
(polar) and periphery, while the centre remains somewhat clear. This is
less marked than in the bacillus of swine plague, yet serves to show the
relation between this microbe and the colon group.
It is _ærobic_ (facultative anærobic), non-liquefying, and, in fluids,
very actively motile, the movements lasting for months in preserved
specimens (Smith). It grows luxuriantly in various culture media, and
especially in alkaline ones, at the room temperature, and most actively
at 85° to 100° F. It may grow as low as 60° to 70° F. and as high as
104°. (Swine plague bacillus grows at 55.4°).
On _peptonized gelatine_ the surface colonies are usually round and
flattened, those in its substance globular and smaller, and those at the
bottom expanded next the glass and rising in the center into the
gelatine like a knob. At 48 hours they appear as opaque whitish points
and slowly increase to ½ to 2 mm. They may be brown by transmitted
light, the depth of color increasing with age. On _agar_ the colonies
are grayish, shining and translucent and may reach the size of 4 to 6
mm. On _potato_ (alkaline) a straw yellow film is formed, darkening with
growth. In _bouillon_ a turbidity appears in 24 hours, and in 1 or 2
weeks a precipitate and surface film.
The bacillus is usually larger in the gelatine and smaller in the
bouillon than it is in the tissues. It seems to produce neither phenol
nor indol.
Its behavior with sugars is significant. It ferments glucose producing
acid and gas; does not ferment saccharose nor lactose, but turns the
saccharose solution alkaline (no gas). In bouillon containing muscle
glucose, it may without additional glucose form a little gas. The swine
plague bacillus ferments saccharose producing acids but no gas: it
ferments neither glucose nor lactose but turns the former acid.
Milk is neither coagulated nor soured by the hog cholera bacillus, but
in 3 to 4 weeks it undergoes a change, becoming saponified.
Cultures have no special nor offensive odor. Some varieties in close
tubes may cause a faint acid odor.
Oxygen is not essential to the success of a culture. The colonies form
as promptly and as large in the depths of gelatine, or in a vacuum, as
if in free air.
The following table will serve to show differences between the hog
cholera bacilli, and related pathogenic microbes:
=Hog Cholera.= =McFadyean’s.= =Swine Plague.=