History. Cause: bacillus. Symptoms; incubation 6 to 15 days, skin
tenderness, heat, swelling like peas, hazel nuts, vesicles, pustules,
exudation, concretions among hairs, depilation, healing in 15 days.
Leaves white spots with lighter hair. Extension by grooming: general
eruption: subcutaneous swelling, sloughs, delayed healing.
Lymphangitis. Diagnosis: from chaps and bruises, from horse pox, from
impetiginous eczema, from urticaria, from farcy. Prevention,
quarantine new horses, separate diseased, disinfect skins of the
unaffected, disinfect stables and harness. Treatment: soapy wash:
germicide lotions.
This has been largely described as an imported disease thus on the
European continent it is the English variola, and in England the
Canadian contagious pustular affection. Yet the first authentic account
dates back to 1841–2 when Goux found it attacking an entire squadron of
the French army in a fortnight. Axe described it in England in imported
Canadian horses in 1877, and Weber observed it in the same year on the
continent, where it was attributed to imported English horses. In 1883
it was noted by Schindelka, in 1884 Siedamgrotzky inoculated it from the
horse on two rabbits and two Guinea pigs, and to horse and goat. The
rodents developed a “malignant œdema” at the point of inoculation and
died in six days. Grawitz and Dieckerhoff cultivated the bacillus on ox
or horse serum and found it 2μ in length, dividing by segmentation into
round or ovoid refractive spores, which may remain connected as
diplococci or short chains and which color deeply in fuchsin. It grows
most rapidly at a temperature of 37° C., growth ceases at 17° C., and it
is destroyed in half an hour at 80° to 90° C. Preserved, dry, it
remained virulent for four weeks and produced the characteristic
eruption when rubbed on the skin of the horse, ox, dog, sheep or rabbit.
It proved fatal to all rodents, including white mice. The microbe is
found abundantly in the pus and crusts and is easily shown when these
are treated with potash. It produces no putrid fermentation.
_Symptoms._ When inoculated it had an incubation of six to fifteen days
followed in mild cases by swelling heat and tenderness of the skin with
collection of the hair in erect tufts. Next day there are rounded
elevations like peas or hazel nuts, discrete or confluent on the swollen
patches. These nodules, at first firm and resistant soon become soft in
the center, forming vesicles and finally pustules, which burst in five
or six hours and exude an abundant liquid which concretes in a thick
amber colored mass. The hairs in the center of the resulting raw surface
are easily detached leaving bare spots the size of a dime, with often
times a slough attached in the center. When this is finally eliminated
the surface gradually cicatrices and recovery may be complete in fifteen
days. The skin remains long dappled from the partial discoloration of
the epidermis in the seat of the pustules. The malady is local and
hyperthermia is rarely seen. The submaxillary and pharyngeal lymph
glands are usually swollen and indurated, but this disappears speedily
after the subsidence of the eruption.
In certain cases the extent of the primary eruption is greater from the
first, or it extends through reinfection by combs, brushes and rubbers
used in grooming or by friction by the harness, the affected skin is
hot, painful, congested and thickened throughout its entire substance,
the pustules are much more numerous, often confluent, and may even
implicate the subcutaneous connective tissue. The crusts formed on the
sores may acquire a breadth of 1 inch to 1½ inch. Considerable abscesses
may be formed and the lymph glands communicating with the affected part
are hot and swollen. Even after the opening and discharge of the
abscess, the base of the sore remains indurated and indolent, and
centres of softening and caseation may appear so that healing is delayed
for one or two months or more. In such cases extensive cicatrices remain
after recovery. Lymphangitis is a common accompaniment with even abscess
of the lymphatic glands.
_Diagnosis._ From chafing and bruising by the harness, this is easily
recognized by its appearing also on other parts than those covered by
the harness, by the development of the characteristic pustules, by its
following a regular cycle of eruption and subsidence covering a definite
period of usually 15 days, and by the indisposition to maintain itself
indefinitely under the friction of the harness.
From _horsepox_ it is distinguished by the habitual avoidance of the
common seats of election of that disease (heels, lips, nostrils, buccal
and nasal mucosæ, lips of the vulva), by the absence of hyperthermia,
and by the comparative absence of the remarkable amber-like concretions
which characterize horsepox in the lower limb.
From _impetiginous eczema_ it is diagnosed by its contagious and
inoculable properties, by the absence of the early falling of the hair
from the circumscribed rounded nodules, and by the absence or moderate
character of the pruritus which is usually intense in the eczema.
The eruption of _urticaria_ appears much more suddenly, shows no
tendency to form vesicles nor pustules, is not inoculable, and subsides
often as suddenly as it appeared when the irritant food materials have
been expelled from the alimentary canal.
From acute _farcy_ it is distinguished by the moderate degree of the
implication of the lymph vessels and glands, by the white creamy nature
of the contents of the pustules, as compared with the glairy, oily
nature of the farcy discharge, by the absence of coincident nasal
ulcers, submaxillary nodular swellings or other lesions of glanders, by
its short course and tendency to spontaneous early recovery, and by the
absence of reaction under the mallein test.
In all cases the known prevalence of the contagious pustular dermatitis
in the locality, or the introduction of strange horses which exhibit
sequelæ of the lesions will assist greatly in the diagnosis.
_Prevention._ If animals are introduced from an infected or unknown
locality they should be kept apart from others for two weeks. In a
stable where it has already appeared the diseased and healthy should be
carefully separated and the skins of those as yet unaffected may be
washed with a solution of mercuric chloride (1 ∶ 1000) or creolin (1 ∶
100). The walls of the stable should be whitewashed, and all stable
utensils disinfected in boiling water or one of the above named
antiseptics. The harness demands particular attention.
_Treatment._ This is essentially germicide. After a soapy wash, any one
of the usual disinfectants may be used: aluminum acetate, (1 ∶ 15),
mercuric chloride (1 ∶ 1000), carbolic acid (1 ∶ 50), creolin (1 ∶ 50),
copper sulphate (1 ∶ 50), etc. Lead acetate 2 parts, alum 1 part and
water 50 parts, has been found to be effective.