62
(h.)—Proportion of animals liable to be attached on exposure to the ' materies
morbi' of ' Surra'.—We have no statistics bearing on the question, with the
exception of those published by Rimington. He states, that out of a total stud of
739 horses in 1889, forty-seven were attacked and succumbed, or were destroyed
on account of Surra.
(i.)—Immunity from subsequent attacks.—Death follows the first attack in all
the above mentioned animals, with the exception of bovine species, and our experi-
ments tend to prove that one attack may grant immunity to these animals, at all
events for a considerable period.
SECTION VII.
SYMPTOMS OF SURRA.
Clinical Description.
Before describing the symptoms of Surra, it will be neccessary first to divide
cases of the disease under two different heads, viz.:—
A.—Those which have contracted the disease in the natural course of
events.
B.—Those which have acquired the disease by inoculation.
A.—Symptoms of the disease as observed when contracted naturally.—The
invasion of this disease is usually marked by symptoms of a trivial character,
the skin feels hot, and there may be more or less fever ; there is also slight loss
of appetite, and the animal appears dull and stumbles during action ; thus early
a symptom sometimes appears, which may be the first intimation received of
the animal's indisposition, and which as a guide to diagnosis is of great importance ;
it is the presence of a general or localized urticarial eruption. If the blood be
examined microscopically it may be found to present a normal appearance, but
in the majority of cases a few small rapidly moving organisms will be observed,
giving to the blood, as it passes amongst the corpuscles a peculiar vibrating move-
ment, which if once observed will not readily be forgotten. If the hæmatozoon
has not been discovered in the blood for some days, the before-mentioned may
be the only symptoms noticeable, and as a rule when treated with febrifuges,
the horse quickly improves in health and the appetite returns. This condition
does not last for more than a few days, when the animal is again observed to
present a dull and dejected appearance, and on examination well marked
symptoms are found ; the skin is hot, the temperature more or less elevated,
38.7°C. to 40°C., the pulse full and frequent, 56 to 64 beats per minute, the
visible mucous membranes may appear clean, but the conjunctival membranes,
especially those covering the membrana nictatans, are usually the seat of dark
red patches of ecchymosis, varying in size in different animals. There is more or
less thirst, and slight loss of appetite, the animal eating its corn and green
grass, whilst leaving all or a portion of the dried grass with which it has been
supplied. At the same time there are slight catarrhal symptoms present, includ-
ing lachrymation, and a little mucous discharge from the nostrils. Occasionally
at this period of the disease the submaxillary glands may be found enlarged, and
perhaps somewhat tender on manipulation. One symptom is markedly absent,
namely, the presence of rigors, or the objective signs of chilliness. In addition it
will be noted, that there is some swelling and oedema of the extremities, generally
between the fetlock and the hock, which pits, but is not painful on pressure, and
in the case of horses there may be present also at this stage of the disease, some
swelling of the sheath. When the fever and concomitant symptoms have declared
themselves during a short period, one thing becomes especially noticeable in every
animal attacked, namely, the rapidity with which it loses flesh. If the blood
has been examined microscopically during the second period of fever, at first
a few hæmatozoa will have been observed in it, which day by day increase
in number and reach a maximum, where they remain for a varying period,
or at once suddenly or gradually disappear during the period of apyrexia.
After the fever and the accompanying symptoms have for the second time
been present for some days, the period varying from one to six, the animal
is found to have lost the dull dejected appearance, and to look bright ; the