This is a cutaneous disease, analogous to the mange in horses and the
itch in man, and is caused and propagated by a minute insect, the
_acarus_.
[Illustration: THE BROAD-TAILED SHEEP.]
If one or more female _acari_ are placed on the wool of a sound sheep,
they quickly travel to the root of it, and bury themselves in the skin,
the place at which they penetrate being scarcely visible, or only
distinguishable by a minute red point. On the tenth or twelfth day, a
little swelling may be detected with the finger, and the skin changes
its color, and has a greenish blue tint. The pustule is now rapidly
formed, and about the sixteenth day breaks, when the mothers again
appear, with their little ones attached to their feet, and covered by a
portion of the shell of the egg from which they have just escaped. These
little ones immediately set to work, penetrate the neighboring skin,
bury themselves beneath it, find their proper nourishment, and grow and
propagate, until the poor creature has myriads of them preying upon him.
It is not wonderful that, under such circumstances, he should speedily
sink. The male _acari_, when placed on the sound skin of a sheep, will
likewise burrow their way and disappear for a while, the pustule rising
in due time; but the itching and the scab soon disappear without the
employment of any remedy. The female brings forth from eight to fifteen
young at a time.
In the United States, this disease is comparatively little known, and
never originates spontaneously. The fact, that short-woolled sheep--like
the Merino--are much less subject to its attacks, is probably one reason
for this slight comparative prevalence. The disease spreads from
individual to individual, and from flock to flock, not only by means of
direct contact, but by the _acari_ left on posts, stones, and other
substances against which diseased sheep have rubbed themselves. Healthy
sheep are, therefore, liable to contract the malady, if turned on
pastures previously occupied by scabby sheep, although some considerable
time may have elapsed since the departure of the latter.
The sheep laboring under the scab is exceedingly restless. It rubs
itself with violence against trees, stones, fences, etc.; scratches
itself with its feet, bites its sores, and tears off its wool with its
teeth; as the pustules are broken, their matter escapes, and forms
scabs, causing red, inflamed sores, which constantly extend, increasing
the misery of the tortured animal; if unrelieved, he pines away, and
soon perishes.
The _post-mortem_ appearances are very uncertain and inconclusive. There
is generally chronic inflammation of the intestines, with the presence
of a great number of worms. The liver is occasionally schirrous, and the
spleen enlarged; and there are frequently serous effusions in the belly,
and sometimes in the chest. There has been evident sympathy between the
digestive and the cutaneous systems.
_Treatment._ First, separate the sheep; then cut off the wool as far as
the skin feels hard to the finger; the scab is then washed with
soap-suds, and rubbed hard With a shoe-brush, so that it may be cleansed
and broken. For this use take a decoction of tobacco, to which add
one-third, by measure, of the lye of wood-ashes, as much hog's lard as
will be dissolved by the lye, a small quantity of tar from a tar-bucket,
which contains grease, and about one-eighth of the whole, by measure, of
spirits of turpentine. This liquor is rubbed upon the part infected, and
spread to a little distance around it, in three washings, with an
interval of three days each. This will invariably effect a cure, when
the disorder is only partial.
Or, the following: Dip the sheep in an infusion of arsenic, in the
proportion of half a pound of arsenic to twelve gallons of water. The
sheep should be previously washed in soap and water. The infusion must
not be permitted to enter the mouth or nostrils.
Or, take common mercurial ointment; for bad cases, rub it down with
three times its weight of lard--for ordinary cases, five times its
weight. Rub a little of this ointment into the head of the sheep. Part
the wool so as to expose the skin in a line from the head to the tail,
and then apply a little of the ointment with the finger the whole way.
Make a similar furrow and application on each side, four inches from the
first; and so on, over the whole body. The quantity of ointment after
composition with the lard, should not exceed two ounces; and, generally,
less will suffice. A lamb requires but one-third as much as a grown
sheep. This will generally cure; but, if the animal should continue to
rub itself, a lighter application of the same should be made in ten
days.
Or, take two pounds of lard or palm oil; half a pound of oil of tar; and
one pound of sulphur; gradually mix the last two, then rub down the
compound with the first. Apply as before. Or, take of corrosive
sublimate, one half a pound; white hellabore, powdered, three-fourths of
a pound; whale or other oil, six gallons; rosin, two pounds; and tallow,
two pounds. The first two to be mixed with a little of the oil, and the
rest being melted together, the whole to be gradually mixed. This is a
powerful preparation, and must not be applied too freely.
An erysipelatous scab, or erysipelas, attended with considerable
itching, sometimes troubles sheep. This is a febrile disease, and is
treated with a cooling purgative, bleeding, and oil or lard applied to
the sores.