The record-union., 1898-11-15
SKETCH oF SHEEP sCAB.
Contagious Skin Disease Caused by
Parasitic Mite.

| The disease commonly called sheep
scab is the mango, or scabies, of the
| sheep. 1t is a contagious skin disease
caused by parasitic mite. This dis
| ease is one of the oldest known, most
prevalent, and most injurious maladies
which affects this species of animals 1t
has been we'll known for many centu-
ries, and references to it are found in
the earlier writings, including the BIZ
bic, where we find in Leviticus xii %
the use of scabbed sheep forbidden in
sacrifices. Some think that the mite
which causes the disease was known to
Aristotle, 322 B. c.; but it appears that
Wichmann writing in 1856, was one
of the first authors of modern times to
suspect that sheep scab was of the
same nature as the scabies of man.
Wichmann held the erroneous view,
however that both diseases were pro-
duced by the same parasite.
The prevailing opinion concerning
scab prior to and during the first years
of the present century was that it was
caused by some special condition of the
Sleeps system, a "humor of the blood"
which led to a skin eruption. The par
aSiteS were in some cases known and
recognized, but they were supposed to
be either an accidental occurrence or
to have arisen by spontaneous genera
ton as a result of the disease, and be-
cause the affected skin offered condi-
tions favorable to their development
and existence.
AS result of diligent research GER
tain investigators reached the conclu-
sion that the rnalady was due directly
to the mites which were found inhab-
iting the diseased parts of the skin
Their opinion was not at once adopted,
however, but, on the contrary, met with
strong opposition from those who held
that scab was due to a diseased condi-
tion of the blood and from others who
held a modified view to the effect that
the mites carried poisonous or diseased
material from one animal to another
and in that manner communicated the
disease. The errors and uncertainties
which came down to us through CEN
turies of controversy We're finally and
for all time dispelled by conclusive ex-
periments upon animals made during
the first half of this century. 1t was
shown that seab does not develop ana
cannot be produced without the para
sites. The complete life cycle of the
mites was studied and demonstrated
from the eggs to the adult parasites. IL
was shown that mites are always the
offspring of ancestors, the same as are
the larger animals, and it has in later
years come to be admitted that there
is no such thing known as spontaneous
generation of any living thing under
any circumstances. The demonstration
was repeatedly made that the disease
always developed If mites were taken
from diseased sheep and placed upon
healthy ones, and that diseases of the
skin resembling scab are not contagious
unless the mite is present.
Questions are still frequently asked,
by persons not conversant with the in
vestigations of the subject, as to wheth-
er the seab is the cause of the mite or
the mite is the cause of the scab, and
also whether the disease can develop
without the presence of the scab mite.
The Investigations which have been re-
ferred to answer these questions and
also show that the treatment must con-
sist in external applications for the de-
struction of the parasites and not in
ternal remedies to purify the blood
Drs. Salmon and Stiles in fourteenth
annual report of the Bureau of Animal
Industry