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51
Prevention of Diphtheria and Scarlet Fever.
Diphtheria in spite of our knowledge of its causation and
in spite of the specific treatment by means of anti-toxin still remains
a baffling disease to control and at the same time an anxious disease
to treat because of its high mortality. No doubt the death-rate
from diphtheria is now one-third that of 50 years ago, chiefly due
to the use of anti-toxin, but the disease is still prevalent, and there
has been little decline in its prevalence and mortality in the last
ten years. It is chiefly on account of its high mortality that our
anxiety for its control arises.
Scarlet fever on the other hand continues to be prevalent
but fortunately the mortality has decreased and continues very
low. In epidemic times, however, so great is the dislocation of
social and commercial intercourse and so great is the expense of
isolating actual cases that any suggestions for the control of the
disease should be considered in a thorough and broad minded
manner.
As bacteriological swabbing and anti-toxin treatment have
failed in quelling diphtheria investigators have cast about for some
other means of control. Schick put forward in 1911 the test which
has now acquired his name and by means of which the susceptibility
of individuals to the disease can be determined. This consists in
the injection into the skin of a small amount of diphtheria toxin.
If the person is susceptible to the disease, in other words if the
person does not possess sufficient immunity, certain appearances
become evident round the point of injection within a short space
of time.
This test was taken up by Park and Zingher in New York
and further developed and carefully applied to a large number of
persons, chiefly children, the result being that there have been
many definite observations made along the lines of Park and
Zingher in many parts of the world.
Reaction.—If the blood of the person injected contains insufficient
anti-toxin, the toxin introduced is insufficiently neutralised
and therefore causes reaction in the tissues.