Great Falls tribune. [volume] (Great Falls, Mont.) 1921-current, 1922-07-12

oped within 10 days, the contents OF
the same ticks were innoculated. .
I'm a few days many pigs SO treated
developed spotted fever, some after
feeding and others after the %innocula-
ton.
"On the other hand, the infectivity
tests carried out on ticks picked from
animals (which are of course engorged
or partially e%ngorged) have given diff
ferent results. Here, the innoculation
of tick contents alone is apparently
6 reliable indication of tick infectivity
and no difficulty has been experienced
in obtaining typical spotted fever in
animals SO i~nnoculated.
Need Animal Blood
THE simplest Interpretation of these
results is that the virus in the unfed
adult ticks which remain over winter
or through other long periods is in a
dormant or non-virulant stage. which
requires fresh animal blood for its
revival. Apparently, the virus is not
infected until the tick partially en-
gorges and in this way furnishes it with
the needed stimulus, yet, prior to en-
gorgement. the virus in the tick does
possess immunizing properties, as
shown by numerous tests.
Immunity in animals Ear also be
produced during the egg stage Of the
tick as first shown by an experiment
of Ricketts,. Ricketts, produced spot
ted fever by the injection of eggs of
infected females, using from 8 to so
eggs to an injection. 1t is important
to note that these eggs were less than
a week old. With eggs that had been
dried for four months, immunity and
not fever developed.
I'm an attempt to cultivate the virus.
Ericks in 1915 innoculated infected tick
eggs which had been incubated with a
special culture media for % days, and
produced immunity in the i~nnoculated
guinea pigs.
Last winter DIR. Parker also pro-
infected Eggs of the rabbit tick which
were three months old.
These experiments. in the light of
our work this spring, appear more sig
n~ificant than formerly and we are now
in the midst of other investigations
which. it is hoped. will throw more
light upon the various stages of the
spotted fever virus N the tick. The
further study Of this apparent non
virulant. neutrality-suspicious. phase that
the virus passes through in the tick
body and in the eggs is very promising.
VIII Produce Immunity
There is no reason to doubt that.
finally. conditions can be so controlled
as to invariably produce immunity.
Such immunity is. of necessity. an ac-
tive one. and therefore it is reasonable
to regard it as more or less lasting.
AT the present moment our knowl-
edge is too meager to discuss the pos
sibility of immunizing human beings
DIR. Parker's address follows:
Rocky Mountain spotted fever is q
rodent disease which existed before
persons. and human infection is an
accident in all cases. Its control de-
mands a thorough knowledge of the
natural factors which permit ii to exist
and which perpetuate it.
The work Of control in the Bitter
Root valley has been going on for eight
years. without the necessary fundamen-
tai knowledge and the full realization OF
the pressing need for research. The
greatest fault with the control was the
lack of ~permanency.
With the cooperation of the United
States public health service at the be-
ginning of September of 1921, a sys-
tematic investigation became possible
There are two main lines by which
spotted fever may be studied, n which
deals with the meteorological phase and
the other which concerns the study OF
the disease in nature.
The objects of a study under the
second phase arc TO find out if there
is a feasible method Of control, if more
permanent methods can be secured
and to find a feasible means of control