Evening star. [volume] (Washington, D.C.) 1854-1972, 1931-01-11
FEVER INVASION
OF EAST FEARED
Tick Which Carries Rocky
Mountain MaIady Gradually
Extending Range.
BY THOMAS r. HENRY.

Rocky Mountain spotted fever,
dreaded malady somewhat similar to ty-
phus, which hitherto has been almost
sntirely confined to the Rocky Noun
tain area, now may be in . position TO
Invade the East.
The gradually extending range Oh the
PARASITIC tick which carries TINS olsease,
n is reported at the National AnsCItuIe
of Health, finally has crossed the [anse
of another tick so similar In every ae
epect that only Specialist can olS. ~,
v1Iisl the two. This is the common cog
Hclr PREVALENT among dogs all over the
country east of q line extending nortn
and south from West Texas to the "a
totas It has been demonstrated In the
MIGRATORY that the dog tick can become
iY1fected and carry the disease. IL Is
probable that this also can happen III
The range of the dog tick stops rather
abruptly at the eastern toothllls OF Inc
Rockies, probably due to some chnlatic
factor highly unfavorable to its exist
ence. This parasite also ranges over
considerable area in Cali1ornia, WneLe
dnrs have been carried by settlers from
tine East. and in small islands in the
mountains where the specific climatic
factors apparently do not obtain. While
the tick responsible for spotted fever
has been studied intensively, very little
is known Of the behavior and charac-
teristics Of the dog tick and Public
Health Service specialists are planning
a program Of intensive research in this
direction. What is known Of its life
history corresponds closely with that
Of the derrnacentor anderson which
carries the spotted fever.
Three Life Phases.
The life Of the latter Is in three
phases, larva, nynph and adult. The
larva after Matching attaches itself for
q few days to some rodent, such as q
rabbit or ground squirrel After gorging
itself with the animals blood it drops
on and undergoes its Ametamorphosis
into a nymph. Then 1t must again at
tach itself TO q rodent and feed on
blood before it metamorphoses into an
adult The whole process in nature re-
quires two years.
As an adult it attaches itself to some
large mammal, such as a COW or q
horse. But it also viii attach itself to
8 man. Neither the rodent nor the
large mammal contracts spotted fever,
which appears to be an exclusively
human disease. But both get the causa-
tive agent in their blood and pass it on
to the succeeding generation of ticks
in an endless cycle. The tick seldom
passes directly from the large mammal
TO man, but 1t exists on vegetation
In such enormous numbers that persons
living In q tick locality can hardly
escape. The disease does not pass from
man to man. The dog tick nymph also
netamorphoSes into the adult tick on
the vegetation. A single female lays
from 5000 to 1000 eggs. Man Is an
accidental host, but frequent one.
An effective vaccine against spotted
fever infection, developed by DR.. r. r.
Spencer Of the National Institute Of
Health, has been In use for some years,
but its manufacture Is extremely time
consuming. The specific agent Of the
disease cannot be determined, % the
vaccine must be made by raising the
ticks themselves from larvae to adults,
the process. being speeded up in the
months. The adult, harmless at first,
becomes so virulent after feeding on
9 guinea pig for 1ve days, that single
individual Is SUFFICIENT to immaculate
$4,000 guinea pigs. From 10000, 900
larval ticks, on account of the high
death rate In rearing, about 100, 200
cubic centimeters Of vaccine is made
from the bodies Of the infected insects.
Several States Covered.
The spotted fever tick covers q range
consisting roughly Of Montana, Idaho.
wyoming and parts Of Colorado, Utah
ana washington, but recently the dis
ease has spread as far south as Arizona.
requiring q more extensive distribution
OF the vaccine. The vaccine itself
varies In its effectiveness according to
tne locality. Just Is the fever varies
most curlouSly In Yirulence, It Is en-
trely preventative and not a cure.
NO cure Is known, except to let nature
take its course
In some localities, it is pointed 2t by
DR.. r. r. Parker of the National In
stitute Of Health, now In charge of
spotted lever research, the disease Is so
mild that 1t almost never causes a
1atanty ana persons may even have it
without knowing 1t. In other restricted
iocaltleS the mortality may run as high
as 30 per cent Use for six years of
the vaccine in the mild areas" saws
DT. Parker, has demonstrated that II
VII entirely prevent the occurrence of
the disease. In the areas of high Ynor
tahty 1t markedly hghtens the effect of
the malady 80 that deaths are infre-
quent.
East of the Dskotas only one case
has been found TO date. This occurred
~ Indiana in 1924 and met all the
tests for spotted fever, although the
diagnosis was not absolute. How II got
there nobody knows.
Because Of the spread of the disease
plans now are under way for the Fed.
eral Government to take over entirely
the vaccine laboratory which Hitherto
has been maintained by the State of
Montana, except for the personnel fur
ntshed by the National Institute Of
Health.
The range Of the malady does not
spread rapidly, although in Montana it
mas spread from four counties in 1914
TO IS counties today. -Four hundred
persons were sick in Idaho in one year.
But National Institute of Health spe-
cialists see no immediate cause for
alarm in the present spread and timely
recognition Of the overlapping of the
ranges Of the two ticks may Be q sig
nincant factor In keeping the disease
Ia check.