The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1941-07-31
REPORTS ON
SWIM ITCH
DR.. Thompson Explains Attic
ton That Often Comes From
States Lakes.

States Lakes.
The short time stitch" that has in
fected bathers in several lakes of
Michigan, Wisconsin and Minnesota
for the past few years has been studied
and the cause separated.
DR.. j. E. Thompson, city veterinarian,
reported on the matter and his find
ings at special session of the city
council and the health officers on Mon
day evening as follows:
Explanation of Swimmers Itch"
(SchistOsome Dermatitis)
The summer season has been known
to produce various forms of human
skin irritation and in all cases the
cause has not been definitely known
In 1928, DR.. Cort of Johns Hopkins
University while mentioning at Lake
Douglas in Michigan gathered snails
and noticed that he got an intense
itching of his hands and later skin
eruptions resembling mosquito bites.
Since then much work has been done
on the subject and the condition has
been definitely proven as existing and
having existed for years in Michigan,
Wisconsin and Minnesota lake regions.
Each investigator has added more to
the study of the spread and protection
against this particular Itch"
Briefly what takes place is as fol-
| lows:
It is necessary that there be GER
tain species of snailS in the vicinity,
though it is possible that other mol
luks may play a part in the life cycle.
Only small percentage of the snails
in the snail bed will be infected, but
each infected snail will daily give OH
large numbers of cercariae or larvaie
which are microscopic. These cercariae
will come to the surface and they
maintain activity with Tipping action
of forked tail, searching for warm
blood host to attach to. They have
very fine spinius processes along thef
outer surface, and with the aid Of
these and a leech-like suction they
penetrate the hair pores much a:
though they were a minute porcupine
quill. The skin sets up defense re-
action and the result is small red
dish swelling with itching that ma!
last several days. Apparently this il
all that takes place in the human
skin and the larva family dies in tn,
pore and is thrown off. There is no evi
dence that the type of cercariae from
the schistosomes found in our northern
lakes ever reaches the human bloot
stream.
It is different with other animals
Ducks and muskrats have been known
to harbor the adult stage of the schis
tosome in their blood stream. Tha
:. is, the same cercariae which attack
our skin and produces the "itch
enters the ducks and muskrats il
some manner and grow to maturity
They then in turn lay eggs which ar
; passed out through the bile duct int
the intestinal canal and the eggs final
. ly reaching the water with the bowe
discharges. The eggs undergo hatch
ing and are then taken up by tn
snails where in each egg develops to
sporocyst and then daughter sporo
cysts. Each sporocyst will then pro
duce enormous numbers of the larva
or cercariae which the snail will dis
charge daily into the water and ther
we have the cause of the itch.
The snails are usually found in shall
low sandy and weedy places. The Ger
: cariae will be found only in the i'm
. mediate vicinity of the infected snail
: and only a small percentage of tn
snails will be infected. Likewise onl
a small percentage Of the ducks ar
infected. The cercariae are discharge
after the middle of July and into tn
q first weeks of August. The snails di
annually and it is necessary that
: new batch of snails be born Tor tn
next season and a duck or muskra
with the adult schistosome in its bloc
i stream come along and infect the snail
i the following years.
The water out ways from the in
fected snail bed is not contaminate
> with the cercaiae so that only the i'm
: mediate vicinity of the infected snail
u is a source of the itch. Likewise, tn
cercariae are very delicate and rub
bling with a coarse towel will destro
= the cercariae before they become lodge
in the pores If one dries off withou
the use of a towel after swimming
then if the cercariae were there, tn
itch will show up. 1t does not folio
that the same snail bed viii agai
l next year have the itch producin
L cercariae, because the proper infecte
ducks or muskrats happened not to b
> there.
!. Many lakes in Minnesota and neigh
L boring states are known to have ha
infected snails, and judging from re
ported itch cases there are other lake
. with infected snails but only a tediou
search of hundreds of snails take
from such places could give definit
evidence. The area in the immediat
vicinity of the aeroplane docks o.
Shagawa Lake definitely is one spo
' The best advice for bathers is to see
places for swimming where there ar
, no snails, deeper water in particula
is usually safe. The use Of towe
. after swimming will further safeguar
the bather but if one is in and on
of the water all afternoon and the
uses a towel to dry with, I doubt if
: will be effective.
Most of us remember as youngster
that at this season of the year W
used to say, Don't go in swimming