Cercarial Dermatitis — Chu 
301 
Macy (1952) demonstrated that C. elvae 
from Lymnaea stagnalis was the causative 
agent for dermatitis cases at Cascade Lake, 
Orcas Island. Macy (1955) further reported 
that dermatitis cases were found at a lake 
south of Tacoma, Washington, and from Lake 
Chelan and Goose Lake, Okanogan County, 
in eastern Washington. In spite of the fact 
that a large number of lakes in the state of 
Washington might have harbored schisto- 
some-infected snails, Dr. W. R. Giedt, chief 
of Division of Epidemiology and Laboratories 
of the Department of Health, received only 
ten reports of cases in 1955 and ten during 
1956 (personal communication, 1957). Since 
swimmer’s itch is not a reportable disease, 
these statistics are probably incomplete. How- 
ever, the preventive measures advocated by 
the health officers of Washington with regard 
to control and avoidance of the infection 
must have been successful, as is indicated by 
the low incidence of infections. 
b. Oregon. Macy (1955) investigated schist- 
osome dermatitis cases in the Blue Lake area 
near Troutdale, Oregon. The causative agent, 
C. oregonensis from Physa ampularia , was a 
schistosome species originally described by 
Macfarlane and Macy (1946). It is interesting 
to note that these infected snails occurred 
most abundantly on dead or decaying vegeta- 
tion in lakes, ponds, and marshes. They laid 
their eggs in late summer and the next gen- 
eration of snails matured enough to lay their 
eggs during the early spring. Snails infected 
during late summer could carry the schist- 
osome through the winter; thus in the follow- 
ing spring and summer, infected snails of 
both the old and new generations might 
produce cercariae for a longer time and there- 
fore possibly might cause a higher level of 
infection in humans. 
c. California. Simmons, Martin, and Wag- 
ner (1951) reported that the first case of fresh- 
water cercarial dermatitis in California was 
derived from an artificial lake at Alendra Park 
in Los Angeles County. Schistosome cercariae 
of three different types were obtained from 
Physa osculans (Haldeman) found in this lake. 
The taxonomic consideration of these cer- 
cariae is currently delayed because of the effi- 
cient control of the intermediate hosts by 
health officers (personal communication from 
Dr. W. E. Martin, 1957). Walker (1954) in- 
vestigated a suspected outbreak of schist- 
osome dermatitis at Twain Harte Lake, 
Tuolumne County, and found bifurcated cer- 
cariae coming from a mixture of Physella and 
Lymnaea snails. Taxonomic determinations of 
the schistosomes involved in these dermatitis 
cases are yet to be announced. Keh and 
Grodhaus (1957) reported swimmer’s itch at 
a duck club in Yuba County. Cercariae of the 
" ocellata ” group were obtained from Physa 
snails and later proven by experimental infec- 
tion to belong to the Trichohilharzia group of 
bird schistosomes. As yet, there is no report 
of schistosome infected snails or cases of 
cercarial dermatitis in northern California. 
d. Canada. As indicated previously, migra- 
tory water fowls such as the blue- winged teals 
are known to be the definitive hosts of 
dermatitis-producing schistosomes. Because 
of the many glaciated lakes and swamps 
which act as bird refuges, cercarial dermatitis 
in Canada is known to occur in many areas. 
Along the Pacific coast of Canada, only two 
species of dermatitis-producing schistosome 
cercariae have been reported. These cercariae 
were believed to be the agents responsible for 
a severe outbreak in 1950 at Cultus Lake, 
B. C. Edwards and Jansch (1955) described 
these two species as Cercaria adamsi and C. 
columbiensis , which have Physa coniformis Tryon 
as the intermediate host. The adult forms of 
C. adamsi are now designated as Trichobil- 
harzia adamsi Edwards and Jansch, 1955. The 
definitive hosts for C. adamsi were believed to 
be wild water fowl because domestic ducks 
could be infected experimentally. The authors 
suggested that the close resemblance of C. 
columbiensis to the cercariae of Gigantobilharzia 
huronensis Najim would indicate that the pas- 
