300 
PACIFIC SCIENCE, Vol. XII, October, 1958 
quiries on cercarial dermatitis: Dr. W. R. 
Giedt, chief of Division of Epidemiology and 
Laboratories, Department of Health, Wash- 
ington; Richard F. Peters, chief of Bureau of 
Vector Control, and Benjamin Keh, assistant 
vector control specialist, Bureau of Vector 
Control, Department of Public Health, Cali- 
fornia; Ralph B. Williams, director of Division 
of Public Health Laboratories, Alaskan De- 
partment of Health; Curtiss M. Everets, 
Jr., director of Division of Sanitation and 
Engineering, Oregon State Board of Health; 
Dr. W. E. Martin, professor of zoology and 
chairman, Department of Biology, University 
of Southern California; and Dr. H. F. Hsu, 
research assistant professor, Department of 
Hygiene and Preventive Medicine, State Uni- 
versity of Iowa. Special thanks are offered 
Dr. J. R. Audy, of the Institute for Medical 
Research, Kuala Lumpur, Federation of Ma- 
laya, for suggesting the preparation of this 
report and for the invitation to participate in 
this symposium, General Ecology of Man, 
Animal Reservoirs, and Vectors in Relation to 
Disease, at the Ninth Pacific Science Congress. 
A. FRESH- WATER CERCARIAL DERMATITIS 
1 . United States and Canadian Pacific Coasts 
The etiology of swimmer’s itch was first 
elucidated by Cort in Michigan, U. S. A., in 
1928. Since that time, it has been recognized 
that "nonhuman” species of schistosomes 
are responsible for many cases of swimmer’s 
itch. In the United States and Canada, Jarcho 
and Van Burkalow (1952) indicated recently 
in their report that "the states most strongly 
affected are Michigan, Wisconsin, and Min- 
nesota. A few clinical cases (cercariae not 
identified) have been reported from the 
neighboring states of Indiana, Illinois, Iowa, 
Nebraska, and North and South Dakota. In 
Canada the major areas are in Ontario, east of 
Georgian Bay; in Manitoba, in and near 
Lake Winnipeg; in Saskatchewan; and in Al- 
berta.” Other areas mentioned in the text in- 
clude: British Columbia, Washington, Ore- 
gon, Quebec, New York, Maine, Nevada, 
Oklahoma, Alabama, Tennessee, and" Florida. 
The disease is common in lakes and swamps 
along the fly ways of migratory water fowls. 
Recent data, together with previous re- 
ports relative to the following Pacific states, 
are given as follows: 
a. Washington . Miller (1925, 1927) was first 
to describe the presence of schistosome cer- 
cariae in the northwestern United States. 
Cercaria elvae from Lymnaea stagnalis Linn, 
and Cercaria tuckerensis from Planorbis spp. 
were obtained from Trout Lake, San Juan 
Sound, Washington. Swimmer’s itch in the 
Seattle area was shown by Hunter, Shillam, 
Trott, and Howell (1949) to be caused by two 
agents: (1) the cercariae of Trichohilharzia 
ocellata (La Valette) ( = C. elvae) from Stag- 
nicola palustris nutaliana , and (2) Cercaria 
physellae of T. physellae (Talbot) from Physella 
propinqua (Tryon) . The former species of snail 
was found associated with reeds and other 
aquatic vegetation. growing in the gravel and 
mud bottom of the Jake. It was thought that 
the cercariae from infected snails were carried 
to shore by currents created by the wind 
blowing towards the beaches. A similar situ- 
ation was known to have existed in Douglas 
Lake, Michigan (Cort, 1936). 
The definitive hosts for these parasites in 
Washington have not been described, but, 
according to McMullen and Beaver (1945), 
C physellae , whose definitive host was re- 
ported to be the blue-winged teal, Querquedula 
discors (Linn.), was also infective to pigeons, 
mallards, and canaries; however, a Caspian 
tern, chickens, domestic ducklings, and gulls 
could not be infected. The blue- winged teal 
is also the definitive host of T. ocellata (=T. 
Kossarewi ), but McMullen and Beaver showed 
that canaries, domestic ducklings, mallards, 
and pigeons could be the experimental hosts. 
(Chicks and a tern were resistant.) Recently 
Farr and Blankemeyer (1956) described a new 
species of schistosome, Trichohilharzia hran- 
tae , whose definitive host was a Canada goose 
( Branta canadensis L.) from the Turnbull Na- 
tional Wildlife Refuge, Washington. 
