Pacific Area Distribution of Fresh-Water and 
Marine Cercarial Dermatitis 1 
George W. T. C. Chu 2 
Cercarial dermatitis, a form of "swim- 
mer’s itch," is a skin infection caused by the 
penetration of schistosome cercariae. The 
disease is also known as schistosome derma- 
titis. The clinical symptoms start with an 
itching sensation, which is followed by the 
development of a rash or petechiae, and in 
many hypersensitive persons papular erup- 
tions appear together with intensive itching 
and edema. It is a self-limiting ailment if no 
further infection is contracted. It is neither a 
communicable disease nor a fatal one, but the 
discomfort and the pathology of the infection 
contribute to its importance in the field of 
public health and veterinary medicine. 
The disease is of geographical interest be- 
cause it is a "Disease of the Place," as ex- 
plained by Jarcho and Van Burkalow (1952). 
Normally the adults of the dermatitis- 
producing schistosomes are blood parasites 
of birds, or, in some instances, of mammals. 
The life cycle begins with the hatching of the 
eggs which are present in the droppings of 
infected animals. Suitable species of snails be- 
come infected upon contact with the mira- 
cidia hatched from the eggs, the snails serving 
as the intermediate host. After a proper incu- 
bation period in the snail, the infectious 
schistosome cercariae are issued into the sur- 
rounding water. Upon exposure to these 
cercariae, the bird or mammalian definitive 
hosts are infected and the parasites mature in 
the vascular system of the hosts. The life 
1 Presented in the symposium, General Ecology of 
Man, Animal Reservoirs, and Vectors in Relation to 
Disease, the Ninth Pacific Science Congress, at Bang- 
kok, Thailand, November 12 — December 9, 1957. 
Contribution from Hawaii Marine Laboratory No. 
110. Manuscript received November 7, 1957. 
2 Departments of Bacteriology and Zoology, Uni- 
versity of Hawaii, Honolulu, T. H. 
cycle is completed when the adult worms 
produce eggs. Humans contracting the cer- 
carial dermatitis are only the result of acci- 
dental intrusion into the life cycle of these 
interesting parasites. 
Therefore in any geographical area, the 
conditions responsible for the occurrence of 
cercarial dermatitis are: (1) the presence of 
birds infected with dermatitis-producing 
schistosomes, (2) the presence of the snail 
intermediate hosts with habits conducive to 
the acquisition of the disease, (3) ecological 
conditions favorable for the survival of both 
the hosts and the parasites, and (4) the pres- 
ence of human beings engaged in an activity 
which exposes them to the infection. In many 
parts of the world these four basic factors are 
present, and, as a result, the distribution of 
cercarial dermatitis is worldwide (Cort, 1950; 
Kuntz, 1955). 
In the Pacific area, the disease occurs at 
various locations on the west coast of the 
North American continent extending north to 
Alaska. It has been reported from Japan, the 
Federation of Malaya, Australia, and as far 
south as New Zealand. The Hawaiian Islands 
chain is not entirely free from the presence of 
this disease. The following report is an at- 
tempt to summarize from the literature 3 the 
important facts concerning the vectors and 
reservoir hosts of cercarial dermatitis and to 
emphasize the distribution and transmission 
of both fresh-water and marine schistosomes 
in various parts of the Pacific. 
ACKNOWLEDGMENTS 
The author gratefully acknowledges the 
assistance of those who responded to his in- 
3 The survey of literature on cercarial dermatitis was 
concluded in July, 1957. 
299 
