332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1947 



cies nearly always seeks out the river snails of the Thiarid family. In 

 contrast to the simple schistosome life cycle, the lung fluke spends 

 only a part of its larval life in the snail, and then emerges again to 

 seek out a second intermediate host, this time a fresh-water crab or 

 crayfish. The crustacean must be eaten raw by man in order that 

 the lung-fluke larvae may penetrate the intestinal walls and migrate to 

 the lungs. One marvels that such a disease can continue to flourish 

 with so many weak links in its long and complicated life chain. In 

 the Shoahsing area of Chekiang Province, China, famous for its good 

 wines, a large proportion of the population is infected with lung flukes 

 because of the native custom of eating uncooked crayfish that have 

 been dipped in wine. 



Peculiar and unchangeable eating habits of man are again respon- 

 sible for the world's largest endemic area for the bile-fluke disease 

 which afl:'ects several million people in the Canton areas of southern 

 China. The life cycle of this fluke worm includes a mammalian host, 

 usually man, dogs, or cats, a first intermediate snail host, and a second 

 intermediate fish host. The infectious larval stages of the worm are 

 embedded in the flesh of the fish, and must, as in the case of the cray- 

 fish, be eaten uncooked. Raw fish is consumed as a delicacy by the Can- 

 tonese during the fall festival season. Strips of the more succulent 

 parts of the fish are dipped in hot tea or hot rice gruel, and are thus 

 only partially cooked. Many of the natives cannot afford sufficient 

 fuel to cook the fish thoroughly, and thus become infected. 



THE SNAIL PROBLEM IN THE UNITED STATES 



No sooner had the schistosomiasis epidemic among our troops in 

 the Philippine Islands been quelled, when Public Health authorities, 

 under the leadership of Dr. Willard Wright, turned their attention 

 toward the possibility of an outbreak in our own country. Although 

 schistosomiasis has never been contracted in the United States, the 

 recent return of infected service personnel presents a potential threat. 

 To determine whether or not domestic species of snails are capable of 

 serving as intermediate hosts, Dr. Eloise Cram, parasitologist, and 

 Dr. Elmer Berry, malacologist, have been carrying out an intensive 

 study of this matter. Living specimens of many of our American 

 species are shipped from the field to the aquarium rooms of the Na- 

 tional Institute of Health in Bethesda, Md. There they are exposed 

 to the various trematode diseases under study. 



Already, one species of Tropicorbid snail sent in from Louisiana has 

 been shown to be capable of acting as an intermediate host of Manson's 

 disease. The native habitat for this species is the island of Cuba, with 

 a few scattered records in Louisiana and Texas. These latter records 

 may represent accidental introductions by man. Laboratory infec- 



