The Control of Swimmer ' s Itch in Michigan : Past , Present , and Future

The association between a type of dermatitis known as swimmer's itch and the free-living stage of certain digenetic trematodes (nonhuman schistosomes) was delineated in 1928 by Cort at the University of Michigan Biological Station. Following his discovery, studies on swimmer's itch have continued at the Biological Station until the present time. In 1939, the State of Michigan initiated a control program that included the application of copper sulfate to many of the larger recreational lakes. It was assumed that this molluscicide would reduce the prevalence and incidence of swimmer's itch by interrupting the life cycle of the parasite in the snail intermediate hosts. Unfortunately, swimmer's itch continues to be a problem in Michigan despite more than a half century of control efforts. In addition, concerns about the accumulation of toxic copper sulfate in our aquatic ecosystems are being expressed more frequently. In 1985, Blankespoor initiated a new approach to the control of swimmer's itch by treating the definitive host with an antihelminthic drug, Praziquantel. Based on four years of research on Glen Lake, the authors have concluded that controlling swimmer's itch with Praziquantel is more effective than using copper sulfate, less expensive, and has no detrimental effects on the environment. In 1990, the program was expanded to include three additional lakes in Leelanau County, Michigan.