Prospective Study of Swimmer's Itch Incidence and Severity

Abstract

This epidemiologic study reports incidence, severity, and risk factors of swimmer's itch (cercarial dermatitis). Daily diaries about water exposures and swimmer's itch symptoms were completed by 40 riparian households at Douglas Lake, Michigan, for July 2000. Minutes spent in the water, minutes in shallow water, location, time of day, preventive action, age, and gender were recorded for all residents and guests. Incidence of swimmer's itch was 6.8 episodes per 100 water-exposure days. Probability of an episode increased with more days of water use and at locations with onshore winds. Episode severity increased with more time in the water and at the same locations. Age and gender had no effect on incidence or severity. In sum, onset and severity of swimmer's itch are affected by how people interact with the lake, not by their demographic features. More studies of human incidence and severity are needed to convince public health agencies to address this problem at recreational lakes. Study designs that combine epidemiologic and biological data will simultaneously inform public health education and biological control programs.

Avian Schistosomes and Outbreaks of Cercarial Dermatitis

“…Cercarial dermatitis develops as a result of sensitization of the human immune system (232,260), and repeated exposures to cercariae influence the occurrence and intensity of subsequent infections. For example, longer exposure in water increases cercarial penetration via frequent water visits and more time spent in shallow water (4,(304)(305)(306). While gender does not influence the risk of infection (4,304,305,307), some studies found a higher risk among children of less than 15 years of age, since they tend to spend more time in shallow water (280,308,309).…”

“…For example, longer exposure in water increases cercarial penetration via frequent water visits and more time spent in shallow water (4,(304)(305)(306). While gender does not influence the risk of infection (4,304,305,307), some studies found a higher risk among children of less than 15 years of age, since they tend to spend more time in shallow water (280,308,309). There are rare cases of nonsensitive individuals that may be due to host desensitization (310) or individual nonsusceptibility/nonattractivity to cercariae (4,311).…”

“…accumulate in vegetation-free areas, on stones or muddy sediments; and physid snails prefer detritus as a source of food (312,313). In addition, cercariae of avian schistosomes can be transported by wind and water currents for several kilometers (2,304,305). Therefore, taking the local situation into account is essential for risk assessment, because conditions unsuitable for one snail species may provide an ideal habitat for another.…”

“…Most cases of cercarial dermatitis correlate with high air and water temperatures during the summer months, when schistosome development in snails is amplified and emission rates of cercariae are stimulated by sunlight (4,11,279,280,304,305,309,314). Production can reach several thousands of cercariae/snail/day (169,300,315), and these emission rates may even counterbalance the loss of cercarial capability to survive and infect hosts at high temperatures (see above).…”

Cercarial dermatitis in Austria: Questionnaires as useful tools to estimate risk factors?

“…Due to the fact that our knowledge about human incidence and risk factors is rather limited in Central Europe [12] and even in the world [13][14][15], a website [16] was created in spring 2003 with information for persons concerned, combined with the option to download a questionnaire to provide us with first-hand information.…”