Clinical Images: Cercarial Dermatitis

Cercarial dermatitis (or swimmers' itch) is a self-limited, non-communicable water-borne disease, which is usually caused by penetration of the skin by larvae of avian parasitic flatworms (schistosomes). Free-swimming cercariae larvae are released from various snail species, and penetrate into the skin of compatible definitive hosts (usually birds and waterfowl), where they develop into adult flukes and produce eggs.¹ Cercarial dermatitis occurs when cercariae accidentally penetrate human skin. Human skin is unsuitable for avian schistosomes, and the parasite dies within the skin.² Primary infections usually present with an initial tingling sensation on exposed areas, followed by formation of pruritic macules and/or papules within 12-24 hours (up to 8 days). Repeated infections cause a more pronounced skin reaction. The papules usually regress leaving hyperpigmented macules over 4-10 days (up to 20 days).¹