Cercarial dermatitis(swimmer’s itch)

• acute dermatitis caused by contact with schistosomes in warm freshwater lakes
• Symptoms may begin within minutes or as long as two days after swimming or wading in contaminated water.
• Usually the rash affects skin that’s not covered by swimsuits, wetsuits or waders

caused by

• Schistosomes are parasitic flatworms with a lifecycle that involves aquatic birds (eg, ducks, geese, gulls, swans) or mammals (eg, beavers, muskrats), specific species of aquatic snails, and warm fresh or salt water.
• The adult worm lives in a bird/animal, and the eggs are excreted via the intestines in the faeces.
• An egg hatches in the water to become a free-swimming miracidium in search of a specific snail species.
• The miracidium enters the snail, elongates into a sporocyst, then matures into a cercaria which burrows out of the snail into the water.
• Cercariae may penetrate the skin or are ingested by the aquatic bird/animal, develop into an adult worm, and the cycle starts again.
• Cercariae may accidentally attach to human skin, penetrate the skin, die, and cause a local allergic reaction

Preventative measures

To reduce parasite numbers in the environment:

• Avoid bird-feeding where people swim
• Feed birds with a drug to treat the parasite
• Reduce vegetation in high-risk areas to make the environment less favourable for the water snails
• Use of chemical molluscicides such as copper sulphate or copper carbonate in small lakes to kill potentially infested snails.

To reduce the risk of cercariae on the skin:

• Immediate towelling after exiting the water to reduce skin penetration of the parasites
• Avoid swimming in shallow warm waters.

Symptomatic measures for itch and rash

• Soothing applications
  • Calamine lotion
  • Colloidal oatmeal soak
  • Baking soda paste
  • Cool compress
• Topical steroids
• Systemic treatments
  • Oral antihistamines
  • Short course of oral corticosteroid for a severe reaction
  • Antibiotics for secondary infection

outcome

• Swimmer’s itch usually resolves within 1–3 weeks without treatment. However, repeated exposures can result in severe reactions.