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I’d have to say this has been a funky summer for swimming. I happened to notice that the lake temperature crashed from 22C to 9C and back up to 22C within days during the first week of July. If you don’t believe me, check out the roller-coaster temperatures here on the Coupe de Noel home page.

The good news with these cooler temperatures is that the risk of attracting duck fleas should be lower. Duck fleas, or puces de canard, are a fact of life on lac Leman once the temperature of the water reaches 20C. A few interesting facts are:

  • They are not really fleas. They are a water parasite called Cercariae.
  • The parasite is found in the first 50 meters of water from shore and in mostly mossy and grassy areas.
  • The parasite develops in snails. Once it leaves its snail host, it floats to the surface to find a warm bodied host in which to lay eggs. They can penetrate bird skin and find their way into the blood vessels but can not get past human skin into our circulatory system.


  • The inflammatory response to this parasite trying to get into your system is not dangerous though you must be careful that you don’t get a secondary infection from scratching the irritated area. Cold compresses and Fenistil, an over-the-counter antihistamine Swiss people swear by, might relieve some of the itching.
  • Showering and rubbing off vigorously with a towel after swimming is a good preventative measure but not a guarantee.
  • Keep in mind that if you swim off a boat or padelo (the little paddle boats you can rent), you can avoid swimming along the shore line where the duck fleas live.

Cercaria of Austrobilharzia variglandis

That pesky parasite we call a duck flea.

For a more extensive explanation, check out the Center for Disease Control pages about the  cercariae  parasite here.

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