It’s a beautiful day. The water is inviting. The sun is shining. No wetsuit is required. You wade into the shallows. The water feels silky on your skin. The quack of nearby ducks adds to the idyllic scene – but what’s in their poo and why should you care? Swimstaman explains
The water is lovely this time of year, isn’t it? Even those who aren’t hardened winter swimmers will dust of their costumes and wade into the glorious warmth of that deep summer liquid.
Now allow me to introduce to you a Latin word you may not have heard of: Cercariae (from the Greek word for tail). What are Cercariae? Here in Switzerland people commonly refer to them as ‘duck fleas’ or ‘puces de canard’ but they are known internationally by the terms ‘Swimmer’s Itch’ or ‘Swimmer’s dermatitis’. Considering how often I swim, I’ve been lucky to only encounter them now, after twelve years of swimming here.
It was a beautiful day at Lake Lugano. I swam across the Italian border, I got out, got dressed, and continued hiking. By evening, I noticed a few mosquitoes buzzing around and looked at my ankles thinking, ‘wow, I’ve been heavily bitten!’ It wasn’t until the next day that I noticed that the bites were actually more like a rash. Then the rash got worse, and I noticed more patches over my body: armpits, shoulders, back. Very itchy! Nearly three weeks later evidence of these ‘bites’ remained.
What happened? This was my first encounter with duck fleas. These are not fleas at all, but the larvae of a duck parasite that is transmitted via duck poo. The eggs, upon leaving the poo, hatch and start to grow within a mollusc. They leave the mollusc and enter the water as Cercariae. There, they burrow into your skin but, unable to live there, drop out again. This leaves your skin red and itchy. It sounds pretty bleak but, other than a tolerable itch, it’s not so bad.
“These are not fleas at all, but the larvae of a duck parasite that is transmitted via duck poo. The eggs, upon leaving the poo, hatch and start to grow within a mollusc. They leave the mollusc and enter the water as Cercariae. There, they burrow into your skin but, unable to live there, drop out again. This leaves your skin red and itchy.”
The easy ways to avoid them are:
– shower immediately after swimming
– avoid the shallows/areas where ducks are and where the water is warmest (reports suggest they prefer water of 20 degrees and above)
– dry yourself vigorously with a towel
– in addition, swimming further out where it’s cooler, and entering the water away from the shallows will help
My additional suggestions are purely anecdotal: on the day I developed swimmer’s itch, I was swimming with a friend who was wearing sun cream that happened to be anti-jellyfish and was wearing tight, jammer-style trunks. He didn’t get a single bite! I, however, did everything wrong. It was 30+ degrees out so I didn’t shower, and I didn’t dry off. I was swimming in the same shorts I was hiking in. I was wearing no sun-cream (other than my neck and face; some sources suggest that sun cream can help deter the parasites, but do bear in mind you then have the environmental question of using that cream within a natural body of water). I was affected all over, including in the loose areas around my shorts, as if the parasites were actually caught and carried in my shorts.
Also bear in mind that, due to the warmer water, and being closer to the shallow living/sleeping/nesting spots, children’s swim areas can be particularly populated with duck fleas. Here’s to a fun and itch-free Summer of swimming outdoors!