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My carelessness at the lake was swiftly punished by duck fleas

16/8/2024

Translation: Katherine Martin

If your cool dip in the lake turns into a bout of itchiness, you might have been attacked by duck fleas. Though they’re usually harmless, these parasites are super annoying.

The other day at Lake Zurich, my friend insisted on going to a spot with shower access. Her reasoning? Apparently, she urgently needed to rinse off straight after swimming. «Huh? Chill out, it’s just lake water,» I said. «What about duck fleas?» she replied. I’d never heard of them, so I was all the more optimistic that nothing would happen to me. Alas, my friend turned out to be right. The critters well and truly laid into me, attacking me from head to foot.

Don’t duck fleas only infest ducks?

Not exactly. The parasites live in ducks’ intestines, and their eggs are released into the lake when the ducks poop. The larvae then hatch and infest water snails. If the water rises above 20 degrees, the larvae abandon their host and go in search of new waterfowl, beginning the cycle all over again.

Unless, that is, you swim by at the wrong moment, and the parasites mistake you for a duck. If that happens, they’ll try to burrow their way through your skin. Thankfully, they won’t get far because human skin is too thick for them. Instead, the duck fleas get stuck, before being killed off by your immune system. What remains is an irritating, but in most cases harmless cercarial dermatitis, also known as swimmer’s itch (website in German).

The parasites are called cercariae, but are sometimes referred to as duck fleas.
Source: impuls.migros.ch

I’m itching all over. What should I do?

When the itching sets in, there’s not much you can do about it. It should disappear within one to two days, with the pustules also clearing up after 10–20 days at most. If you can’t stand the itching, the University of Zurich recommends using prescription lotions that contain polidocanol or over-the-counter anti-allergy meds.

Body lotions

Mavena B12 lotion

Body milk, 200 ml

Yuck! I never want these parasites to come near me

If that’s the case, rivers or mountain lakes at 1,500 metres above sea level are your only viable swimming spots. Still don’t want to miss out on a refreshing dip at your local lake? At the very minimum, you should avoid warm, shallow water. Especially places where there are a lot of ducks. Like my friend, you should take a shower right after swimming, rub your skin dry with a towel and change your clothes.

Two days into a bout of itching, I’ve certainly learned my lesson – and have been showering dutifully ever since.

Header image: Shutterstock.com

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Stefanie Lechthaler

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Stefanie.Lechthaler@digitecgalaxus.ch

Painting the walls just before handing over the flat? Making your own kimchi? Soldering a broken raclette oven? There's nothing you can't do yourself. Well, perhaps sometimes, but I'll definitely give it a try.

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