Glorious summer weather is not only ideal for swimmers, pesky duck fleas also thrive in high temperatures. They lie in wait for their victims in local waters and cause severe itching. This is a case of mistaken identity: the parasites cannot distinguish between humans and animals.
Strictly speaking, duck fleas are not fleas, but larvae of sucking worms, also known as cercariae. These live as parasites in the intestines of native ducks, geese and swans. The worm eggs enter the lakes via the droppings of waterfowl. When the larvae hatch, they are the first to attack water snails. At water temperatures above 20°C, the larvae (cercariae), which are around one millimeter in size, leave the snails and set off in search of a host.
“In the worst cases, patients don’t close their eyes at night because of the itching.”
Annoying, but harmless
If a person happens to swim past, it becomes unpleasant for them. This is because the larvae cannot distinguish human skin from duck skin and try to bore into it. But human skin is too thick for the larvae – they get stuck in it and are killed by our immune system. They cause so-called bath dermatitis, which manifests itself as a red skin rash with severe itching, urticaria, burning, tingling and numerous pustules and small blisters. It should be noted: The symptoms caused by duck fleas are basically harmless. But the annoying itching can last up to two days, and the inflammation only heals after 10 to 20 days without treatment.
How to treat duck fleas
“How annoying the itching is perceived to be varies from case to case,” says Claudia Lang, senior physician at the dermatology clinic. “Like pain processing, itch processing is very individual. Patients who get itchy for the second time can react very strongly, as the immune response can be more severe the second time. In the worst cases, patients don’t close their eyes at night because of the itching, which of course has an impact on everyday life.”
In addition, there is a small risk of secondary infections due to vigorous scratching, similar to mosquito bites. Not every encounter with duck fleas has to end in pustule horror. “There are tablets and ointments that relieve the itching,” explains Lang. “If someone is suffering really badly from itching, we can prescribe lotions with polidocanol. This is a local anesthetic that soothes the skin. There are also anti-allergic tablets, known as antihistamines, which help to relieve the itching. Some are even available over the counter.” Fortunately, bath dermatitis is not contagious.
What helps against duck fleas?
The best thing to do is to take precautions: avoid bathing areas with particularly large numbers of waterfowl, as duck fleas can be found there as well as in shallow, warm water. In addition, the pests can be prevented from penetrating the skin by showering thoroughly after bathing and drying thoroughly. If you want to be on the safe side, you should only swim in flowing waters. Duck fleas are not an issue in rivers. This is also the case in the sea: the parasites do not survive in salt water.
Five simple tips against duck fleas
- Do not swim where there are many water birds
- Shower thoroughly immediately after swimming
- Rub dry vigorously with a cloth
- Avoid warm and shallow water
- Change clothes after swimming
