Symptoms
Bath dermatitis manifests as a red, inflamed, and allergic rash with a severe and uncomfortable itching sensation. Burning and tingling also occur. The injection sites of the cercariae are recognizable as reddened spots, papules, pustules or small blisters. Mild discomfort may already occur in the water, but symptoms develop with a time delay of several hours. The complaints are more pronounced in a second contact, which can be explained by sensitization and the development of an allergic reaction. Systemic complications such as dizziness, sweating, swelling, fever, nausea, and diarrhea may occur.
Causes
Bath dermatitis is caused by the microscopic cercariae that are found worldwide and also in Central Europe and in many countries. In many countries, for example, this includes . The cercariae are developmental stages of sucking worms of the schistosome family that infect some waterfowl and aquatic animals. Humans are infected as false hosts. The cercariae bore into the skin and die inside it. The inflammatory immune reaction is responsible for the skin reactions. Humans cannot pass on the disease because they are not the correct host. In everyday language, the cercariae are also called “duck fleas“. However, this name is incorrect and misleading because it is a sucking worm and not a flea. According to some experts, it has not been fully clarified whether the larvae are able to penetrate further and thus, even if they do not multiply further, may cause secondary symptoms (e.g., Horák et al., 2008, Kolářová et al., 2010).
Transfer
The adult parasite lives in blood vessels near the intestine in aquatic animals, especially waterfowl such as ducks, swans, gulls, and geese. Mammals such as beavers and muskrats can also be infected. The worm forms eggs that enter the intestine and are excreted in the feces. The eggs hatch into larvae, which infect the intermediate host, aquatic or mud snails. The larvae multiply and further develop into Y-shaped cercariae, which are excreted into the water in large numbers when the water temperature is high enough. Cercariae eventually re-infest the appropriate final hosts or humans as a false host.
Risk factors
- Bathing during the summer months
- High water temperature
- Hot summer
- Bathing in the early morning
- Risk waters
- Shallow waters without current
- Children, as they are mainly near the beach and often do not dry themselves with the beach towel
- Long duration of stay in the water
- Activities on the water, e.g. fishermen
- Individual susceptibility, repeated contact, sensitization.
Parasites cannot live in a well-maintained swimming pool, so there is no risk when swimming in a pool. There is also no risk in deep, cold or flowing water. Waters do not have to be permanently contaminated, as parasite infestation depends on various factors.
Diagnosis
Diagnosis is based on the patient’s history and clinical presentation and is usually straightforward. Differential diagnoses include other skin diseases such as insect bites and allergies.
Nonpharmacologic treatment
The rash will heal after days to weeks, even without treatment. Cold compresses or mild cold sprays can symptomatically relieve itching. If possible, do not scratch, as the small skin lesions can cause bacterial infections.
Drug treatment
Medications that are also used to treat mosquito bites can be used for treatment. These include: Antihistamines:
- Antihistamines such as mepyramine and diphenhydramine have antiallergic and antipruritic properties and are usually applied topically in the form of a gel or with the help of a roll-on. They are also combined with other active ingredients. If severe, they can also be taken in the form of tablets, drops or solution, such as cetirizine, loratadine or fexofenadine.
Essential oils:
- Essential oils and their components such as menthol and cineole have cooling, anti-itch, anti-irritant and antiseptic properties.Lotions are also available. Not all products are suitable for children.
Disinfectants:
- Disinfectants are applied for local prevention of infectious diseases.
Glucocorticoids:
- Cortisone creams and ointments with active ingredients such as hydrocortisone are anti-inflammatory, anti-allergic and anti-itch. Cortisone tablets may be indicated in severe cases.
Local anesthetics:
- Local anesthetics such as lidocaine have analgesic and antipruritic properties.
Acetic-tartaric clay solution:
- The acetic-tartaric clay solution is astringent (astringent) and cooling and is most often used as a gel in combination with chamomile and arnica.
Non-drug prevention
- Avoid known high-risk waters, especially shallow and marshy waters near the shore. Cercariae are most common in shallow waters near the beach. Prefer to swim in deep or flowing water and not early in the morning.
- After bathing, shower immediately and dry the body well with a towel. However, these measures can not prevent the development of the disease.
Medication prevention
For drug prevention, various repellents have been tested that are designed to prevent cercariae from entering the skin (Wulff et al., 2007). Effective agents included Safe Sea, a lotion used against jellyfish. External application of a niclosamide cream also appears to be effective for prevention. However, the antiparasitic niclosamide is not approved as a drug in many countries, and preparations must be made in pharmacies, for example, by incorporating niclosamide tablets from Germany (Yomesan) into a hydrophobic base. Yomesan is approved in Germany for the treatment of infestation with certain worms. We do not have sufficient data on possible risks to humans and the environment. Preparation of niclosamide cream 0.1% in a pharmacy:
| Yomesan chewable tablet (niclosamide 500 mg). | 1 piece |
| Hydrophobic base cream DAC | ad 500.0 |
Crush the chewable tablet in the ointment dish and mix with some foundation. Add the foundation in portions and homogenize (source: Pharmazeutische Zeitung).
