What is Schistosomatid Dermatitis?
Schistosomatid dermatitis (dermatitis schistosomatida, itching bathers (swimmers), water itching, cercaria dermatitis, water nettle, rotten sludge) – a parasitic disease characterized by skin lesions that occurs after bathing, due to the penetration of schistosomatids into the skin of cercaria.
The disease, except for a number of tropical countries in Africa, Asia, Australia, occurs, although much less frequently, in some countries of the temperate zone, in particular in the USA (especially in the region of Lake Michigan), Canada, France, Italy, etc.
In Russia, isolated cases of schistosomatid dermatitis were described by R. S. Chebotarev (1957) in the floodplain of the Dnieper, Yu. V. Kurochkin (1959) in the Volga Delta, P.P. Popov (1963) in the Azerbaijan SSR, V.I. Zdun ( 1964) in the Ukrainian SSR.
Causes of Schistosomatid Dermatitis
The causative agents of schistosomatid dermatitis are helminth cercariae, which, at the stage of puberty, parasitize in the blood vessels of waterfowl (ducks, gulls, swans, etc.). Sometimes dermatitis can be caused by cercaria schistosomatids of mammalian animals (rodents), as well as schistosomatids S. haematobium, S. mansoni, S. intercalatum, S. japonicum.
Currently, there are more than 20 schistosomatids, cercariae of which are able to penetrate the human skin. Most of them die in the skin. In most cases, schistosomatid dermatitis is caused by the cercaria Trichobilharcia ocellata and Trichobilharcia stagnicolae. Trichobilgaria eggs fall into the water with feces, embryos hatch from them – miracidia, penetrating into mollusks, where they turn into cercariae, which, once in water, are introduced into the body of ducks through their skin. After 2 weeks in the circulatory system, they reach puberty.
Pathogenesis during Schistosomatid Dermatitis
Human disease usually occurs when bathing or working in ponds, swampy, standing or slowly flowing water bodies contaminated with feces of infected birds, mammals or humans. At the same time, the direct cause of the disease is the penetration into the skin of cercariae released from mollusks. There is an indication [Chu, 1952] that, for example, infection in the Hawaiian Islands is possible even when swimming even in the sea. A. J. Bearup and W. A. Langsford in 1966 described multiple schistosomatid dermatitis in Australian residents cultivating rice.
Whatever the contact with the cercariae, they, having attached themselves to the skin of a person, quite quickly with the help of a special biting device located on their head end, are embedded in the thickness of the skin. Further migration of cercariae in the skin is facilitated by the still lysing effect of the secrets of penetration glands secreted by them.
In pathogenesis, toxic-allergic reactions due to the products of the metabolism and decomposition of helminths, the mechanical action of parasites and the release of lysing secrets into the tissues by the glands during the penetration of parasites are of leading importance. In the epidermis, edema with lysis of epidermal cells develops around the places where cercariae are introduced. As cercariae migrate in the corium, leukocyte and lymphocyte infiltrates occur. As a result of the developed immunological reaction, schistosomatids die in human skin and their further development stops.
Symptoms of Schistosomatide Dermatitis
Itchy skin appears 10-15 minutes after the penetration of cercariae into the skin, and an hour after bathing a spotted rash appears on the skin, disappearing after 6-10 hours.
With repeated infection, dermatitis is more acute, with severe skin itching and the formation of erythema and red papules on the skin. Papules appear on the 2nd-5th, and sometimes on the 5th-12th day. They can hold for 15 days. Occasionally, swelling of the skin and blisters occur. The disease ends in 1-2 weeks.
Diagnosis of Schistosomatid Dermatitis
Diagnosis is based on epidemiological history and clinical manifestations of the disease.
Treatment of Schistosomatide Dermatitis
To reduce itching, ointments containing a 5% solution of diphenhydramine or ditrazine are used. In addition, diphenhydramine is administered orally at 0.05 g 2-3 times a day. In severe cases, the use of prednisone or ACTH is indicated.
The forecast is favorable.
Prevention of Schistosomatide Dermatitis
Before bathing, you can lubricate the skin with an ointment containing 40% dimethyl phthalate or dibutyl phthalate.