DIFFICULTIES IN DIAGNOSING CERCARIOSIS USING A CLINICAL CASE EXAMPLE

Abstract

Doctors of various specialties, both general and specialized, may face difficulties in diagnosis, including overdiagnosis, and treatment of schistosomal dermatitis, or cercariosis. Differential diagnosis and the formulation of this diagnosis may be difficult due to the masking of clinical manifestations for allergic diseases or dermatitis of other etiologies.  Cercariasis is a parasitic human disease that is caused by larvae (cercariae) of the family Shistosomatidae. Adults live in the digestive system of waterfowl (most often ducks). The intermediate host is freshwater mollusks, which live in the warm water of the coastal zones of stagnant reservoirs. Cercaria larvae with a size of less than 1 mm come out of the mollusks into the water. They penetrate the skin of birds, reach the digestive system through blood vessels, and the life cycle of the parasites repeats.  Human skin in this cycle may turn out to be an accidental target of damage to cercariae larvae. In this case, humans are a biological dead end for parasites. However, penetrating into the skin, the larvae cause a toxic-allergic reaction – maculopapular rash ("bathers' itch", "water itch", schistosomatid dermatitis), after which, after 3-6 weeks, under the action of protective mechanisms of local human immunity, the cercariae die.

Case description. In the presented clinical case, cercarial dermatitis in a 4-year–old child is described in the form of spotty papular itchy rashes on the skin of the forearms and thighs - places of contact with fresh water when bathing a child in the coastal area of a city lake with wild ducks. The differential diagnosis was performed with atopic and contact dermatitis, allergic reactions. At the same time, there were no abnormalities in the somatic status and laboratory tests (general analysis of blood, urine, feces, including helminths). The diagnosis is based on the clinical picture and epidemiological history: the appearance of a rash a few hours after contact with warm, standing water; no changes in the somatic status and in general tests; resistance to antihistamines and corticosteroids; self-healing in the second week after the onset of the disease.

Conclusion. The described case is of interest to general practitioners and specialized specialists, as it requires not only differential diagnosis with dermatoses of a different etiology, but also as an occasion for conducting social and educational conversations with parents about the danger of infection with cercariasis when swimming in reservoirs with waterfowl.