There are numerous cases of dermatitis described world-wide and resulting from the influence of the furcocercaria of the bird schistosome. The host snail species of the schistosome, producing thousands of furcocercaria are common in our country. But, because of too general symptoms of dermatitis resulting from the influence of the schistosome of the larvae, there are many unrecognisable cases. The reaction described was typical of a twenty-seven-year-old man collecting snails in the Piechota Bay in Gostynin (the Province of Kuyavia and Pomerania). In that reservoir, individuals of Lymnaea stagnalis were found, which were infected with sporocysts and furcocercaria of Trichobilharzia ocellata. In the laboratory conditions, a high expulsion of cercaria was observed, which amounted to over 8000 larvae per snail.
Biomphalaria pfeifferi (Krauss) and Bulinus truncatus (Audouin) were infected with schistosome parasites. Infected B. pfeifferi occurred in 5 (11.9%) while infected B. truncatus occurred in 2(4.8%) of the 42 sites surveyed. Snail infection was highest (6.2%) from May to July and lowest (3.0%) from February to April. The number of infected snails increased with density. The snail population peaked in June while the smallest number were collected in March. The seasonality of the snail population was attributed to changes in the rainfall pattern.