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A 63-year-old woman developed a pruritic exanthema on the extremities after one hour of work in her garden pond in Planegg, Southern Bavaria. As the appropriate vectors (ducks and snails) were present, we made the tentative diagnosis of cercarial dermatitis (swimmer's itch). By different serological methods (cercarial fluorescent antibody test, cercarial Hüllen reaction, circumoval precipitin test) antibodies against cercariae could be demonstrated in the serum of the patient 14 days later. Cercarial dermatitis appears worldwide, but in Central Europe the disease is often not recognized.

Cercariae from trematodes of birds are capable of penetrating human skin causing a dermatitis, called swimmer's itch. In 1992, after a hot dry summer there was a marked increase in the incidence of cercarial dermatitis in Austria. Although the increased incidence of this complaint can be quite worrisome for the population, the occurrence of swimmer's itch can, in fact, generally be seen as harmless. Cercarial dermatitis responds well to treatment with topical antihistamines or cortisone; even without medication the skin rash heals within 2-3 weeks. The effectiveness of various preventive measures (such as protective sun cream or patting the skin dry) is controversial. The use of molluscicides is definitely contraindicated due to the inoffensive nature of this dermatitis. While it is usually easy to recognize swimmer's itch when there is an increased incidence, the diagnosis is often missed when it occurs sporadically, due to its unspecific characteristics.

Ocellate furcocercariae from the lymnaeid snail Radix auricularia have been identified as causative agents of swimmer's itch, which has become increasingly common in the 'Tunisee' near Freiburg. On an average 11.0%, maximally 25.0%, of the snails were parasitized with these trematode larvae. The Trichobilharzia parasitizing rate in the intermediate hosts found here was thus approximately 10-100 times higher than the Trichobilharzia prevalence described so far. Dwarf mallards (Anas platyrhynchos, blood red) were experimentally infected with Trichobilharzia cercariae from the 'Tunisee'. From the 13th day p.i. miracidia could be found in their faeces by means of the hatching method. The trematode eggs had the shape of an elongated spindle, with a pointed and a rounded end. The sexually differentiated adult worms were localized only in the hepatic and enteric veins. They had an average length of 4.0 mm (3.2-4.6 mm) and a width of 125 microns. Their tegument was strongly folded and had tegumental spines in the oral and ventral suckers, in males in addition along the canalis gynaecophorus. The most striking internal organ was the gut filled with hematin and separated in 2 caeca at its anterior end. Its form and localisation as well as those of the sexual organs were important criteria for the differentiation of the different Trichobilharzia species. The Trichobilharzia species found in the 'Tunisee' clearly differed from Trichobilharzia szidati both morphologically and physiologically. The latter has been considered, until now, to be the main causative agent of swimmer's itch in Germany. Moreover, the adult trematodes from the 'Tunisee' could not be associated with any other species of this genus. We propose therefore the name Trichobilharzia franki n. sp. for the species from the Tunisee.

During the pasture period in 1990 the snail species Helicella obvia, collected in a dicrocoeliosis area in the east of Brandenburg, was investigated for Dicrocoelium sporocysts. Simultaneously in adult snails the condition of albumen gland was examined. Investigations showed that Dicrocoelium infection in the snail host impairs their reproduction ability and life expectancy. The term "parasite caused sterilisation" is suggested for changes which lead to infertility in the case of parasite infection.

In the district of Frankfurt/Oder of the German Democratic Republic, faecal examinations of 143 sheep stocks revealed a 31.3 percent infection with Dicrocoelium dendriticum. In different territories of the district, the intensity of the infection with Dicrocoelium dendriticum varied remarkably. Detailed investigations demonstrated, that the parasite was limited to pastures with Brownearth soil. Routine examinations revealed the fact, that the egg-output of Dicrocoelium dendritcum was very variable during the pasture season. During the whole time of the examinations, the authors found eggs in the faeces of sheep belonging to Dicrocoelium dendriticun. In the German Democratic Republic, this helminth species is not restricted to hills with limestones. It occurs also in lowlands with small amounts of lime like the Brown-earth zones of the district Frankfurt/Oder.

Salmonellas of different serotypes and eggs of the helminths Ascaris lumbricoides L. and Trichuris trichiura L. were discovered in excrements, on the body surface and also on dead bodies on the gastropod Arion rufus L., which is partly coprophagous. Dipterans visiting such substrate may become--probably at most indirectly--vectors of these parasites and may be injurious to the health of men and domestic animals. By traps with carcasses of Arion as baits 178 species of Dipterans of 29 families were caught, among them species known as vectors and nearly all families in which species of vector function are stated. Investigation of foodstuffs and fodder revealed the occurrence of 144 of the 178 species of Dipterans stated on carcasses of Arion, mostly visitors on foodstuffs. Many of them may have vector function due to their chains of infestation. Informations are given on the spectrum of infection with salmonellae-serotypes and species of helminths stated on Arion and on the importance of Dipterans in the destruction of small carcasses. The results suggest the necessity of complementary investigations on the occurrence of further parasites on carcasses of gastropods.

A metacercarial infestation is reported in Canadian Umbra limi and a mass infestation by trematodes in Physa sp. from the same locality. Trials made by using parasitised snails showed that both parasites are not of the same species.

Ten lots, each one made up of 40 specimens of the snail Cernuella (Xeromagna) cespitum arigonis, were infected with L1 of the nematode Muellerius capillaris, at dosages ranging from 50 up to 1,000 L1/mollusc, in order to determine the influence of the infecting dose on the invasion and further development of the parasite population. Mathematical calculations are based on a basic model of a growing population. During the invasion phase a densith dependence on the number of available larvae was demonstrated, the process being adjusted to a binomial distribution and, secondly, to a Poisson type. The step from L1 to L2 was also density-dependent, and also the development from L2 to L3.

African Giant Snails (Achatina fulica) about 6 weeks old were experimentally infected with each 5,000 to 20,000 first stage larvae of Angiostrongylus vasorum or A. cantonensis by exposure to a larval suspension. The snails were histologically examined after various intervals after infection: 1 hour post infectionem (p.i.) larvae were present in the foot and 2 hours p.i. in addition in the gastrointestinal tract. 12 hours p.i. larvae were seen for the first time in the lung which reached nearly half of the total number of larvae via the hemolymph system. 24 hours p.i. or later 80-90% of the total larval population were detected in the foot and the lung. In the various organs (lung, mantle, hepatopancreas, gastro-intestinal tract, foot) the larvae were found in the loose connective tissue near or within the hemolymph vessels. The cellular defense mechanism of the snail is activated 12 hours p.i. and the parasites are surrounded by large numbers of leucocytes (leucocytic encapsulation). Three days p.i. the nuclei of the cells become spindle shaped and are forming concentric layers in the outer part of the capsule (fibroblastic type of encapsulation). Later on the wall of the encapsulation becomes thinner and a karyolysis can be recognized in the centre, consequently a cavity occurs. Encapsulations in organs poor in muscle cells can histologically not be differentiated from those located in the foot, which consists mainly of muscle cells; a myofibrous type of encapsulation has to be doubted. The effects of the infection on the snail are discussed.

In this study, carried out in the Ivory Coast, Dicrocoelium hospes Looss, 1907 was shown for the first time to be a parasite of cattle and it was also detected in sheep by the presence of ova in the faeces. Up to 50% of the sheep in some flocks were found to shed eggs. The adults, sporocysts, "slime balls" and cercariae of D. hospes are described and compared to the respective stages of D. dendriticum. This comparison shows that essential morphological structures are very similar, especially the sensory papillae, which as so called chaetotaxis can serve to distinguish closely related species. The cercariae develop in terrestrial snails of the genus Limicolaria of which several species may play a role (L. flammea, L. felina, L. kambeul). The main habitat of D. hospes seems to be limited to savannah environment; only once could D. hospes be found in the borderzone between savannah and the rain forest. Infected Limicolaria-snails shed the cercariae in amorphous "slime balls" of liquid-jelly-like consistency and yellowish colour. Under the influence of sunlight these liquify; the cercariae, however, can survive for up to 26 h. According to our present knowledge the sunlight seems to be a factor which triggers the shedding of slime balls. This begins shortly after sunrise at a temperature of 22 degrees C and a relative humidity of 100%. Infected snails can shed cercariae on seven consecutive days. This kind of slime ball production might provide a clue to the 2nd intermediate host; efforts to identify this host have, however, so far been fruitless, despite the fact that almost 4000 arthropods, mainly ants, have been investigated.

Pilot trials are described in which BHS, a Czechoslovak fasciolicide, was employed for mass treatment of fasciolosis in cloven-hoofed animals in wild-animals' reserves at the rate of 30 mg body weight using BHS-medicated feed. The treatment was combined with control measures against the intermediate host snail, Lymnaea truncatula, in primary biotopes using Frescon, a molluscicide of English origin, and CF-4, a molluscicide of Czechoslovak origin, at concentration of 1 and 0.5 per cent, respectively. Where the application of molluscicides was impracticable the intermediate host snails were controlled by means of sciomyzid larvae or by blasting surface layers of the soil.--Using this combined approach, the extensity of infestation, evaluated on the basis of coproovoscopical examination, was reduced from 7.05 to 0.71 per cent. The extensity of infestation, evaluated on the basis of necropsy findings, was reduced from 50 to 6.2 per cent. The intensity of infestation was reduced from 7.7 to 0.31 per cent per animal.--The results may prove useful in devising fasciolosis control schemes based on a complex approach.

Swimmer's dermatitides occurring in natural--accordingly polluted--waters are most probably of chemical nature. In clean waters, however, they are primarily caused by larvae of duck-flukes, the so called cercariae. In a natural pool near Biberach undetermined cases of swimmers' dermatitis have appeared. Hence a cercarial dermatitis was suspected and specific examinations were carried out. At the biological examination of the pool, many watersnails of the species Radix ovata have been found near the shore. Out of 180 collected snails 8 produced cercariae of different trematode species. Hence an infective cycle between duck and snail could be ascertained here. However, the special cercariae, producing dermatitis, could not be found. Having taken that into account the author was standing in the snail biotop without protective clothes for about 1 hour to provoke cercarial dermatitis. A few minutes later the corresponding clinical picture with an extremely strong itching developed. Papules were to be seen 12 h later, the symptoms lasted 2 weeks altogether. By different serological methods (Cercarienhuellenreaction) indirect immunofluorescent test with complete cercariae and cercarial sections antibodies against cercariae could be demonstrated in the serum of the author 14 days later. As a therapy only the symptomatic treatment of the itching is possible. In principle etiologic measures against cercarial dermatitides are possible by chemical snail control. But as a rule this is to be refused because of the severe ecological damages. However, in case of swimmers' dermatitis it is nonetheless indispensible to clarify eventual parasitogenic reasons because of the specific hygienic consequences.

Epizootiological questions were studied on a permanent pasture of a farm situated in one of the dicrocoeliasis areas in the GDR during the 1986 grazing season. Helicella obvia snails and Formica fusca ants were found to be first and second intermediate hosts respectively. A total of 1,121 snails and 70 ants were dissected. The infestation rate with Dicrocoelium dendriticum stages in snails decreased in summer after the high spring peak and increased again in autumn. Paralysed ants were found only at temperatures below 20 degrees C. Parthenogenetic stages in snails were identified morphologically according to the structure of cercariae; the metacercariae isolated from the ants' body cavity were determined in animal experiments.