[A contribution to the biology of Dicrocoelium hospes Looss, 1907 (Trematoda, Dicrocoeliidae)].

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.