Investigations of intermediate host specificity help to elucidate the taxonomic status of Trichobilharzia ocellata (Digenea: Schistosomatidae).

The avian schistosomatid Trichobilharzia ocellata plays an important role as causative agent of cercarial dermatitis of humans in Europe. In order to improve the taxonomic knowledge on this parasite, studies of miracidial chemo-orientation as well as experimental infections of different snail species were conducted using strains of T. ocellata and T. franki. Both schistosomes exhibited a high intermediate host specificity. The miracidia clearly preferred the SCW (snail-conditioned water) of the respective natural intermediate host to SCW of other sympatric snail species. T. ocellata proved to be capable of infecting Lymnaea stagnalis and Stagnicola palustris, but could not develop in Radix ovata or R. auricularia. T. franki established an infection in specimens of R. auricularia and R. ovata, but not in L. stagnalis or S. palustris. The results imply that the intermediate host spectrum of T. ocellata is limited to L. stagnalis and S. palustris. Findings of T. ocellata (or Cercaria ocellata) that originated from snails of the genus Radix are likely to have actually belonged to species such as T. franki or T. regenti. The assumption that T. szidati is synonymous to T. ocellata is also discussed.