The chemotherapy of monogeneans which parasitize fish: a review.

Monogeneans which parasitize fish are still treated by bathing the fish in solutions of simple chemicals or staining dyes. In the early 1960s an insecticide, trichlorphon, replaced to a large extent the formerly used simple chemicals. Its success was greater specificity against monogeneans and other ectoparasites, and to its great tolerance by the fish. The fact that the number of important monogenean species (i.e. Pseudodactylogyrus anguillae, P. bini, Gyrodactylus salaris) which cannot be treated sufficiently with simple chemicals or even trichlorphon is increasing, led to the need for systemically acting, novel chemotherapeutics. In laboratory and small scale trials praziquantel, levamisole, mebendazole and toltrazuril have been tested for efficacy against a broad spectrum of monogenean species.