Fasciola hepatica: ultrastructural effects of a combination of triclabendazole and clorsulon against mature fluke.

A study has been carried out to investigate the ultrastructural effects of triclabendazole (TCBZ) at half-normal concentration, clorsulon at half-normal concentration, and a combination of these two drugs against mature Fasciola hepatica. The Cullompton TCBZ-susceptible isolate was used for these experiments. Flukes were incubated for 24 h in vitro in TCBZ sulphoxide (7.5 microg/ml), clorsulon (5 microg/ml), or a combination of the two drugs. For the in vivo experiment, rats were dosed with TCBZ (5 mg/kg body weight), clorsulon (5 mg/kg body weight), or a combination of the two drugs, and flukes recovered after 48 h. Fine structural changes within the tegumental syncytium and tegumental cells were assessed by transmission electron microscopy. Treatment with the combination of drugs produced greater disruption to the flukes than the individual drugs at half-normal concentrations, both in vivo and in vitro; also than TCBZ.SO at normal concentration in vitro. The changes observed aid in the understanding of the gross changes to the tegumental surface described previously (Meaney M, Allister J, McKinstry B, McLaughlin K, Brennan GP, Forbes AB, Fairweather I. Parasitol Res 99:609-621, 2006). The results indicate that there are additive effects between TCBZ and clorsulon and suggest that the use of drug combinations would be of value in the treatment of TCBZ-resistant fluke.