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The effects in vivo of 5, 10, and 20 mg/kg of luxabendazole (LBZ) on the tegument of Fasciola hepatica have been examined 48 h, 7 days and 14 days post-treatment of experimentally-infected rats. As early as 48 h post-treatment, the drug is shown to provoke significant damage to the tegument. The pathological phenomena characterizing LBZ damage are blebbing of the apical plasmalemma, formation of microvillus-like projections over the free surface, swelling of the basal infolds and stimulation of autophagy. The spines are often fractured; the tegument in the vicinity of spines seems more strongly altered than that in other foci. The basal layer is often changed, from increase of electron density to lack of integrity with the apical cytoplasm. The progress of the ultrastructural damage with time is not expressed. However, cytochemical data show that a longer post-treatment intervals the surface-coat structure becomes irregular and patches of ruthenium red positive material of variable thickness are focally accumulated. Only a slight dose-effect is noted 48 h after LBZ application when the alterations provoked by 5 mg/kg are less evident than those by 10 and 20 mg/kg.

The in vivo effects of the anthelmintics taenifugin, VUFB 14170 and VUFB 15269 on the tegument of Hymenolepis fraterna have been examined by SEM, TEM and cytochemistry. The drugs were given to H. fraterna-infected mice on the 14th day post-infection in a single oral dose of 150, 200 and 200 mg/kg, respectively. By 72 h post-treatment, the drug-induced pathomorphological changes in the tegument indicated that all three drugs had a significant effect. Changes were most pronounced on the brush border and in the intercellular material. On the apical surface, there was blebbing as well as accumulation of membrane fragments over the microthrix tips and erosion of the brush border. The intercellular material was changed in structure, showing increased electron density in some areas and oedema of the intercellular spaces in other areas. There were also fractures of the tegument of variable depth, sometimes reaching to the parenchyma. These results suggest altered tegumental integrity and, occasionally, complete disruption of the selective permeability barrier created by the normal tegument. This suggestion is further supported by the penetration of ruthenium red into some tegumental areas and its distribution into the intercellular spaces, down to the parenchyma. The intrategumental lysosomes also appeared to be significantly activated. There was evidence of autophagy in both distal cytoplasm and tegumental cells. Mature and gravid proglottides were more susceptible to drug damage than those in the anterior strobila and neck.