Fasciola hepatica: Motility response to fasciolicides in vitro

Abstract

The effects of a wide range of fasciolicides on the in vitro motility of Fasciola hepatica have been determined by means of an isometric transducer system. Carbon tetrachloride and diamphenethide do not affect movement at concentrations up to 500 and 100 μg/ml, respectively; at 1000 μg/ml, however, carbon tetrachloride induces a rapid tonic paralysis. Brotianide and the deacetylated metabolite of diamphenethide cause a rapid flaccid paralysis of the fluke at concentrations of 1.0 μg/ml and above. In contrast, the effect of MK-401 is a long-term one, a flaccid paralysis occurring after 20 hr only at 200 μg/ml. Praziquantel also produces a flaccid paralysis of the fluke, but this follows an initial increase, then decrease, in muscle tone. The effect is rapid at 500 μg/ml, but long-term at 100 and 200 μg/ml; at these lower concentrations there is also a stimulation of activity. Oxyclozanide, rafoxanide, niclofolan, bithionol, and hexacholorophene induce a rapid spastic paralysis of the fluke at concentrations of 1.0 μg/ml and above. Both phasic and tonic components are evident in the response at concentrations of 1.0 μg/ml and below; the phasic component disappears at higher concentrations. Nitroxynil produces a similar effect, evident at higher concentrations. Among the benzimidazoles, mebendazole, oxfendazole, and albendazole sulphoxide cause a suppression of motility, whilst thiabendazole and albendazole produce a stimulation of movement. The effects are not rapid, however, for only mebendazole at 500 μg/ml causes total inactivity of the fluke within a 12-hr period. Possible explanations for these effects on fluke motility are discussed. © 1984.