The anthelmintic potential of twelve solvent extracts of four plant species were studied against adult Fischoederius cobboldi using in vitro systems. Generally the ethyl acetate extracts of all the plants showed prominent activity by inhibiting the fluke’s motility and reducing their survival in a concentration dependent manner. Compared to the vehicle treated controls, a very significant (P<0.0001) mortality rate was observed for the Kaempferia rotunda ethyl acetate extract (25mg/ml) treated flukes within one hour of treatment. The alcohol extracts were also effective in inducing mortality with a prolonged treatment of two hours. Whereas the water extracts of all the four plants were least effective in killing these worms. Microscopy studies of these flukes revealed considerable morphological alterations to the surface syncytium, teguments, and suckers. Treatment of ethyl acetate and alcohol extract induced irregular lesions and severe degradation to the teguments. Alterations to the surface morphology were less with water extract treatment. The histological examinations revealed the loss of collagen in the cuticle as well as in the interior tissues of the trematode in these organic solvent extract treated animals. The qualitative screening of the extracts revealed the presence of flavonoids phenols and tannins with varying levels. Synergistic multi-targeted actions of these molecules are expected to contribute to the observed trematocidal activity of these plant extracts. The extract is therefore proposed for veterinary use after toxicity studies.

Keywords: Lagenandra. toxicaria, Kaempferia. rotunda, Desmodium. gangeticum, Tragia. involucrata, extracts, Fischoederius cobboldi, Paramphistomosis, trematocidal