RESUMEN
INTRODUCTION: Paramphistomosis is a disease caused by the rumen flukes which cause an acute gastroenteritis and anemia with high mortality particularly in young ruminants. MATERIALS AND METHODS: In this study, we have investigated the anthelmintic effect of medicinal plant extracts from leaves and heartwoods of Cassia siamea L., roots of Plumbago zeylanica L. and Plumbago indica L., and leaves of Terminalia catappa L. against Carmyerius spatiosus. RESULTS: The highest anthelminthic effect on the flukes after 24 h of exposure was found in heartwood ethyl acetate extract of C. siamea (LC50 = 374.30; LC90 = 749.03 ppm), root n-butanol extract of P. zeylanica (LC50 = 1005.12; LC90 = 2411.55 ppm), root hexane, ethyl acetate, and n-butanol extract of P. indica (LC50 = 34.38, 211.34, 506.92; LC90 = 64.09, 496.05, 934.86 ppm), and leaf n-butanol and water extract of T. catappa (LC50 = 487.17, 470.28; LC90 = 913.27, 848.23 ppm). When observed by scanning electron microscopy, the tegument showed similar sequence of morphological changes after treatments with all plant extracts, comprising of swelling of ridges and folds, blebbing, rupturing of the blebs, erosion, lesion and disruption of the tegument. CONCLUSION: This study is the first report on the anthelmintic activity of plant extracts to C. spatiosus; therefore, these plant extracts are highly effective in the elimination of adult rumen flukes.