The use of plants for the treatment of human and animal diseases continues to rise although there are few studies providing proof of these effects. Among them is the Anacardium occidentale L., popularly known as cashew. In vitro egg hatch and larval development and viability assays was conducted to determine possible direct anthelmintic effect of acetone extract and fractions of A. occidentale against nematode of sheep, predominantly, Haemonchus contortus. The effect of the extracts on hatching

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... of eggs and development and survival of infective larvae (L 3 ) was assessed. The best-fit LC 50 values were computed by global model of non-linear regression curve fitting (95% confidence interval). The presence of A. occidentale extracts in the cultures decreased the hatchability of eggs and survival of L 3 larvae in a concentration dependent manner. The LC 50 values of acetone extract was 0.311 and 1.72 mg/ml for egg hatch and larval viability test, respectively. The fractions of A. occidentale were more active, demonstrating a lower LC 50 compare with the acetone extract. The activities of the fractions were not significantly different against the eggs and larvae of H. contortus (p > 0.05). Further studies are required to identify the compound(s) responsible for activity and more clearly comprehend the anthelmintic mechanism detected in this study.