In vitro Evaluation of Anthelmintic Potential of Aqueous and Ethanolic Leaf Extracts of Vitex negundo in Benzimidazole-resistant Haemonchus contortus of Sheep
R. Edith *
Department of Veterinary Parasitology, Veterinary College and Research Institute, Salem-636 112, Tamil Nadu Veterinary and Animal Sciences University, India.
M. Balagangatharathilagar
Department of Clinics, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai-600 007, India.
*Author to whom correspondence should be addressed.
Abstract
The aim of this study was to evaluate the aqueous and ethanolic leaf extracts of Vitex negundo for their anthelmintic potential against the benzimidazole-resistant Haemonchus contortus of sheep. The organized sheep farms in the various districts of Tamil Nadu viz., Thiruvallur, Kancheepuram, Salem, Karur and Kanniyakumari were randomly selected for sampling. 560 faecal samples were collected from organized sheep farms from the above districts before and after deworming with benzimidazole (BZ). The faecal egg count reduction test (FECRT) revealed the development of anthelmintic resistance to BZ in Thiruvallur and Kancheepuram districts. The allele-specific polymerase chain reaction (AS-PCR), the molecular technique employed to amplify the 250bp BZ-resistant gene fragments, had also revealed the BZ resistance. This study evaluated the anthelmintic potential of Vitex negundo leaves against BZ-resistant H. contortus in sheep. The aqueous leaf extracts (ALE) and ethanolic leaf extracts (ELE) of V. negundo were prepared in various concentrations, viz., 5, 10, 20, and 50 mg/mL. The in vitro methods viz., egg hatch assay (EHA) and larval paralysis assay (LPA) were performed to assess the anthelmintic efficacy of the above extracts. EHA revealed maximum efficacy (%) of 11.67±1.67% and 5.00±0.91% in 50 mg/mL concentration of ALE and ELE, respectively. LPA revealed 13.44±1.41% and 7.23±0.55% efficacy in 50 mg/mL concentrations of ALE and ELE, respectively. The results of this study with V. negundo indicated a dose-dependent effect of ALE and ELE in EHA and LPA. It is concluded that V. negundo could be a futuristic phytomedicine for an alternate control strategy to combat the anthelmintic resistance against BZ-resistant strongyle nematodes of sheep.
Keywords: Nematodes, Haemonchus contortus, Vitex negundo, benzimidazole, anthelmintic resistance