Evaluation of the Anthelmintic Potential of Aqueous and Ethanolic Leaf Extracts of Vitex negundo against Benzimidazole-resistant Haemonchus Contortus in 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
Background: Vitex negundo is a large aromatic shrub, sometimes a small slender tree, found throughout the greater parts of India. Traditionally, leaves are reported to possess a tranquillising effect, insecticidal properties, and are laid over grain to ward off insects.
Study Aim: 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.
Method: The organised sheep farms in the various districts of Tamil Nadu, viz., Thiruvallur, Kancheepuram, Salem, Karur and Kanniyakumari were randomly selected for sampling. In this study, 560 faecal samples were collected from organised sheep farms from the above districts before and after deworming with benzimidazole (BZ). The BZ-resistance was tested in this study by in vivo tests, viz., faecal egg count reduction test (FECRT) and allele-specific polymerase chain reaction (AS-PCR) and in vitro tests, viz., egg hatch assay (EHA) and larval paralysis assay (LPA).
Results: 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.
Conclusion: 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. Future studies should focus on further investigations of Vitex negundo to evaluate its potential in combating anthelmintic resistance in farm animals.
Keywords: Nematodes, Haemonchus contortus, Vitex negundo, benzimidazole, anthelmintic resistance