Abstract: In order to study the effect of Melia azedarach on Haemonchus contortus,this experiment was to observe the effect of Melia azedarach extract on the activity and morphological changes of eggs and larvae,and to evaluate its repellent activity on Haemonchus contortus,so as to lay a foundation for the prevention and control of Haemonchus contortus disease in domestic animals and the research and development of plant repellents.In the experiment,5 concentrations (25,12.5,6.25,3.125 and 1.562 mg/mL) of water extract and ethanol extract of Melia azedarach were set for egg hatching test and larva activity test.The eggs and larva treated with different concentrations of drugs were counted,and the hatching state and morphological change of eggs and larva were observed after the action of drugs.The results showed that the activity of the eggs and larvae was good.48 h after the action of Melia azedarach extract,the eggs were in the state of non hatching and half hatching,and developed to the stage of mulberry,tadpole and larval death.The water extract and alcohol extract of Melia azedarach at different concentrations inhibited the hatching of the eggs,and the inhibitory effect of alcohol extract of Meliae on the hatching of the eggs was the best.At the concentration of 25 mg/mL,the alcohol extract of Meliae inhibited the hatching of the eggs,and the inhibition rate of hatching was 98.2%.At 12.5 mg/mL,the inhibitory rate of wormwood extract on worm eggs was significantly higher than that of oxydermal extract (P<0.01).The lethal effect of Melia azedarach seed extract on infective third stage larvae was poor,only at 50 mg/mL,it had a higher lethal rate to larvae,and the mortality rate was 82.6%.When the concentration of water extract of Meliae was 50 mg/mL,its lethal effect on larva was particularly prominent,the mortality rate of larva was 97.0%,and the dead larva was "linear" or "bow".By variance analysis,in the range of 12.5 to 50 mg/mL,there was a significant or extremely significant difference in the lethality rate between the water extracts of Melia azedarach at the same concentration (P<0.05;P<0.01).There were extremely significant differences in lethal rate of larva between the alcohol extract at the same concentration (P<0.01).In conclusion,Melia azedarach extract could inhibit the activity of eggs and infective third stage larvae of Haemonchus twist in vitro.Among them,25 mg/mL Meliae alcohol extract had the best inhibitory effect on egg hatching,and 50 mg/mL Meliae water extract had the best lethal effect on infective third stage larvae.

Key words: Melia azedarach; extract; Haemonchus contortus; activity