Objective Ticks serve as vectors for transmitting Babesia microti.However,the specific mechanism remains unclear.This study aimed to investigate the effect of tick autophagy molecules on the proliferation of Babesia microti.Methods An experimental model of infected and uninfected mice was used to collect tick materials for proteomic analysis to identify differentially expressed autophagy-related molecules in Haemaphysalis longicornis.The cloning of the HlATG8 gene,protein expression,and production of polyclonal antibodies were completed.The HlATG8 gene was then knocked down using RNAi interference technology.Results The tick autophagy molecule,HlATG8,was identified and found to be significantly upregulated in ticks infected with Babesia microti.The load of Babesia microti in ticks increased significantly following the knockdown of the HlATG8 gene.Conclusions The tick autophagy molecule in Hae.longicornis,HlATG8,inhibits the proliferation of Babesia.