A Preliminary Study On The Pathogenicity And Pathogenic Mechanism Of Metarhizium Anislpliae Against Psoroptes Ovis Var.cuniculi

The Psoroptes ovis mite is a common ectoparasite,with infection rate of 11.11%~ 70.00% in China’s rabbit breeding industry.Psoroptic mange was caused by Psoroptes ovis var.cuniculi with scab formed in the external auditory canal of rabbits,and caused weight reduction,reducing meat quality,and sometimes resulting in death.Thus,this disease address huge economic losses and hinder the development of rabbit.Importantly,multiple acaricides were reported recently resistance to cause treatment failures.As people’s demand for green foods increases,new,green,and effective methods for preventing and controlling P.ovis need to be sought.Metarhizium anisopliae,an entomopathogenic fungus,is well known as an effective fungal biocontrol agent to control pests in agriculture and forestry,and previous studies proved that M.anisopliae showed a high level of pathogenicity to P.ovis in vitro,but it is unclear whether it has a clinical therapeutic effect aganist P.ovis var.cuniculi,and its pathogenic mechanism aganist P.ovis var.cuniculi is not yet clear.We investigated the potential activity against P.ovis var.cuniculi in vitro and in vivo,and further explored its pathogenic mechanism.The main results are as follows: 1 The pathogenicity of M.anisopliae to P.ovis var.cuniculiIn order to study whether M.anisopliae is pathogenic aganist P.ovis var.cuniculi.We investigated the potential activity of M.anisopliae(1010,109,108,and 107 spores/m L)against Psoroptes ovis var.cuniculi in vitro.The rabbit acariasis patients were sprayed with the best killing concentration selected in the ex vivo test,while the ivermectin subcutaneous injection group and the sterile water spray group were used as positive and negative controls.The clinic efficacy of M.anisopliae was evaluated across the experimental period.M.anisopliae showed a high acaricidal activity against P.ovis var.cuniculi in both a time-and dose-dependent manner in vitro.At the 109,1010 spore/ml concentration,M.anisopliae killed 93.33% and 100.00% of the mites in 9 days,respectively.Notably,M.anisopliae treatment showed a higher therapeutic effects,all rabbits were clinically cured and recovered completely at day 21 post-treatment.The therapeutic effect was comparable to that of the ivermectin group.The results showed that M.anisopliae showed a high level of pathogenicity to P.ovis in vitro and in vivo.2.A Preliminary investigation on the insecticidal mechanism of Metarhizium anisopliae against Psoroptes ovis var.cuniculiIn order to investigate the insecticidal mechanism of M.anisopliae against P.ovis var.cuniculi,the m RNA transcription and enzymatic activity of glutathione-s-transferase(GSTs),superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)were tested after the treatment with M.anisopliae(109 spores/ml)from 1~7 days.The results showed that the GSTs,SOD,CAT m RNA transcription levels and protein levels of the M.anisopliae group generally showed a trend of increasing first and then decreasing,but the overall change of POD in the M.anisopliae group had little difference with the control group.The results indicate that the M.anisopliae may have a toxic effect on P.ovis var.cuniculi and activate detoxification enzymes and protective enzyme in the mites,which enabled the four enzymes to detoxify and protect the mites.Furthermore GSTs and SOD played a greater role in the protection of parasites,and POD and CAT played a minor protective role.