Beauveria bassiana is a potential effective biological agent against Psoroptes ovis var. cuniculi mites

Beauveria bassiana is an entomopathogenic fungus known for its high efficacy against many agricultural insect pests, and is considered to be safe to the environment. Previous studies showed that B. bassiana is also capable of infection and horizontal transmission between Psoroptes ovis mites, but we still lack information on the clinical efficacy of B. bassiana against P. ovis. In this study, we evaluated the acaricidal efficacy of B. bassiana against Psoroptes ovis var. cuniculi, both in vitro and in vivo. Tests consistently showed that B. bassiana caused high mortality against P. ovis var. cuniculi in vitro with dose- and time-dependent susceptibility responses; applying 4.26 x 10(9) conidia/ml resulted in 100% mortality of P. ovis var. cuniculi within 9 days with an LT50 of 2.50. In vivo, rabbits infected with P. ovis var. cuniculi that were treated with 4.26 x 10(9) conidia/ml B. bassiana fungal suspension showed a 100% therapeutic response 3 days later, an efficacy greater than that of the anti-parasitic drug ivermectin. Moreover, no rabbits treated with B. bassiana showed symptoms of disease recurrence by 60 days post-treatment. Taken together, these results show that B. bassiana has high efficacy against P. ovis var. cuniculi; hence, it may be a potentially effective biological insecticide for use against psoroptic mange.