Evaluation of the Efficacy of Anthelmintic Drugs Against Trichinella spiralis Larvae

<b>Background</b>: Albendazole, mebendazole, and ivermectin are effective against adult <i>Trichinella spiralis</i> but show limited efficacy against encapsulated muscle stage larvae. This limitation highlights the need for improved experimental approaches to evaluate anthelmintic activity at this stage and to identify alternative therapeutic candidates. <b>Methods</b>: Seven antiparasitic drugs, albendazole (ABZ), miltefosine (MLT), ivermectin (IVM), tribendimidine (TBD), praziquantel (PZQ), artesunate (ART), and mefloquine (MEQ), were evaluated for in vitro activity against <i>T. spiralis</i> muscle larvae. Larval viability was quantified using a tetrazolium salt XTT assay to determine IC₅₀ values and compare with microscopic assessments. Based on in vitro activity, TBD was selected for in vivo evaluation in a mouse model, where efficacy was assessed by muscle larval burden and histopathological changes. <b>Results</b>: TBD, MEQ, IVM, and ABZ exhibited measurable in vitro efficacies against <i>T. spiralis</i> larvae, with TBD showing the lowest IC₅₀ value at 135.2 μM. XTT formazan absorbance correlated strongly with larval number and incubation time. In vivo, TBD treatment significantly reduced larval burdens in diaphragm and gastrocnemius muscles and was associated with reduced collagen capsule thickness, inflammation, and fibrosis compared with ABZ-treated controls. <b>Conclusions</b>: This study validated an assay for quantitative evaluation of <i>T. spiralis</i> muscle larvae and demonstrates robust in vitro and in vivo activity of TBD against this stage.