In Vitro Larvicidal Activity of Hydroalcoholic Extracts from Four Pleurotus djamor Fungal Strains Against Haemonchus contortus

The aim of this study was to assess the in vitro larvicidal activity of hydroalcoholic extracts (HAE) from four Pleurotus djamor fungal strains against Haemonchus contortus infective larvae (L3) and to evaluate the associated structural alterations in the larval cuticle using scanning electron microscopy (SEM) as an alternative to chemical anthelmintics. HAE were obtained from fruiting bodies through maceration. Larvae/HAE confrontation was carried out in 96 well ELISA plates. Two similar experiments were simultaneously performed to assess the HAE activity against sheathed (ShL3) and exsheathed (ExshL3) H. contortus larvae, respectively. Six well series ( n = 4) were confirmed in every assessment. Each well contained 200 H. contortus (L3) in 20 μL of distilled water plus the corresponding HAE as follows: Series 1) Negative control (Distilled water 80 μL); Series 2) Positive control (Ivermectin 10 mg/mL); Series 3) P. djamor ECS-0142 strain (Pd-ECS-0142); Series 4) P. djamor ECS-0143 strain (Pd-ECS-0143); Series 5) P. djamor ECS-0127 strain (Pd-ECS-0127); Series 6) P. djamor ECS-0123 strain (Pd-ECS-0123). The different fungal HAE were assessed at the following concentrations: 20, 40, 80, and 175 mg/mL. Proportions of recovered larvae and larval mortality percentage were estimated, and the medium lethal concentration (LC 50 ) was also estimated. Pd-ECS-0127, Pd-ECS-0142, and Pd-ECS-0143 HAE showed mortality percentages lower than 50%. In contrast, Pd-ECS-0123 HAE showed an in vitro larvicidal activity ranging between 90 and 100% against both ShL3 and ExshL3 H. contortus (L3) after 72 h post-confrontation. LC 50 values of the fungal HAE with ShL3 and ExshL3 showed variability ranging from 71.30 to 167.5 mg/mL. The exposure of larvae to the Pd-ECS-0123 HAE at 175 mg/mL produced changes in the normal structural integrity of larvae.