Eugenol; Effective Anthelmintic Compound against Foodborne Parasite Trichinella spiralis Muscle Larvae and Adult

Trichinosis is a foodborne parasitic infection that results from ingestion of raw or under-cooked pork meat infected by parasitic nematode Trichinella spiralis with cosmopolitan distribution. Anthelmintic drugs are used to eliminate intestinal adult parasites and larvae as well as tissue-migrating newborn and in-turn encysted larvae. However, eliminating the infection or averting it from transmission is rarely possible using anthelmintic groups of benzimidazole derivatives. Eugenol (EO) is the main extracted constituent of clove oil (80−90%) and is responsible for its aroma. Therefore, this study aims to investigate the effect of eugenol on both adult and muscle larvae of Trichinella spiralis in vitro. IC50 for different concentrations of eugenol were calculated for both muscle larvae (187.5 µM) and adults (190.4 µM) to determine the accurate dose range. Both the nematode stages were cultured in the commonly used RPMI-1640 media in 24-well plates. Different concentrations of eugenol (122, 305, 609, 1218, and 3045 µM) were administered in different groups of larvae/adults. The parasitological parameters were monitored after 1, 3, 6, 10, 24 h for each EO concentration in concomitant with the control groups. Reference chemotherapeutic anthelminthic drug “albendazole” (at dose 377 µM) was experimentally grouped in triplicates as positive control and the untreated as negative control, respectively. Mortality was observed where time-dependent adult stages were less susceptible than muscle larvae. Eugenol achieved 100% efficacy against T. spiralis larvae and killed the total larvae after 10 and 24 h at concentrations of 1218 and 3045 µM, the same as albendazole’s effect on the positive control group. In regard to adults, resembling muscle larvae (ML), a significant effect of both concentrations at p < 0.0001 was obtained, and the concentration × time interaction was significant at p < 0.0001. Furthermore, the treated/untreated adult and muscle larvae were collected and processed for scanning electron microscopy (SEM). Massive destruction of parasite burden was observed, especially at high concentrations (1218 and 3045 µM). In addition, complete and mild loss in cuticular striation in both the treated and positive controls were confirmed by SEM, respectively, in comparison to the control untreated group.