Human cystic echinococcosis remains a major public health problem on several countries and the treatment strategies are not solved. The aim of the present work was to determine the in vitro effect of thymol andMentha piperita,M. pulegium,andRosmarinus officinalisessential oils on the proliferation ofE. granulosuslarval cells. Isolated cells and cellular aggregates were obtained from hydatid cyst’s germinal layer and exposed to 1, 5, and 10 μg/ml of thymol and the different essential oils for 7 days. Drug effect was evaluated using test viability and scanning electron microscopy. Control cell culture viability was 2.1 x 10⁶(100%) after 7 days of incubation. At day 7, thymol 5 μg/ml caused a reduction in cell viability of 63% and the essential oils ofM. piperita10 μg/ml,M. pulegium10 μg/ml, andR. officinalis10 μg/ml produced a reduction in the viability of 77, 82, and 71%, respectively. Moreover essential oils caused reduction in cell number, collapsed cells, and loss of normal tridimensional composition of the aggregates. Due to the inhibitory effect caused by essential oils onE. granulosuscells we suggested that it would be an effective means for suppression of larval growth.

Cystic echinococcosis is a zoonotic disease caused by the parasite Echinococcus granulosus sensu lato (s.l.), which is worldwide distributed and causes long-lasting infections in animals and humans. The existing treatment is limited to the use of benzimidazoles, mainly albendazole (ABZ). However, it has unwanted side effects and its efficacy is about 50. The Asteraceae family includes plants that have therapeutic applications (medicinal species) and has an important role in new drug development. The species belonging to a different genus of this family show a wide range of anti-inflammatory, antimicrobial, antioxidant, hepatoprotective, and antiparasitic activities, among others. The aim of the present study was to evaluate the in vitro efficacy of extracts of four Asteraceae species against protoscoleces of E. granulosus sensu stricto (s.s.). On the other hand, the Stevia aristata extract was assessed on the murine cyst of E. granulosus (s.s.) and the efficacy of S. aristata extract was investigated in a murine model of CE. Stevia satureiifolia, S. aristata, Grindelia pulchella, and G. chiloensis extracts at 100μg/mL caused a decrease in protoscoleces viability; however, S. aristata extract produced the greatest in vitro protoscolicidal effect. After 20 days of treatment with the highest concentration (100μg/mL) of S. aristata extract, protoscoleces viability decreased to 0. The tegumental changes observed by scanning electron microscopy were consistent with the reduction in vitality. The collapse of the germinal layer was registered in 60±5.8 and 83.3±12.0 of cysts treated during 4 days with 50 and 100μg/ml, respectively. The half maximal effective concentration (EC50) value of the S. aristata extract against E. granulosus (s.s.) cysts was 47.86μg/mL (96h). The dosage of infected animals with the 50mg kg⁻¹ dose of S. aristata extract resulted in a significant reduction in cyst weight in comparison with the control group. In conclusion, S. aristata extract was demonstrated to exert a marked effect, both in vitro and in the murine model.