BACKGROUND AND OBJECTIVE: Giardiasis is one of the most common infections of the gastric tract in the world, which is caused by protozoa. Today, metronidazole, furazolidun, tinidazole and quinacrine are commonly used to treat this disease. These medications are associated with several adverse side effects and finding an alternative solution with fewer side effects seems necessary. The present study aims to analyze the effect of hydroalcoholic extract of rosemary (Rosmarinus officinalis) on the cysts of Giardia lamblia parasite under in vitro conditions.

METHODS: In this experimental study, 25 mice were categorized into 5 groups (n=5) including negative control group, positive control group (treated with metronidazole) and other three treatment groups (treated with 100, 200 and 400 mg/ml rosemary extract). Then, the effect of hydroalcoholic extract of rosemary was analyzed until the tenth day.

FINDINGS: According to the results of this study, the body weight of the mice in the groups treated with hydroalcoholic extract of rosemary (20.78 - 26.64) was less than control group (28.70 ± 0.69), which received no medication (p<0.0001). Investigating the effect of rosemary extract on Giardia lamblia parasite demonstrated that decline in the number of cysts in 100, 200 and 400 mg/ml groups were 70.7, 80.6 and 94%, respectively (p<0.05).

CONCLUSION: Results of the present study demonstrated that rosemary has proper in vivo effects and can be considered as a suitable alternative for treatment of Giardiasis.