Combination therapy of green synthesized copper nanoparticle and metronidazole showed promising efficacy against Giardia lamblia infection.

Numerous studies have explored the effects of nanoparticles on Giardia lamblia under in vitro and in vivo conditions, yet the findings remain inconsistent and incomplete due to the limited use of animal models. Green-synthesized copper nanoparticles (GSCNP) have shown broad-spectrum antimicrobial properties against bacteria, fungi, viruses, and parasites, including Leishmania, Echinococcus, and Toxoplasma gondii. This study investigated the anti-giardial efficacy of GSCNP biosynthesized using Rumex vesicarius extract, alone and in combination with metronidazole (MZ), in a murine model of giardiasis. GSCNP were synthesized via a hydroalcoholic extract of R. vesicarius acting as a reducing and capping agent. Treatments with GSCNP (5, 10, and 20 mg/kg), alone or combined with MZ (7.5 or 15 mg/kg), were assessed for cyst load, enzyme and electrolyte profiles, cytokine responses (IL-17, IFN-γ), secretory IgA, and apoptosis-related gene expression. Co-administration of GSCNP (20 mg/kg) with MNZ (7.5 mg/kg) significantly reduced cyst excretion (p < 0.05), achieving complete cyst elimination compared to MZ monotherapies (15 mg/kg = 12.3 cysts; 7.5 mg/kg = 39.6 cysts). This combination normalized serum Na (148.9 mEq/L), K (5.6 mEq/L), Cl (112.7 mEq/L), α-amylase (271.7 mU/mL), and lipase (5.8 mU/mL), while markedly elevating IL-17 (323.6 pg/mL) and IFN-γ (445.7 pg/mL) levels (p < 0.001). Gene expression analysis revealed upregulation of BCL-2 (5.97-fold) and moderate increases in caspase-3 (1.09-fold) and BAX (1.04-fold). These findings demonstrate that GSCNP, particularly in combination with subtherapeutic MZ, enhances anti-giardial efficacy through immunomodulatory and anti-apoptotic mechanisms, supporting their potential as a novel adjunctive therapy for giardiasis.