Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 20 1 2025 02 27 100 110 Mohammad Amin Ghobadi Student Research Committee, Lorestan University of Medical Sciences, Khorramabad, Iran Hossein Mahmoudvand Razi Herbal Medicines Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran Amal Khudair Khalaf Department of Microbiology, College of Medicine, University of Thi-qar, Thi-qar, Iraq Fatemeh Azadbakht Student Research Committee, Lorestan University of Medical Sciences, Khorramabad, Iran Marzieh Rashidipour Razi Herbal Medicines Research Center, Lorestan University of Medical Sciences, Khorramabad, Iran Iraj Salimikia Department of Pharmacognosy, Lorestan University of Medical Sciences, Khorramabad, Iran 2024 09 05 2025 01 26 Background: Given the significant role of chitosan nanoparticles in medicine, the present study aimed to assess the in vivo efficacy of synthesized chitosan nanoparticles coated with thymol (CNCT) in combating Toxoplasma gondii infection. Methods: Mice were administered CNCT orally at dosages ranging from 0.25 to 0.75 mg/kg/day for a duration of 14 days. Following this treatment, they were infected with T. gondii tachyzoites of the Rh strain to induce acute toxoplasmosis. Then, the mortality rate, parasite load, antioxidant activity, and the gene expression level of proinflammatory cytokines were evaluated. Results: The dimensions of CNTN exhibit variability, with a mean size of 295 nm. The prophylactic administration of CNTN in mice infected with T. gondii resulted in a significant enhancement in survival rates and a considerable decrease in parasite load (P<0.001). The CNTN caused a significant decrease in malondialdehyde level, while a notable increase (P < 0.001) in the activity of the antioxidant enzymes. The feeding the mice infected with CNTN caused a meaningful elevation in the expression level of TNFα- and IL-1β (P<0.001). The biochemical analyses indicated no significant changes in the serum levels of liver and kidney function markers. Conclusion: The recent study revealed that CNTN demonstrates promising in vivo effects against toxoplasmosis in murine models. These effects are attributed to its antioxidant properties and immunomodulatory capabilities, which increase specific pro-inflammatory cytokines without any noticeable signs of toxicity to liver and kidney function. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4355 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4355/1413