Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 20 4 2025 12 07 517 523 EN Seyed Reza Mirbadie 1. Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran 2. School of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran Salman Zafari Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Naghmeh Dastan Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran Mohammad Fallah Department of Medical Parasitology and Mycology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran 2024 12 06 2025 12 07 Background: Laboratory animals are widely used for medical research; hence, their health status is a determinant of the outcome and success of the research. We aimed to investigate the possible infection of rodents with intestinal parasites in the Hamadan University of Medical Sciences animal house. Methods: From October to November 2022, one hundred and twenty healthy laboratory rodents including 60 Wistar rats, 30 BALB/c mice, and 30 NMRI mice were randomly collected and examined for parasitic infections. The digestive tracts were removed and examined for infection by helminths and parasitic protozoa using naked eye inspection and microscopy. Results: 75.8% (95% CI: 68.1–83.5%) of the rodents were infected by at least one helminth or protozoa. Protozoal infections (41.7%) with Giardia spp. (15%), Tritrichomonas spp.(10%), Blastocystis spp. (6.7%), Entamoeba spp. (5.9%), Cryptosporidium spp. (3.3%), and Eimeria spp. (0.8%) were observed relatively higher than helminthic infections (34.2%) with Syphacia obvelata (10.8%), Syphacia muris (10%), Aspiculuris tetraptera (7.5%), Hymenolepis nana (3.3%), and Hymenolepis diminuta (2.5%). Conclusion: This study showed high parasitic infection without clinical signs in laboratory rodents. Therefore, monitoring these animals and improving their breeding conditions can eliminate the adverse effects of these parasitic infections in the animal research processes and improve the health of researchers and staff. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4468 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4468/1460