Faezeh Najafi - Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
Maede Taghavi Ghadikolai - Department of Biology, Faculty of Sciences, University of Mohaghegh Ardabili, Ardabil, Iran
Saied Reza Naddaf - Department of Parasitology, Research Center for Emerging and Reemerging Diseases Pasteur Institute of Iran, Tehran, Iran
Hamid Hasanpour - Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
Iraj Mobedi - Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
Gholamreza Mowlavi - Department of Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

Introduction: Some postgraduate students reported the presence of a nematode infection, presumably, Trichosomoides crassicauda in the urinary bladder of rats (Rattus norvegicus) from the animal house of Tehran University of Medical Sciences (TUMS). We prompted to explore the prevalence of this infection among the rats of animal houses belonging to medical and veterinary research centers in Tehran. We also described the histopathological changes in the bladder tissue of the infected rats. Methods: We collected ۲۱۴ adult rats (R. norvegicus) from four animal houses including TUMS in Tehran. The urine of ۱۱۲ animals was collected during ۲۴ h and inspected microscopically for helminths eggs. Then, the rats were euthanized, sacrificed and dissected; their bladders were removed and examined under a stereomicroscope for the presence of worms and histopathological changes. Results: Out of ۱۱۲ urine samples checked, ۱۶ contained T. crassicauda eggs. Out of ۲۱۴ rats, ۱۱۴ showed infection urinary bladder with the nematode T. crassicauda. The histopathological changes in the urinary bladder included hyperemia, edema, hyperplasia, and metaplasia. In the transitional epithelium, the features of gravid female nematodes, with an egg-filled uterus were visible. Conclusion: Trichosomoides crassicauda is a prevalent infection in laboratory rats of research centers in Tehran and its identification cannot be made merely based on urine examination of the rats.

Trichosomoides crassicauda, Laboratory Rats, Histopathological Changes