Trichosomoides crassicauda Infection in Laboratory Rats with Histopathological Description in the Bladder Tissue

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 214 adult rats (R. norvegicus) from four animal houses including TUMS in Tehran. The urine of 112 animals was collected during 24 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 112 urine samples checked, 16 contained T. crassicauda eggs. Out of 214 rats, 114 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.