RESUMEN
A 5-year-old male cross-bred guard dog with signs of anorexia, vomiting and jaundice was referred to Small Animal Hospital, Faculty of Veterinary Medicine, University of Tehran. Initial diagnostic laboratory tests revealed leukocytosis, thrombocytopenia, haemoconcentration, azotaemia, high liver enzyme activities, proteinuria and bilirubinuria. Aggressive therapeutic procedures failed to improve the animal deteriorated condition and finally the animal died. After necropsy, specimens were collected for microscopic examination as part of completing diagnostic procedures. Results of urine bacterial culture confirmed leptospirosis as a causative agent. Furthermore, numerous large spiral bacteria were also observed under dark-field microscope. This article summarizes and characterizes the historical and physical findings, laboratory data, bacterial culture and pathological diagnostic features of leptospirosis in the cross-bred dog. Based on published data, this is the first case of confirmed Leptospira isolation from a dog in Iran