Abstract Lawsonia intracellularis is a Gram-negative rod responsible for causing proliferative ileitis in hamsters and other species of domestic animals. It is a common and often lethal disease in hamsters. This article gives a detailed description of the organism along with the clinical signs, gross and histopathologic findings, diagnostic techniques, and treatment options of the disease as it affects exotic mammal patients. In addition, identification of this bacterial disease in other species is discussed, along with its zoonotic potential.