Spontaneous lesions and parasites of the Mongolian gerbil, Meriones unguiculatus.

Four-hundred-eighty Mongolian gerbils, Meriones unguiculatus [Uclp:(MON)], most of which were experimentally infected with filarial worms, were examined for spontaneous lesions. Previously unrecognized lesions included cutaneous squamous cell carcinoma, duodenal adenocarcinoma, malignant blue nevus, hepatic choleangiocarcinoma, malignant hemangiopericytoma of the uterus, ovarian teratoma, chronic interstitial nephritis, renal cortical retention cysts, splenic hemangiomas, and various histologic abnormalities of the lung. Previously reported lesions also seen in the present study were a malignant melanoma, adrenal cortical adenoma or carcinoma, uterine leiomyoma, sebaceous gland adenoma, hepatic lymphangioma, and renal hemangioma. Hymenolepis diminuta (Cestoda) and Tyrophagus castellani (Acarina) were accidentally recovered from experimental animals. Tritichomonas caviae and a species of Entamoeba were the most common intestinal protozoa. Tyzzer's disease, however, was clearly the most significant infectious disease of gerbils in the UCLA School of Public Health colony.