Clinical, gross, and microscopic findings in 7 owl monkeys ( Aotus spp ) with chronic biliary tree disease

that range across a wide variety of arboreal habitats from Central to South America. Owl monkeys are an important animal model for malaria research. Despite decades of use as a laboratory animal model, disease of the hepatobiliary system is rarely described in this species. The exception is cholelithiasis, which has been reported in the species as an incidental finding with minimal serum chemistry derangements or histologic evidence of disease. However, a retrospective analysis of clinical histories and necropsy reports from owl monkeys housed at the Keeling Center as part of the Owl Monkey Breeding and Research Resource identified 7 cases of obstructive hepatopathy associated with chronic cholecystitis (3/7) and cholelithiasis (4/7). Secondary sclerosing cholangitis was identified in 3/7 monkeys. Elevated gamma-glutamyl transferase was associated with obstructive disease and was increased in 6/6 animals with available bloodwork. Gross lesions included gallbladder distension (5/7), cystic dilation of the common bile duct (1/7), and gallbladder atrophy (1/7). Histologic lesions included moderate to severe submucosal and periductular fibrosis, bile duct hyperplasia, biliary mucosal hyperplasia, and luminal narrowing. A single case had squamous metaplasia of the gallbladder, intrahepatic duct, and common bile duct epithelium. This report defines the clinical syndrome associated with obstructive biliary disease, including ultrasound and serum chemistry derangements, and describes the associated gross and microscopic lesions.