Abstract
A young adult chimpanzee died after a brief gastrointestinal illness characterized by profuse soft stool, vomiting and dyspnoea. Necropsy examination revealed a severe typhlitis and colitis with pseudomembrane formation, and acute aspiration pneumonia. Balantidium coli, a common intestinal parasite, was found in large numbers in the mucosal and submucosal layers of the colon and caecum. The inflammation and degree of invasion associated with Balantidium coli indicates that it was a primary pathogen.