Clinicopathologic study of six cases of meningitis and meningoencephalitis in chimpanzees (Pan troglodytes).

Three fatal cases of purulent meningitis and one fatal case of thromboembolic necrotizing meningoencephalitis occurred in chimpanzees from the Primate Center TNO, The Netherlands. In addition, two apes had clinical signs of meningitis and were successfully treated. The severity of the residual hemiparesis and dysphagia in one of these two apes was such that it was killed for humane reasons. The histopathological diagnosis was chronic active meningoencephalitis. Streptococcus pneumoniae was isolated from five apes and Klebsiella pneumoniae from one. In the majority of cases, the primary site of infection was the upper respiratory tract. After reducing the population density, initiating a vaccination program using a commercially available human polyvalent pneumococcal vaccine, and changing the cleaning procedure of the animal facilities, no other cases of meningitis or meningoencephalitis have occurred in the chimpanzee colony in the ensuing 3.5 years.