Pulmonary pneumocystosis in nonhuman primates.

Pulmonary infection with Pneumocystis carinii was detected in two aged owl monkeys (Aotus trivirgatus) and two young chimpanzees (Pan troglodytes). The clinical histories of the owl monkeys were similar and included progressive weight loss, anorexia, failure to thrive, and death. One of the owl monkeys had no concurrent disease, whereas the other had been experimentally inoculated with Treponema pallidum 44 months before death. In both chimpanzees, an underlying myeloproliferative malignant neoplasm was associated with Pneumocystis infection. Pneumocystis organisms were found in alveolar spaces and alveolar lining cells by light and electron microscopy. Pathologic features of these untreated cases and a case in a chimpanzee treated with pentamidine isethionate were similar to those described in humans. To our knowledge, this is the first report of pulmonary pneumocystosis associated with death in nonhuman primates.