FATAL INFECTIONS WITH BALAMUTHIA-MANDRILLARIS (A FREE-LIVING AMEBA) IN GORILLAS AND OTHER OLD-WORLD PRIMATES

Balamuthia mandrillaris is a newly described free-living amoeba capabl e of causing fatal meningoencephalitis in humans and animals. Because the number of human cases is rapidly increasing, this infection is now considered an important emerging disease by the medical community. A retrospective review of the pathology database for the Zoological Soci ety of San Diego (the San Diego Zoo and San Diego Wild Animal Park) fo r the period July 1965 through December 1994 revealed five cases of am oebic meningoencephalitis, all in Old World primates. The infected ani mals were a 3-year, 10-month-old female mandrill (Papio sphinx), from which the original isolation of B. mandrillaris was made, a 5-year-old male white-cheeked gibbon (Hylobates concolor leucogenys), a 1-year-o ld female western lowland gorilla (Gorilla gorilla gorilla), a 13-year , 5-month-old male western lowland gorilla, and a 6-year-old female Ki kuyu colobus monkey (Colobus guereza kikuyuensis). Two different disea se patterns were identified: the gibbon, mandrill, and 1-year-old gori lla had an acute to subacute necrotizing amoebic meningoencephalitis w ith a short clinical course, and the adult gorilla and colobus monkey had a granulomatous amoebic meningoencephalitis with extraneural fibro granulomatous inflammatory lesions and a long clinical course. Indirec t immunofluorescent staining of amoebas in brain sections with a Balam uthia-specific polyclonal antibody was positive in all five animals. I ndirect immunofluorescent staining for several species of Acanthamoeba , Naegleria fowleri, and Hartmanella vermiformis was negative. Direct examination of water and soil samples from the gorilla and former mand rill enclosures revealed unidentified amoebas in 11/27 samples, but in traperitoneal inoculations in mice failed to induce disease. Attempts to isolate amoebas from frozen tissues from the adult male gorilla wer e unsuccessful.