Entamoeba dispar, but not E-histolytica, detected in a colony of chimpanzees in Japan

Chimpanzees (Pan troglodytes) residing in the Kumamoto Primate Research Par k, Sanwa Kagaku Kenkyusho, were surveyed for the presence of intestinal par asites. Stool samples from 107 chimpanzees were examined by microscopy afte r formalin-ether sedimentation. Of these animals, 100 were infected with at least 1 species of ameba. The positivity rates recorded were as follows: E ntamoeba coli, 88%; E. histolytica/E. dispar, 48%; E. hartmanni, 15%; Iodam oeba buetschlii, 8%; Endolimax nana, 4%; and Entamoeba chattoni, 2%. Polyme rase chain reaction (PCR) analysis to distinguish between E. histolytica an d E. dispar was performed on these samples. E, dispar DNA was detected in 6 0 of 107 samples (56%), including 9 that had been microscopically determine d to be negative for E. histolytica/E. dispar. In contrast, no E. histolyti ca DNA was detected in the 107 samples. Zymodeme analysis indicated that 10 isolates were E. dispar. When 104 chimpanzees were examined serologically for E. histolytica infection, 1 sample was scored as positive by indirect h emagglutination and another was found to de positive by an indirect fluores cent antibody test. However, both specimens were borderline-positive and we re clearly negative in other tests, suggesting that they might be false-pos itives. These results demonstrate that the pathogenic E. histolytica was ab sent in this colony, regardless of the high degree of prevalence of other a mebas. For an accurate diagnosis, PCR analysis is recommended in addition t o microscopic examination.