Naturally Occurring Helicobacter pylori Infection in the Cynomolgus Monkey (Macaca fascicularis) Used in Subclinical Studies

Recently, a high incidence of naturally occurring Helicobacter pylori (H. pylori)-related gastritis was reported in a cynomolgus monkey colony (Reindel et al., 1999). We retrospectively examined 82 cynomolgus monkeys from three different countries. These monkeys were used in toxicological or pharmaceutical studies in our laboratory. Diffuse antral gastritis was observed in 49 of 58 (84%) animals of Group A in the Philippines, and two of 10 (20%) of Group C in Japan. In their antrum, the mucosal layer was thickened with lymphocytic and plasmacytic infiltration, and enlarged lymphoid follicles. However, no erosion or hemorrhage was seen in the lesions. H. pylori-like bacteria were detected by Warthin-Starry staining in almost all of the monkeys showing antral gastritis. No histological changes or H. pylori-like bacteria were detected in the animals of Group B in Indonesia. In conclusion, although the incidence of infection may be in part due to the breeder, natural infection of H. pylori was confirmed in cynomolgus monkeys. Thus, this species as well as rhesus monkeys may be useful in the study of H. pylori infection. Moreover, because of its high incidence, the colony in the Philippines may be suitable for an animal model, as it is comparable with natural infection in humans.