Prevalence of asymptomatic Tropheryma whipplei carriage among humans and nonhuman primates

Background. The reservoir of the agent of Whipple disease is unknown. Asymptomatic carriage of Tropheryma whipplei in human stool and saliva is controversial. Methods. Stools and saliva specimens from 231 workers at a sewage treatment facility and from 10 patients with Whipple disease, stool specimens from 102 healthy people, and stool specimens from 127 monkeys or apes were tested for T. whipplei DNA by a quantitative real-time polymerase chain reaction with probe detection. Genotyping and culture of T. whipplei-positive samples were performed. Results. Asymptomatic carriage in stool was found in humans (ranging from a prevalence of 4% in the control group to 12% among a subgroup of sewer workers) but not in monkeys and apes. The T. whipplei load in stool was significantly lower in carriers than in patients with Whipple disease (P < .001). There was a significant prevalence gradient associated with employment responsibilities at the sewage treatment facility: workers who cleaned the underground portion of the sewers were more likely than other workers to carry T. whipplei in stool. Seven of 9 sewer workers tested positive 8 months later. Patients with Whipple disease were significantly more likely to have T. whipplei-positive saliva specimens (P = .005) and had a significantly greater T. whipplei load in saliva (P = .015), compared with asymptomatic stool carriers from the sewage facility. All non-stool carriers had T. whipplei-negative saliva specimens. T. whipplei strains were heterogeneic among sewer workers but identical within individual workers. Conclusion. Chronic asymptomatic carriage of T. whipplei occurs in humans. Bacterial loads are lower in asymptomatic carriers, and the prevalence of carriage increases with exposure to sewage.