Clonorchis sinensis re-infection rate and the determinants: a prospective cohort study in Hengxian County, Guangxi, China.

BACKGROUND To understand Clonorchis sinensis re-infection and the determinants in endemic areas is important in establishment of control measures. METHODS A prospective cohort study was implemented in Hengxian County, Guangxi, China. Individuals with C. sinensis infection were completely treated, and those cured were enrolled as study subjects and followed up for 3, 6 and 12 months. The re-infection frequency and incidence were calculated, and a multivariable Cox proportional hazard model was constructed to capture re-infection determinants. RESULTS Among 635 enrolled subjects, 436 (68.7%) completed follow-up. Of these, 177 (40.6%) were re-infected; 133 (75.1%) were re-infected once, 41 (23.2%) twice and 3 (1.7%) three times. The incidence of re-infection was 64.0 per 100 person-years. Males (aHR: 1.67, 95% CI: 1.14-2.44), those with underlying diseases (aHR: 1.41, 95% CI: 1.02-1.95), and those with moderate- and heavy-intensity infections (aHR: 1.45, 95% CI: 1.14-1.85) had increasing re-infection probabilities. CONCLUSIONS C. sinensis re-infection is high in endemic areas. Males and high-intensity infection are important determinants of re-infection. Repeated chemotherapy is necessary to control re-infection and its associated morbidities, especially in high-risk individuals. In addition, behavioural education is advised to decrease overall re-infection in endemic areas.