Predisposition to Ascaris lumbricoides reinfection in the Geshiyaro project in southern Ethiopia

OBJECTIVES: Predisposition to reinfection is characterized by certain individuals repeatedly acquiring infection at higher rates than others in the population despite treatment. As endemic regions approach low prevalence levels, such individuals will act as reservoirs of infection and contribute to sustaining transmission cycles in communities. This study investigated evidence for individual-level predisposition to Ascaris lumbricoides infections using longitudinal data from the Geshiyaro project in southern Ethiopia. METHODS: Longitudinal parasitological data collected over 7 years were analysed. Kendall's tau (τ) correlation coefficient was used to assess temporal persistence of infection between successive survey rounds, and Kendall's coefficient of concordance (W) was used to evaluate long-term stability in individuals' relative infection risk over many years of survey rounds. RESULTS: Positive correlations in infection status between survey rounds were observed (τ = 0.10-0.30, P < .001). Moderate concordance in infection ranking across the study period was also detected (W = 0.43, 95% CI: 0.42-0.45; P < .001), indicating persistent individual-level predisposition over many years of treatment and reinfection. CONCLUSION: These findings demonstrate sustained heterogeneity in infection risk within endemic communities. As transmission declines, identifying individuals predisposed to reinfection may help inform targeted or complementary 'test-and-treat' strategies to support interruption of A. lumbricoides transmission.