Control and elimination of schistosomiasis as a public health problem thresholds fail to differentiate schistosomiasis morbidity prevalence in children

Abstract Background Current World Health Organization guidelines utilize prevalence of heavy-intensity infections (PHI), i.e., ≥50 eggs per 10ml of urine for Schistosoma haematobium and ≥400 eggs per gram of stool for S. mansoni, to determine whether a targeted area has controlled schistosomiasis morbidity or eliminated schistosomiasis as a public health problem. The relationship between these PHI categories and morbidity is not well understood. Methods School-aged participants enrolled in schistosomiasis monitoring and evaluation cohorts from 2003-2008 in Burkina Faso, Mali, Niger, Uganda, Tanzania, and Zambia were surveyed for infection and morbidity at baseline and after 1 and 2 rounds of preventive chemotherapy. Logistic regression was used to compare morbidity prevalence among participants based on their school’s PHI category. Findings Microhematuria levels were associated with the S. haematobium PHI categories at all three time points. For any other S. haematobium or S. mansoni morbidity that was measured, PHI categories did not differentiate morbidity prevalence levels consistently. Interpretation These analyses suggest that current PHI categorizations do not differentiate the prevalence of standard morbidity markers. A reevaluation of the criteria for schistosomiasis control is warranted. Funding The Schistosomiasis Control Initiative (now the SCI Foundation) was supported by the Bill and Melinda Gates Foundation (grant 13122).