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Table 3 Summary of S. haematobium infection by study arm from baseline to Year 5 (9–12 years-old cross-section only)

From: Evaluating the impact of biannual school-based and community-wide treatment on urogenital schistosomiasis in Niger

Variable Groupa Total
A1 A2 B1 B2 C1 C2
No. of villages sampled 38 37 37 38 37 38 225
No. tested at baseline 3461 3221 3659 3671 3357 3562 20,931
No. infected at baseline 129 148 898 825 480 834 3314
Prevalence at baseline (%) 3.7 4.6 24.5 22.5 14.3 23.4 15.8
Prevalence of heavy infection at baseline (%) 0.29 0.28 1.86 1.93 0.86 2.50 1.29
No. tested at Year 5 3710 3648 3621 3740 3689 3724 22,132
No. infected at Year 5 22 9 839 503 425 392 2190
Prevalence at Year 5 (%) 0.6 0.2 23.2 13.4 11.5 10.5 9.90
Prevalence of heavy infection at Year 5 (%) 0.13 0.03 1.77 0.64 0.57 0.83 0.66
Absolute difference in prevalence at Year 5 and baseline −3.1 −4.4 −1.3 −9.1 −2.8 −12.9 −5.90
 Relative difference in prevalence at Year 5 and baseline (% change) −83.8 −95.7 −5.3 −40.4 −19.6  −55.1 −37.3
 Village-level arithmetic mean infection intensity at baselineb 0.77 0.52 4.11 5.1 1.78 5.37 2.94
 Village-level arithmetic mean infection intensity at Year 5b 0.14 0.05 3.62 1.39 1.37 2.18 1.46
Egg reduction rate (1-Year 5 intensity/baseline) 0.82 0.9 0.12 0.73 0.23 0.59 0.57
 Individual-level arithmetic mean infection intensity at baselinec 0.84 0.58 4.05 4.91 1.85 5.64 2.98
 Individual-level arithmetic mean infection intensity at Year 5c 0.14 0.05 3.61 1.38 1.37 2.2 1.46
  1. aStudy arms: Low prevalence areas receiving SBT once a year (A1), and twice a year (A2); high prevalence areas receiving SBT once a year (B1), and twice a year (B2); and high prevalence areas receiving CWT once a year (C1), and twice a year (C2)
  2. bVillage-level intensity: This is the mean egg count for all tested 9–12 year-old subjects (including those with zero egg counts), which is a measure of community level contamination potential
  3. cIndividual-level intensity: This is the mean egg count among egg-positive 9–12 year-old subjects, which is an estimate of the intensity of infection among known active cases
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Parasites & Vectors

ISSN: 1756-3305

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