Estimation of changes in the force of infection for intestinal and urogenital schistosomiasis in countries with schistosomiasis control initiative-assisted programmes

Table 3 Relative (to baseline) changes in the force of infection (FOI) and their 95 % confidence intervals estimated at the point of monitoring (one or two years) after each round of preventive chemotherapy with praziquantel for Schistosoma haematobium areas

Country	BL Infection Intensity Category	Number in cohort (n)	BL infection Intensity (epg)	BL FOI (wppy)	FY1 ζ₁	FY2 ζ₂	FY3 ζ₃
Country	BL Infection Intensity Category	Number in cohort (n)	BL infection Intensity (epg)	BL FOI (wppy)	[95 % CI]	[95 % CI]	[95 % CI]
Burkina Faso	High	376	124.46	20.03	0.013 [0.0005, 0.12]^a	0.124 [0.04, 0.21]^a	0.048 [0.02, 0.12]^a
Burkina Faso	Low	188	17.11	1.69	0.005 [0.0003, 0.14]^a	0.253 [0.08, 0.56]^a	0.001 [0.0003, 0.10]^a
Mali	High	591	174.15	9.37	0.27 [0.11, 0.62]^a	0.30 [0.11, 0.68]^a	NA
Mali	Low	561	19.67	1.53	0.70 [0.32, 1.34]	0.17 [0.05, 0.44]^a	NA
Niger	High	270	121.87	1.91	0.70 [0.23, 1.42]	0.86 [0.23, 1.88]	NA
Niger	Low	1047	20.76	0.63	0.18 [0.10, 0.35]^a	0.36 [0.21, 0.76]^a	NA
Tanzania	All (Low)	664	11.06	1.22	0.584 [0.22, 0.91]^a	0.434 [0.21, 0.80]^a
Zambia	High	276	89.11	1.53	0.730 [0.21, 1.65]	NA	NA
Zambia	Low	1169	10.01	0.38	2.129 [0.89, 4.21]	NA	NA

FOI :force of infection expressed as the mean number of adult female parasites acquired per person per year; e/10 ml: eggs per 10 ml of urine; wppy: worms per person per year; BL: baseline; FY1: follow-up year 1; FY2: follow-up year 2; FY3: follow-up year 3; ζ₁, ζ₂, ζ₃: the relative change in the FOI at FY1, FY2, FY3 respectively, expressed as a proportion of that at baseline; ^asignificant decreases in FOI from baseline: NA: not available. In Tanzania there was no treatment or survey at FY2 so the data collected at FY3 comprise an average across the previous two years. In Burkina Faso there was no treatment following FY1 so the results at FY1 and FY2 constitute two successive years following a single treatment round

ISSN: 1756-3305