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Table 3 Association of Anopheles funestus densities with different IRS insecticides supplementing LLINs upon months before, during and when not spraying

From: Incremental impact upon malaria transmission of supplementing pyrethroid-impregnated long-lasting insecticidal nets with indoor residual spraying using pyrethroids or the organophosphate, pirimiphos methyl

Indoor residual spraying insecticide treatment regimen Absolute numbers caught Mean catchesa Relative biting rates of An. funestus
[95 % Confidence interval (CI)] (RR)a [95 % CI] P value
Deltamethrin WG)
 1–3 months since last spray 73 0.112 [0.641, 0.371] 0.99 [0.63, 1.56] 0.897
 4–6 months since last spray 1229 0.641 [0.371, 1.109] 3.98 [3.15, 5.04] <0.001
 7–12 months since last spray 134 0.111 [0.062, 0.199] 0.86 [0.64, 1.17] 0.067
 >12 months since last spray or never 1186 0.189 [0.113, 0.317] 1 [NA]b NAb
Lambdacyhalothrin CS
 1–3 months since last spray 20 0.191 [0.090, 0.405] 1.03 [0.56, 1.88] 0.805
 4–6 months since last spray 6 0.055 [0.022, 0.141] 0.17 [0.08, 0.39] <0.001
 7–12 months since last spray 0 NEc NEc 0.972
 >12 months since last spray or never 182 0.198 [0.121] 1 [NA]b NAb
Pirimiphosmethyl EC
 1–3 months since last spray 478 0.234 [0.131, 0.417] 1.04 [0.83, 1.30] 0.786
 4–6 months since last spray 346 0.055 [0.030, 0.098] 0.25 [0.20, 0.33] <0.001
 7–12 months since last spray 160 0.159 [0.086, 0.293] 0.69 [0.50, 0.95] 0.151
 >12 months since last spray or never 2823 0.234 [0.131, 0.417] 1 [NA]b NAb
Pirimiphosmethyl CS
 1–3 months since last spray 14 0.021 [0.009, 0.047] 0.07 [0.04, 0.13] <0.001
 4–6 months since last spray 70 0.004 [0.002, 0.008] 0.02 [0.01, 0.02] <0.001
 7–12 months since last spray NEc NEc NEc NEc
 >12 months since last spray or never 2087 0.253 [0.152, 0.422] 1 [NA]b NA
  1. NA Not applicable because reference group, NE Not estimable because no spraying of this insecticide regimen was conducted early enough to yield impact data beyond 6 months post-spray but before the following spray round so no data are available for estimation
  2. aThe effect of different IRS treatment regimens on the mean catches of An. funestus species where estimated by fitting generalized linear mixed models (GLMMs) with An. funestus catches treated as dependent variables. The households where nested within villages which were also nested within the clusters, these together with date were treated as random effects, while the different IRS treatment regimens were categorized as independent variables. A Poisson distribution with no intercept was used to estimate the mean catches while an intercept was included in estimating the RR