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Table 5 The impact of resistance on control interventions that target a single stage of the life-cycle. This is quantified by adult mosquito population size

From: Modelling the impact of insecticide-based control interventions on the evolution of insecticide resistance and disease transmission

Intervention [parameter] Adult population size; SS genotypes Resistance calibration Adult population size; RR genotypes Population re-established? Transmission restarts? (R0)
Larviciding [ρl] 0 (877) Top left panel of Fig. 5 10,711 (877) Yes Yes (12)
Pupacide [ρp] 0 (877) Top right panel of Fig. 5 5483 (877) Yes Yes (6.3)
IRS [ρn] 0 (71,767) Lower left panel of Fig. 5 29,636 (15,946) Yes Yes (1.8)
ITN [ρs] 0 (97,845) Lower right panel of Fig. 5 2502 (5113) Yes No (< 1)
  1. The column “Adult population size; SS genotypes” shows the equilibrium female mosquito population sizes post-intervention assuming no resistance is present (i.e. only SS genotypes) and, in brackets, the critical adult female population size required to block malaria transmission using the Ross-Macdonald approach (i.e. M’, obtained from Eq. 22); all these interventions eradicated the local mosquito population and hence stopped malaria transmission. The column “Adult population size; RR genotypes” gives the equivalent values of population size and M’ but assuming only RR genotypes are present. The parameterisations are as shown in the panel captions of Fig. 5; for example, the first row of this Table is equivalent to the top left panel of Fig. 5, i.e. the values are calibrated by assuming that the insecticide intervention reduces larval survival ρl of the SS genotype by 30% while the RR and RS genotypes are less affected by insecticide and their larval survival during the intervention is 10% lower than in the absence of insecticide. Comparison of the “SS genotypes” with the “RR genotypes” column reveals whether the spread of resistance during the interventions shown in Fig. 5 is sufficient for mosquito populations to become re-established (we define this as a greater than 100-fold increase in adult female numbers) and, if so, whether they recover to the extent that malaria transmission restarts. If transmission does restart, we give estimated R0 (from Eq. 19) to quantify the magnitude of this resurgence (baseline before control, was R0 = 155)