Agent-based simulation of seasonal malaria chemoprevention strategy in Southern Tanzania: comparing dihydroartemisinin-piperaquine with or without primaquine

Background: The effect of seasonal malaria chemoprevention (SMC) strategy on malaria transmission using a single low dose of primaquine (SLDPQ) added to artemisinin-based combination therapy has not been established in Africa. An agent-based model and simulation (ABMS) was used to assess SMC effectiveness using dihydroartemisinin-piperaquine (DP) with and without SLDPQ in Masasi and Nanyumbu Districts, Tanzania.

Methods: ABMS was developed in AnyLogic platform using secondary data from a cluster-randomized DP-based SMC study conducted in the districts, to assess the effectiveness of DP with and without SLDPQ for control of malaria in under-five children. The model incorporated human, mosquito, transmission, intervention, and environment sub-models, and simulated three monthly rounds of SMC over a 180-day period. Environment temperature, an important factor in mosquito breeding was simulated in three scenarios, first using average field temperature, and then when it was increased or decreased by 10C from the average. Model outputs were compared with field results to evaluate external validity.

Results: Overall, 2275 participants, 1135 in the intervention and 1140 in the control arm were involved in the model. At baseline, malaria prevalence was 11.5% (130/1135) and 16.3% (186/1140) in the intervention and control arm, respectively. At the end of 125-day simulation period malaria prevalence declined to 4.1% (47/1135), and it rebounded to 7.1% (80/1135) at the end of 180-day simulation period after three rounds of DP alone administration. Addition of SLDPQ to DP led to a further declined of the prevalence to 1.4% (16/1135) and 3.9% (44/1135) at the end of 125-day and 180-day, respectively. In the DP alone, the increase in average temperature by 1˚C further decreased malaria prevalence to 2.6% (30/1135) and 5.0% (57/1135) at the end of 125-day and 180-day, respectively, whereas the decrease of temperature by 1 ˚C decreased the malaria prevalence to 3.2% (36/1135) and 4.2% (48/1135) at the end of 125-day and 180-day, respectively.

Conclusions: The ABMS has demonstrated that addition of SLDPQ to DP reduced malaria transmission significantly regardless of the increase or decrease of the average temperature by 1 ˚C. SLDPQ can be added to DP-SMC and scaled-out for the control of malaria in Tanzania.

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