The asymptomatic parasite reservoir and targeted mass drug administration in the context of accelerated malaria elimination in western Cambodia

The emergence and spread of multidrug-resistant Plasmodium falciparum has caused serious concern to current global elimination initiatives. If not eliminated, resistant parasites could eventually spread to Africa. We, therefore, conducted a series of studies in western Cambodia to describe the epidemiology of asymptomatic Plasmodium infections, and to evaluate the safety, efficacy, effectiveness and acceptability of mass drug administration (MDA) with dihydroartemisinin-piperaquine (DHA-PPQ) in an area of multidrug-resistant P. falciparum.
In Section I, we showed that subclinical Plasmodium vivax persist longer than P. falciparum in low transmission setting. Asymptomatic Parasite densities fluctuates over time to become infectious and may sustain malaria transmission. Asymptomatic Plasmodium infections were associated with moderately elevated plasma CRP concentrations, chiefly with P. vivax infections. Spatial clustering within the villages was transient, making the prediction of spatial clusters difficult. In Section II, We showed heterogeneity in the malaria parasite reservoir, and Plasmodium prevalence correlated with subsequent malaria incidence chiefly to P. vivax. Three-monthly rounds of MDA with DHA-PPQ achieved high coverage in low transmission areas, and were safe and well tolerated. MDA was associated with the absence of clinical P. falciparum cases for at least 1 year. In Section III, we showed that building trust and friendship with the villagers, and involving the community in planning and implementation were essential to persuade the community to take part in MDA. We conclude that targeting malaria by risk groups will not result in elimination as they constitute only a proportion parasite reservoir, therefore MDA might be necessary for rapid elimination.