Studies to provide recommendations on the pre-elimination of Plasmodium vivax in Lao PDR

Malaria remains a major public health problem in malaria endemic countries despite a global reduction in the burden of the disease over the last two decades. The malaria control program has been threatened with the emergence and spread of multidrug resistant P. falciparum across the Greater Mekong Subregion (GMS). To achieve the goal of malaria elimination by 2030, mass drug administration with three monthly rounds of 3 day course of dihydroartemisinin-piperaquine plus single dose of primaquine was assessed in the four countries of GMS including Lao PDR. This thesis shows that asymptomatic malaria infections are prevalent in Lao PDR. Mass drug administration with the aim to eliminate P. falciparum was safe, feasible and acceptable by community in the Lao context with a significant reduction of P. falciparum for at least one year follow-up. However, it had a transient impact on P. vivax infections with the rebound in prevalence by month 6. A single low dose of primaquine used in MDA is to clear P. falciparum gametocytes but has no effect on the hypnozoites of P. vivax. MDA to eliminate all malarias should include both schizontocaidal and hypnozoitocidal drugs. A subset study to assess the efficacy of 14 day primaquine following three rounds of MDA in the prevention of recurrent of P. vivax infections showed that the strategy was safe and effective in the prevention of recurrence of asymptomatic P. vivax infections.