Submicroscopic Plasmodium infections are an important parasite reservoir, but their clinical relevance is poorly defined. A cross-sectional household survey was conducted in southern Papua, Indonesia, using cluster random sampling. Data were recorded using a standardized questionnaire. Blood samples were collected for haemoglobin measurement. Plasmodium parasitaemia was determined by blood film microscopy and PCR. Between April and July 2013, 800 households and 2,830 individuals were surveyed. Peripheral parasitaemia was detected in 37.7% (968/2,567) of individuals, 36.8% (357) of whom were identified by blood film examination. Overall the prevalence of P. falciparum parasitaemia was 15.4% (396/2567) and that of P. vivax 18.3% (471/2567). In parasitaemic individuals, submicroscopic infection was significantly more likely in adults (adjusted odds ratio (AOR): 3.82 [95%CI: 2.49–5.86], p<0.001) compared to children, females (AOR = 1.41 [1.07–1.86], p = 0.013), individuals not sleeping under a bednet (AOR = 1.4 [1.0–1.8], p = 0.035), and being afebrile (AOR = 3.2 [1.49–6.93], p = 0.003). The risk of anaemia (according to WHO guidelines) was 32.8% and significantly increased in those with asymptomatic parasitaemia (AOR 2.9 [95% 2.1–4.0], p = 0.007), and submicroscopic P. falciparum infections (AOR 2.5 [95% 1.7–3.6], p = 0.002). Asymptomatic and submicroscopic infections in this area co-endemic for P. falciparum and P. vivax constitute two thirds of detectable parasitaemia and are associated with a high risk of anaemia. Novel public health strategies are needed to detect and eliminate these parasite reservoirs, for the benefit both of the patient and the community.

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Background Malaria control activities can have a disproportionately greater impact on Plasmodium falciparum than on P . vivax in areas where both species are coendemic. We investigated temporal trends in malaria-related morbidity and mortality in Papua, Indonesia, before and after introduction of a universal, artemisinin-based antimalarial treatment strategy for all Plasmodium species. Methods and findings A prospective, district-wide malariometric surveillance system was established in April 2004 to record all cases of malaria at community clinics and the regional hospital and maintained until December 2013. In March 2006, antimalarial treatment policy was changed to artemisinin combination therapy for uncomplicated malaria and intravenous artesunate for severe malaria due to any Plasmodium species. Over the study period, a total of 418,238 patients presented to the surveillance facilities with malaria. The proportion of patients with malaria requiring admission to hospital fell from 26.9% (7,745/28,789) in the pre–policy change period (April 2004 to March 2006) to 14.0% (4,786/34,117) in the late transition period (April 2008 to December 2009), a difference of −12.9% (95% confidence interval [CI] −13.5% to −12.2%). There was a significant fall in the mortality of patients presenting to the hospital with P . falciparum malaria (0.53% [100/18,965] versus 0.32% [57/17,691]; difference = −0.21% [95% CI −0.34 to −0.07]) but not in patients with P . vivax malaria (0.28% [21/7,545] versus 0.23% [28/12,397]; difference = −0.05% [95% CI −0.20 to 0.09]). Between the same periods, the overall proportion of malaria due to P . vivax rose from 44.1% (30,444/69,098) to 53.3% (29,934/56,125) in the community clinics and from 32.4% (9,325/28,789) to 44.1% (15,035/34,117) at the hospital. After controlling for population growth and changes in treatment-seeking behaviour, the incidence of P . falciparum malaria fell from 511 to 249 per 1,000 person-years (py) (incidence rate ratio [IRR] = 0.49 [95% CI 0.48–0.49]), whereas the incidence of P . vivax malaria fell from 331 to 239 per 1,000 py (IRR = 0.72 [95% CI 0.71–0.73]). The main limitations of our study were possible confounding from changes in healthcare provision, a growing population, and significant shifts in treatment-seeking behaviour following implementation of a new antimalarial policy. Conclusions In this area with high levels of antimalarial drug resistance, adoption of a universal policy of efficacious artemisinin-based therapy for malaria infections due to any Plasmodium ...

Background There is a high risk of Plasmodium vivax recurrence in patients treated for Plasmodium falciparum malaria in co-endemic areas. Primaquine radical cure has the potential to reduce P vivax recurrences in patients presenting with P falciparum as well as P vivax malaria but is undermined by poor adherence to the currently recommended 14-day regimen. We aimed to assess the efficacy and safety of supervised versus unsupervised primaquine radical cure in patients presenting with uncomplicated malaria.Methods We did a cluster-randomised, controlled, open-label superiority trial in Papua, Indonesia. 21 clusters of village health posts, matched by annual parasite index, were randomly assigned (1:1) to treat patients (age >12 months and body weight >5 kg) presenting with confirmed uncomplicated P falciparum or P vivax malaria with oral dihydroartemisinin-piperaquine plus either a supervised or unsupervised 14-day course of oral primaquine (0•5 mg/kg per day). Patients in the supervised group were supervised taking their primaquine dose on alternate days. Patients were followed-up for 6 months and those who presented again with malaria were retreated with the same drug regimen. Masking was not possible due to the nature of the study. The primary outcome was the incidence risk of P vivax malaria over 6 months, assessed in the modified intention-to-treat population (all patients who were assigned to a treatment group, excluding patients who were lost to follow-up after their first visit). This trial is now complete, and is registered with ClinicalTrials.gov, NCT02787070.