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Item does not contain fulltext, Malaria transmission depends on the presence of Plasmodium gametocytes that are the only parasite life stage that can infect mosquitoes. Gametocyte production varies between infections and over the course of infections. Infection duration is highly important for gametocyte production but poorly quantified. Between 2017 and 2019 an all-age cohort of individuals from Tororo, eastern Uganda was followed by continuous passive and routine assessments. We longitudinally monitored 104 incident infections from 98 individuals who were sampled once every 28 days and on any day of symptoms. Among infections that lasted ≥ 3 months, gametocyte appearance was near-universal with 96% of infections having detectable gametocytes prior to clearance. However, most infections were of much shorter duration; 55.7% of asymptomatic infections were detected only once. When considering all asymptomatic infections, regardless of their duration, only 36.3% had detectable gametocytes on at least one time-point prior to parasite clearance. Infections in individuals with sickle-cell trait (HbAS) were more likely to have gametocytes detected (Hazard Rate (HR) = 2.68, 95% CI 1.12, 6.38; p = 0.0231) and had gametocytes detected at higher densities (Density Ratio (DR) = 9.19, 95% CI 2.79, 30.23; p = 0.0002) compared to infections in wildtype (HbAA) individuals. Our findings suggest that a large proportion of incident infections is too short in duration and of too low density to contribute to onward transmission.

Item does not contain fulltext

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Contains fulltext : 239987.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 226783.pdf (Publisher’s version ) (Open Access)

Contains fulltext : 172114.pdf (publisher's version ) (Open Access), BACKGROUND: Parasite prevalence is a key metric used to quantify the burden of malaria and assess the impact of control strategies. Most published estimates of parasite prevalence are based on microscopy and likely underestimate true prevalence. METHODS: Thick smear microscopy was performed in cohorts of children (aged 6 month to 10 years) and adults every 90 days over 2 years, at three sites of varying transmission intensity in Uganda. Microscopy-negative samples were tested for sub-microscopic parasitaemia using loop-mediated isothermal amplification (LAMP). Generalized estimating equation models were used to evaluate associations between age and parasitaemia, factors associated with sub-microscopic infection and associations between parasitaemia and haemoglobin. RESULTS: A total of 9260 samples were collected from 1245 participants. Parasite prevalence among children across the three sites was 7.4, 9.4 and 28.8 % by microscopy and 21.3, 31.8 and 69.0 % by microscopy plus LAMP. Parasite prevalence among adults across the three sites was 3.1, 3.0 and 5.2 % by microscopy and 18.8, 24.2 and 53.5 % by microscopy plus LAMP. Among those with parasitaemia, adults and persons recently treated with anti-malarial therapy had the highest prevalence of sub-microscopic infection. Children with sub-microscopic or microscopic parasitaemia had lower mean haemoglobin levels compared to children with no detectable parasites. CONCLUSIONS: Across a range of transmission intensities in Uganda, microscopy vastly underestimated parasite prevalence, especially among adults.

Contains fulltext : 138121.pdf (publisher's version ) (Open Access), Glucose-6-phosphate dehydrogenase (G6PD) enzyme function and genotype were determined in Ugandan children with uncomplicated falciparum malaria enrolled in a primaquine trial after exclusion of severe G6PD deficiency by fluorescent spot test. G6PD A- heterozygotes and hemizygotes/homozygotes experienced dose-dependent lower hemoglobin concentrations after treatment. No severe anemia was observed.

Contains fulltext : 136831.pdf (publisher's version ) (Open Access)

Contains fulltext : 117695.pdf (publisher's version ) (Open Access), OBJECTIVES: For the purpose of blocking transmission of Plasmodium falciparum malaria from humans to mosquitoes, a single dose of primaquine is recommended by the WHO as an addition to artemisinin combination therapy. Primaquine clears gametocytes but causes dose-dependent haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Evidence is needed to inform the optimal dosing of primaquine for malaria elimination programmes and for the purpose of interrupting the spread of artemisinin-resistant malaria. This study investigates the efficacy and safety of reducing doses of primaquine for clearance of gametocytes in participants with normal G6PD status. METHODS AND ANALYSIS: In this prospective, four-armed randomised placebo-controlled double-blinded trial, children aged 1-10 years, weighing over 10 kg, with haemoglobin >/=8 g/dl and uncomplicated P falciparum malaria are treated with artemether lumefantrine and randomised to receive a dose of primaquine (0.1, 0.4 or 0.75 mg base/kg) or placebo on the third day of treatment. Participants are followed up for 28 days. Gametocytaemia is measured by quantitative nucleic acid sequence-based analysis on days 0, 2, 3, 7, 10 and 14 with a primary endpoint of the number of days to gametocyte clearance in each treatment arm and secondarily the area under the curve of gametocyte density over time. Analysis is for non-inferiority of efficacy compared to the reference dose, 0.75 mg base/kg. Safety is assessed by pair-wise comparisons of the arithmetic mean (+/-SD) change in haemoglobin concentration per treatment arm and analysed for superiority to placebo and incidence of adverse events. Ethics and dissemination Approval was obtained from the ethical committees of Makerere University School of Medicine, the Ugandan National Council of Science and Technology and the London School of Hygiene and Tropical Medicine. RESULTS: These will be disseminated to inform malaria elimination policy, through peer-review