Sources of persistent malaria transmission in a setting with effective malaria control in eastern Uganda: a longitudinal, observational cohort study

Abstract

Background Symptomatic malaria cases reflect only a small proportion of all Plasmodium spp infections. Many infected individuals are asymptomatic, and persistent asymptomatic Plasmodium falciparum infections are common in endemic settings. We aimed to quantify the contribution of symptomatic and asymptomatic infections to P falciparum transmission in Tororo, Uganda.Methods We did a longitudinal, observational cohort study in Tororo district, Uganda. We recruited participants of all ages from randomly selected households within this district. Participants were eligible if the selected household had no more than nine permanent residents and at least two members younger than 10 years, and the household was their primary residence, and they agreed to come to the study clinic for any fever episode and avoid antimalarial medications outside the study. Participants were followed-up by continuous passive surveillance for the incidence of symptomatic infections; routine assessments (ie, standardised clinical evaluation and blood samples) were done at baseline and at routine visits every 4 weeks for 2 years. P falciparum parasite density, gametocyte density, and genetic composition were determined molecularly using quantitative PCR (qPCR), quantitative reverse transcriptase PCR (qRT-PCR), and amplicon deep sequencing, respectively. Membrane feeding assays were also done to assess infectivity to mosquitoes. The contribution of different populations to the infectious reservoir was estimated for symptomatic infections, asymptomatic but microscopically detected infections, and asymptomatic but qPCR-detected infections; and for age groups younger than 5 years, 5-15 years, and 16 years or older.

Current malaria infection, previous malaria exposure, and clinical profiles and outcomes of COVID-19 in a setting of high malaria transmission: an exploratory cohort study in Uganda

“…The prevalence of malaria in this cohort is similar to population-level regional estimates in the country, as shown by studies that used molecular methods for malaria diagnosis. 25 However, although malaria-disease burden in malaria-endemic settings such as Uganda is largely concentrated in infants and young children, the substantial burden of P falciparum infection among patients with COVID-19 who were older than 60 years of age in this study is intriguing and requires further investigation.…”

‘Bouncing Back’ From Subclinical Malaria: Inflammation and Erythrocytosis After Resolution of P. falciparum Infection in Gambian Children

“…It is difficult to completely exclude the possibility of current or very recent malaria infection in children living in endemic areas. The presence of PCR detectable parasites may vary from day to day over weeks or months of follow up in individual children (40,41). Children can maintain the same (genetically identical) parasite infection for many months with parasites only being intermittently detectable by microscopy and PCR (41,42) and the density of subclinical infections can vary through time with windows of undetectable parasitaemia (41).…”

“…The presence of PCR detectable parasites may vary from day to day over weeks or months of follow up in individual children (40,41). Children can maintain the same (genetically identical) parasite infection for many months with parasites only being intermittently detectable by microscopy and PCR (41,42) and the density of subclinical infections can vary through time with windows of undetectable parasitaemia (41). Moreover, a recent study has revealed a hidden biomass of parasites in the spleens of patients undergoing splenectomy, including some patients in whom no circulating parasites could be detected (43).…”

Risk of Plasmodium falciparum infection in south-west Burkina Faso: potential impact of expanding eligibility for seasonal malaria chemoprevention

“…The review found intermittent preventive treatment to be well tolerated and acceptable to communities. School-aged children are significant reservoirs of human-to-mosquito transmission 35 – 37 . There is some evidence that administration of intermittent preventive treatment to school-age children can confer a community-level benefit to those not receiving intermittent preventive treatment.…”