Higher gametocyte production and mosquito infectivity in chronic compared to incident Plasmodium falciparum infections
Aïssata Barry, John Bradley, William J. Stone, Wamdaogo M. Guelbéogo, Kjerstin Lanke, Alphonse Ouédraogo, Issiaka Soulama, Issa Nébié, Samuel Sindié Sermé, Lynn Grignard, Catriona Patterson, Lindsey Wu, Jessica Briggs, Owen Janson, Shehu Shagari Awandu, Mireille Ouédraogo, Casimire Wendlamita Tarama, Désiré Kargougou, Soumanaba Zongo, Sodiomon B. Sirima, Matthias Marti, Chris Drakeley, Alfred B. Tiono, Teun Bousema
Abstract
Plasmodium falciparum gametocyte kinetics and infectivity may differ between chronic and incident infections. In the current study, we assess parasite kinetics and infectivity to mosquitoes among children (aged 5-10 years) from Burkina Faso with (a) incident infections following parasite clearance (n = 48) and (b) chronic asymptomatic infections (n = 60). In the incident infection cohort, 92% (44/48) of children develop symptoms within 35 days, compared to 23% (14/60) in the chronic cohort. All individuals with chronic infection carried gametocytes or developed them during follow-up, whereas only 35% (17/48) in the incident cohort produce gametocytes before becoming symptomatic and receiving treatment. Parasite multiplication rate (PMR) and the relative abundance of ap2-g and gexp-5 transcripts are positively associated with gametocyte production. Antibody responses are higher and PMR lower in chronic infections. The presence of symptoms and sexual stage immune responses are associated with reductions in gametocyte infectivity to mosquitoes. We observe that most incident infections require treatment before the density of mature gametocytes is sufficient to infect mosquitoes. In contrast, chronic, asymptomatic infections represent a significant source of mosquito infections. Our observations support the notion that malaria transmission reduction may be expedited by enhanced case management, involving both symptom-screening and infection detection.