| Popis: |
The diversity ofPlasmodium falciparumwithin human hosts requires parasite population size be defined in terms of parasite variation rather than the number of infected hosts. To calculate census population size, we rely on a definition of parasite variation known as multiplicity of infection (MOIvar), defined by the hyper-diversity of thevarmultigene family. We present a Bayesian approach to estimate MOIvarbased on sequencing and counting the number of unique DBLα tags (or DBLα types) ofvargenes, taking into consideration measurement error, and derive from it census population size or the total number of distinct infections of relevance to transmission events. We track changes in parasite population size and structure, using MOIvar, from baseline and through sequential malaria interventions by indoor residual spraying (IRS) and seasonal malaria chemoprevention (SMC) in an area characterized by high-seasonal malaria transmission in northern Ghana.VarDBLα tag sequencing was completed on asymptomaticP. falciparumisolates at baseline (2012), during IRS (2014), post-IRS (2015) and during SMC (2017) from ∼2,000 individuals of all ages surveyed at each time point. Following IRS, which reduced transmission intensity by > 90% and decreased parasite prevalence by ∼40-50%, significant reductions invardiversity, MOIvar, and population size were observed across all ages. These changes, consistent with the loss of diverse parasite genomes, were short lived and 32-months after IRS was discontinued and SMC was introduced,vardiversity and population size rebounded in all age groups except for the younger children (1-5 years) targeted by SMC. By measuring population size in this way, we show that despite major perturbations, the parasite population remained very large and retained thevarpopulation genetic characteristics of a high-transmission system (highvardiversity; lowvarrepertoire similarity) demonstrating the resilience ofP. falciparumto short-term interventions in high-burden countries of sub-Saharan Africa. |
