Data from: Within-host competition and drug resistance in the human malaria parasite Plasmodium falciparum
Bushman, Mary et al. (2016), Data from: Within-host competition and drug resistance in the human malaria parasite Plasmodium falciparum, Dryad, Dataset, https://doi.org/10.5061/dryad.qb814
Infections with the malaria parasite Plasmodium falciparum typically comprise multiple strains, especially in high-transmission areas where infectious mosquito bites occur frequently. However, little is known about the dynamics of mixed-strain infections, particularly whether strains sharing a host compete or grow independently. Competition between drug-sensitive and drug-resistant strains, if it occurs, could be a crucial determinant of the spread of resistance. We analyzed 1,341 P. falciparum infections in children from Angola, Ghana, and Tanzania and found compelling evidence for competition in mixed-strain infections: overall parasite density did not increase with additional strains, and densities of individual strains (chloroquine-sensitive and chloroquine-resistant) were reduced in the presence of competitors. We also found that chloroquine-resistant strains exhibited low densities compared to chloroquine-sensitive strains (in the absence of chloroquine), which may underlie observed declines of chloroquine resistance in many countries following retirement of chloroquine as a first-line therapy. Our observations support a key role for within-host competition in the evolution of drug-resistant malaria. Malaria control and resistance-management efforts in high-transmission regions may be significantly aided, or hindered, by the effects of competition in mixed-strain infections. Consideration of within-host dynamics may spur development of novel strategies to minimize resistance while maximizing the benefits of control measures.