Authors

A A GadallaP Schneider¹; T Churche²; E NassirA Abdel-MuhsinL Ranford-Cartwright³; S Reece¹; H Babiker ¹ Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh;  ² Department of Infectious Disease Epidemiology, Imperial College London;  ³ Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow;  ⁴ Khartoum University, Sudan;  ⁵ Sultan Qaboos University , Oman;  ⁶ Tropical Medicine Research Institute, Sudan

Discussion

In areas of seasonal malaria, asymptomatic P. falciparum infections can persists during the transmission-free period and raise new cases following the start of annual rains. However the impact of season and carriage of drug resistance alleles on transmission of such infections, is yet unknown. A cohort with symptomatic P. falciparum infections were recruited and treated during the transmission season. Participants who maintained asymptomatic infections after treatment were then monitored monthly throughout distinct dry and wet seasons (12 months). Parasite and gametocyte densities were measured using qPCR and RT-qPCR, respectively. Drug resistance genes pfcrt and pfmdr1 were genotyped and within-host relative abundance wild-genotypes was determined using qPCR.
Results revealed enhanced investment in gametocyte production at the start of the rainy season, and prior to the peak of clinical cases. Wild-genotypes overgrew the mutant genotypes of drug resistance genes during therapy-free period. However, mutant genotype of pfcrt was associated with higher gametocyte densities, with no effect of season on the association. 
These findings highlight the need for season-adjusted control measures and implementation of control and elimination strategies that do not enhance selection of drug resistant alleles during the dry season.