A role for super-spreaders in carrying malaria parasites across the months-long dry season

In malaria endemic regions, transmission of Plasmodium falciparum parasites is often seasonal with very low transmission during the dry season and high transmission in the wet season. Parasites survive the dry season within some individuals who experience prolonged carriage of parasites and are thought to ‘seed’ infection in the next transmission season. We use a combination of mathematical simulations and data analysis to characterise dry season carriers and their role in the subsequent transmission season. Simulating the life-history of individuals experiencing repeated exposure to infection predicts that dry season carriage is more likely in the oldest, most exposed and most immune individuals. This hypothesis is supported by data from a longitudinal study in Mali that shows that carriers are significantly older, experience a higher biting rate at the beginning of the transmission season and develop clinical malaria later than non-carriers. Further, since the most exposed individuals in a community are most likely to be dry season carriers, we show that this is predicted to enable a more than 2-fold faster spread of parasites into the mosquito population at the start of the subsequent wet season. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by the Australian Research Council (ARC) (grant DP120100064 & DP180103875 (to DSK, MPD) and the National Health and Medical Research Council (NHMRC) of Australia (grants 1082022 (to MPD), 1141921 (to DSK), and 1080001 and 1173027 (to MPD). The cohort study in Mali was funded by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, with intramural grants to PDC. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The ethics committee of the Faculty of Medicine, Pharmacy and Dentistry at the University of Sciences, Techniques and Technology of Bamako, and the Institutional Review Board of NIAID NIH approved the study (ClinicalTrials.gov [NCT01322581][1]). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The data and code are available upon request. The data and code are available upon request. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT01322581&atom=%2Fmedrxiv%2Fearly%2F2022%2F05%2F02%2F2022.04.28.22274398.atom