Science Bite (3 minute oral presentation with PPT in live session and poster) - Students, ECRs and EMCRs only 15th Lorne Infection and Immunity 2025

Identifying the sources of Plasmodium falciparum infections following intensive control efforts in malaria endemic PNG (#330)

Sonakshi Madan 1 , Kirsty McCann 1 2 , Zahra Razook 1 2 , Dulcie Lautu-Gumal 1 2 3 4 , Shazia Ruybal-Pesantez 3 4 5 , Benson Kiniboro 6 , Peter M Siba 6 , Stephan Karl 7 , Maria Ome-Kaius 6 , Moses Laman 6 , James W Kazura 8 , Ivo Mueller 3 4 , Leanne J Robinson 2 3 6 , Alyssa E Barry 1 2 3
  1. Centre for Innovation in Infectious Disease and Immunology Research, IMPACT and School of Medicine, Deakin University, Geelong, Victoria, AUSTRALIA
  2. Life Sciences Discipline, Burnet Institute, Melbourne, Victoria, AUSTRALIA
  3. Population Health and Immunity Division, Walter and Eliza Hall Institute, Parkville, Melbourne, Victoria, AUSTRALIA
  4. Department of Medical Biology, University of Melbourne, Parkville, Melbourne, Victoria, AUSTRALIA
  5. MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, UNITED KINGDOM
  6. Vector Borne Diseases Unit, Papua New Guinea Institute of Medical Research, Madang, PAPUA NEW GUINEA
  7. Australian Institute of Health and Tropical Medicine, James Cook University, Cairns, Queensland, AUSTRALIA
  8. Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, USA

Malaria transmission has been significantly reduced through the past decades via intensive, multifaceted control efforts. However, challenges to elimination remain in the form of residual asymptomatic and imported infections increasing the risk of resurgence. Declining transmission limits genetic recombination in circulating parasites, leading to fragmented parasite population structure. Human populations are then exposed to fewer, possibly only local circulating parasites, which potentially limits naturally acquired immunity to these strains. Consequently, this may increase host susceptibility to clinical symptoms if infected with introduced strains. Additionally, asymptomatic infections appear more prevalent in low-transmission regions and often undetected, serve as reservoirs for ongoing transmission. The interplay between decreasing transmission, parasite diversity, and host immunity may contribute to prevalence of asymptomatic and symptomatic infections. Papua New Guinea (PNG), historically a region of high malaria transmission, recorded substantial transmission decline (2012) followed by resurgence of infection (2016), providing an opportunity to evaluate parasite population structure and sources of resurgence at low-transmission. Utilizing asymptomatic isolates from cross-sectional surveys in East Sepik, PNG in 2012 and 2016, and clinical isolates from a therapeutic efficacy study in 2012, we assessed Plasmodium falciparum strain diversity and investigated the association between parasite genetics and symptomatic malaria   in 2012, and resurgent lineages in 2016. P. falciparum infections were compared using SNP barcoding and ‘varcoding’ of the var genes encoding the major surface antigen to evaluate parasite diversity, relatedness, population structure and antigenic diversity. Clustering (PCA), nucleotide diversity (Hierfstat), pairwise relatedness (IsoRelate) and logistic regression were used to identify origins of infections, transmission chains, links between infections and strain diversity, proportion of imported and local strains, and its variation with transmission levels. These results aim to fill a crucial knowledge gap regarding sources of infections in 2012 and resurgent cases in 2016, contributing to improved surveillance and outbreak prediction in malaria-endemic regions.