9th International Conference on Plasmodium vivax Research (ICPvR) – 2025: Day 1

MESA Correspondents bring you cutting-edge coverage from the ICPvR 2025 “Plasmodium vivax: Science and tools for elimination”.

Registration and Inauguration 

The Indian Council of Medical Research (ICMR) – Vector Control Research Centre (VCRC), Puducherry hosted the 9th International Conference on Plasmodium vivax Research (ICPvR) 2025 at Trafalgar Square, Ocean Spray Resort, Puducherry, India. The conference brought together over 256 participants from around the world, including 120 international attendees. The conference’s theme was “Plasmodium vivax – Science and Tools for Elimination.” Opening remarks were delivered by several distinguished speakers: Manju Rahi (Convenor), Ashwani Kumar (Conference Chairperson), Amit Sharma (Co-Chairperson),  Rajani Ved (Guest of Honour), Rakesh Sehgal (Guest of Honour), Tanu Jain (Chief Guest), Rajiv Bahl (Director General, Indian Council of Medical Research) and Saima Wazed (Regional Director, World Health Organisation, South-East Asia). All speakers acknowledged the conference theme, emphasizing the significant challenges in different facets of malaria elimination and the urgent need for innovative tools to support national malaria elimination programs related to vivax malaria.

Session 1 – Keynote lecture and plenary sessions

Nick White (Mahidol University, Thailand)  discussed the geographical distribution, origin, and spread of Plasmodium vivax malaria. He highlighted the current diagnostic methods, their limits of detection, and the drawbacks associated with these modalities. White pointed out that severe vivax malaria (SVM) may result from overdiagnosis. In comparison to Plasmodium falciparum (P. falciparum) malaria, uncomplicated vivax malaria is characterized by lower parasite densities, reduced pyrogenic diversity, and greater red cell loss per parasitized erythrocyte. P. vivax malaria has a higher incidence in children and is more transmissible than P. falciparum malaria. The likelihood of disease progression to severe complications such as hepatic dysfunction, renal dysfunction, metabolic acidosis, severe thrombocytopenia, and cerebral dysfunction is much lower in P. vivax malaria than in P. falciparum malaria. Vivax malaria during pregnancy is linked to complications such as abortion and low birth weight. Additionally, the burden of asymptomatic malaria may represent the hidden extent of vivax malaria, often described as the “unseen iceberg”. White concluded by emphasizing that early detection and treatment are crucial for the elimination of malaria.

Dhanpat Kochar (Sardar Patel Medical College, India) emphasized key epidemiological changes in Plasmodium vivax malaria during global malaria elimination programs, noting a higher incidence of severe cases in India and Indonesia. He addressed the changes in the ratio of short-incubation P. vivax in temperate regions to long-incubation in sub-tropical and tropical areas. Kochar emphasized well-documented cases of severe P. vivax malaria since 2005, accompanied by consequences including cerebral malaria, convulsions, jaundice, renal failure, multiorgan dysfunction, and post-malarial neurological syndrome. Particularly, mortality from severe P. vivax was higher in children compared to adults. Thrombocytopenia was stressed as a significant yet currently unrecognized complication of severe malaria. Additional challenges in malaria elimination, such as sub-microscopic infections in pregnant women and Duffy-negative individuals were also underscored due to their role as hidden reservoirs contributing to persistent infections.

Kevin Baird (Oxford University Clinical Research Unit, Indonesia) challenged the belief that Plasmodium vivax causes only benign malaria. A clinical audit from Papua showed a case fatality rate of 0.022% for P. vivax, with severe cases occurring even in regions without P. falciparum. In South Korea, severe P. vivax infections occur despite good healthcare and nutrition, indicating the parasite alone can cause life-threatening illness. Baird emphasized that P. vivax has a strong tropism for extravascular erythropoietic tissues, including the bone marrow, spleen, and liver, making peripheral parasitaemia an unreliable indicator of severity. This hidden biomass correlates with severe disease, challenging conventional diagnostics. Baird also discussed that our current methods fail to detect P. vivax in deep organs, likely underestimating its burden. He added further the parasite’s preference for immature reticulocytes suggests stress erythropoiesis may expand its biomass dangerously. Until better diagnostic tools emerge, our understanding of P. vivax’s global impact remains incomplete, requiring a reassessment of its burden and consequences.

Session 2 – Unveiling Plasmodium vivax  dynamics: transmission, genomics & surveillance

Tanu Jain (National Centre for Vector Borne Diseases Control – NCVBDC, India) discussed India’s progress towards malaria elimination, along with other diseases like Kala Azar and Lymphatic Filariasis. She reviewed malaria elimination efforts from 2015 to 2023, addressing challenges in different categories. Jain presented the National Strategic Plan for Malaria Elimination (2023-2027), which emphasizes four key strategies: transforming surveillance, ensuring universal access to diagnosis and treatment, enhancing malaria control measures, and accelerating the path to malaria-free status, highlighting an 80.5% reduction in malaria cases and a 78.3% reduction in deaths. Jain also pointed out the challenges of controlling Plasmodium vivax malaria, with an 80% relapse rate due to the hypnozoite stage. She discussed diagnostic methods, including microscopy, rapid diagnostic tests (RDTs), and new tools like tafenoquine and G6PD testing. Jain also underscored the critical role of grassroots health workers in achieving malaria elimination.

Leanne Robinson (Burnet Institute, Australia) highlighted the global burden of Plasmodium vivax malaria, noting its dominance in the Asia-Pacific and South America. The hidden burden of P. vivax persists despite declining malaria cases, with 80% of infections resulting from relapses and many remaining undetectable due to current diagnostic limitations. As prevalence decreases, a growing proportion of infections become sub-patent, with 60-80% falling below the detection limits of microscopy and rapid diagnostic tests (RDTs), especially in low-transmission areas. To tackle P. vivax challenges, strategies include next-generation RDTs with fivefold improved sensitivity, G6PD-guided 7-day high-dose primaquine (PQ7) and tafenoquine (TQ) treatment for safe radical cure, and P. vivax serological testing and treatment (Pv SeroTAT) for detecting hypnozoite reservoirs. Studies like SCOPE, TRUST, ARCTIC, and EFFORT support policy-driven implementation, highlighting feasibility, cost-effectiveness, and public health benefits in co-endemic settings.

Harsha Kota (Indian Institute of Technology Delhi – IIT Delhi, India)  presented a study on the impact of climate change on malaria incidence, focusing on developing an accurate malaria forecast model for Goa, a historically endemic region with significant case reduction over the past decade. Using data from 2010–2019 from the National Centre for Vector Borne Diseases Control (NCVBDC) and ECMWF RE Analysis V5, temperature and precipitation variations in North and South Goa were analyzed. The study applied seasonal Mann-Kendall tests to identify strong climate trends and Pearson’s correlation to assess climate prediction accuracy. In forecasting, time series models like ARIMA and SARIMA, as well as machine learning models such as Support Vector Machine, Random Forest, and XGBoost, alongside hybrid models combining ARMA and machine learning methods, were used. The findings revealed that extreme weather events had a greater impact on malaria incidence than standard weather conditions. Kota emphasized that history-informed machine learning models performed best in forecasting malaria and highlighted the importance of integrating climate data into predictive models to improve malaria forecasting accuracy and strengthen proactive health measures.

Sanjay Kochar (Sardar Patel Medical College, India) presented a study from the Bikaner district, Rajasthan, India, investigating the influence of asymptomatic and submicroscopic Plasmodium vivax infections on elimination efforts. Out of 2,325 individuals tested for P. falciparum and P. vivax using rapid diagnostic tests (RDTs), 131 tested negative. Polymerase chain reaction (PCR) of these negative samples identified P. vivax in three cases, with no P. falciparum detected. Peripheral blood smear identified gametocytes in a single sample, necessitating a thorough examination of over 200 high-power fields. These findings highlight the limitations of the current diagnostic techniques in identifying low-density infections. Kochar concluded by emphasizing the need for improved diagnostic tools, enhanced surveillance, and targeted policy interventions. 

Session 3 – Rethinking Relapse: In vivo Studies & Human Challenge Models (1/2)

Jean Popovici (Institut Pasteur, Cambodia) presented a study investigating Plasmodium vivax relapses in Cambodia, focusing on hypnozoite regulation and reactivation. The study highlighted geographic variation in relapse timing, with 50% of relapses occurring within 4 weeks in Thailand and 60% in Cambodia. A clinical trial compared primaquine (PQ) doses of 3.5 mg/kg and 7.0 mg/kg over 14 days, revealing that a higher dose was necessary to prevent recurrence within 90 days. Popovici noted that no evidence of artesunate failure was observed, as recurrence clearance was as rapid as initial infections. Whole-genome sequencing (WGS) of P. vivax is ongoing to further investigate relapse mechanisms. The study also identified a consistent increase in reticulocyte count 13-14 days before relapse, suggesting a link between erythropoiesis and hypnozoite activation. These findings, Popovici explained, provide new insights into P. vivax relapse patterns and potential biomarkers, which may help refine treatment strategies and improve malaria control efforts.

Kavitha Saravu (Kasturba Medical College, India) discussed the clinical presentations of acute malaria and the challenges associated with differentiating P. vivax malaria from P. falciparum based solely on clinical features. She summarized the World Health Organization (WHO) criteria and various definitions for severe vivax malaria, accompanied by a case study highlighting severe vivax malaria. Key complications of malaria include cerebral malaria, renal failure, lung complications (such as ARDS), and severe anemia. Notably, more than 50% of cerebral vivax malaria cases and over 70% of renal manifestations have been reported from India. In a series of postmortem examinations of malaria cases, lung complications were found to be the most common findings. Saravu emphasized the urgent need for new definitions and criteria for vivax malaria in clinical practice. Additionally, she identified the prevention of vivax malaria and its potential relapses in children and pregnant women as a top priority.

Chetan Chitnis (Malaria Parasite Biology and Vaccines Unit, Institut Pasteur, France)  discussed P. vivax vaccine candidates and the current challenges. Chitnis emphasized the importance of erythrocyte-binding proteins. Specifically, sulfated Y41 plays a crucial role in the binding assay of P. vivax Duffy Binding Protein (PvDBP)-II with the Duffy antigen receptor for chemokines (DARC). In a trial examining the efficacy of the PvDBP II vaccine in protecting against P. vivax blood-stage challenges, a parasite multiplication rate (PMR) reduction of 53% was observed in volunteers who received the PvDBP II vaccine using a delayed dosing regimen of 0, 1, and 14 months. However, no significant impact was noted in the group that received the regimen of 0, 1, and 2 months. Other immune correlates: FcγR and C1q binding suggest that antibody-dependent cellular mechanisms and complement activation may also contribute to protection. 

Session 4 – Rethinking Relapse: In vivo Studies & Human Challenge Models (2/2)

Kamala Thriemer (Menzies School of Life Sciences, Australia) presented a study on Plasmodium vivax malaria relapse prevention in Ethiopia, Pakistan, Indonesia, and Cambodia. Patients received schizontocidal treatment with either high-dose primaquine (PQ7 – 7 mg/kg for 7 days), a single dose of tafenoquine (TQ), or low-dose primaquine (PQ14 – 3.5 mg/kg for 14 days), all unsupervised. PQ7 and TQ were more effective than PQ14 over six months. TQ was effective with chloroquine in Pakistan and Ethiopia, artesunate-pyronaridine in Cambodia, and DHA-piperaquine in Indonesia. No hemolysis occurred with PQ7 or TQ in patients with >70% G6PD activity, ensuring safety and tolerability.

Maria Ome-Kaius (Papua New Guinea  Institute of Medical Research – PNG IMR, Papua New Guinea) presented the SCOPE study aimed at evaluating the feasibility of point-of-care G6PD testing combined with a short course of PQ for the radical treatment of P. vivax malaria. The study is divided into two stages. In Stage 1, a safety review of PQ treatment was conducted at two clinics in Indonesia and two in PNG. Stage 2 will assess the feasibility and cost-effectiveness of the intervention at 6 clinics in Indonesia and 4 clinics in PNG, scheduled for 2025. The rates of adverse events of special interest (AESI) and serious adverse events (SAE) were generally lower than those reported in previous PQ clinical trials as well as the overall risk of hospitalization. She concluded that findings from both stages will help inform Ministry of Health consultations on updating vivax malaria guidelines and scaling up interventions.

Rintis Noviyanti (Eijkman Research Centre for Molecular Biology, Indonesia) presented a study assessing a newly developed microhaplotype assay on samples from a therapeutic efficacy study conducted in Timika, PNG, a region with high malaria transmission. Noviyanti explained that the assay generates identity by descent (IBD) values, which quantify the proportion of shared DNA fragments between parasites. An IBD of 100% indicates a clonal relationship, 50% suggests sibling parasites and 25% corresponds to half-siblings. Among 84 analyzed samples, the study identified one case with approximately 100% IBD, likely representing a relapse, and another with ~6.25% IBD, suggesting a possible reinfection. These findings highlight the utility of microhaplotype assays in distinguishing relapse from reinfection, contributing to more precise malaria surveillance and control strategies.

Madan Mohan (Vector Borne Diseases, Health & Family Welfare Department, India) presented recent trends in P. vivax malaria and the challenges associated with it in a district predominantly affected by P. falciparum malaria. Secondary epidemiological data from routine malaria surveillance and the Durgama Anchalare Malaria Nirakaran (DAMaN) system were collected and analyzed. In certain P. falciparum-dominated sub-centers under the DAMaN Mass Screening and Treatment initiative, P. vivax cases surged to over 90% in 2024. By September 2024, the overall incidence of malaria had risen fivefold, with 1,841 cases reported compared to just 349 cases in 2023. To address this unprecedented P. vivax increase in the P. falciparum-endemic regions, new approaches such as TrueNatⓇ could be considered for detecting sub-microscopic P. vivax malaria at the primary healthcare level. Additionally, administering a single dose of TQ for a radical cure may be beneficial for the national malaria program.

Pubudu Chulasiri (Ministry of Health, Sri Lanka) studied imported P. vivax cases from 2013 to 2023, documenting, treating, and monitoring them for relapses over a 12-month period. His analysis showed that P. vivax accounted for 40.5% of imported malaria cases, with its proportion decreasing from 54.7% in 2013 to 6.45% in 2023, likely reflecting India’s declining malaria burden. Despite effective treatment, three cases experienced relapses, indicating a delayed illness onset compared to P. falciparum. Chulasiri also noted the higher prevalence of P. vivax gametocytes, which increases transmission potential and poses a greater risk of re-establishment than P. falciparum. These findings highlight the challenges in eliminating P. vivax, particularly in regions receiving imported cases. They also reinforce the importance of continued surveillance, effective relapse prevention, and international collaboration to prevent resurgence in malaria-free areas.

Stephanie Zobrist (Diagnostics – PATH, United States) presented a study that assessed the STANDAR G6PD test for identifying severe anaemia in malaria case management. The STANDARD test was conducted on capillary specimens, alongside a comparator point-of-care hemoglobin test: the HemoCue 201+ (HemoCue AB, Sweden). A total of 951 participants were enrolled, 466 with available test results. Nearly one-quarter (24%) of the participants had moderate or severe anemia. When compared to the reference complete blood count (CBC) assay, the STANDARD G6PD test showed similar performance and patterns of misclassification as the HemoCue, when used in a controlled clinical evaluation. No true cases of severe anaemia were misclassified by the STANDARD Test but it tended to overestimate moderate and severe anaemia. HemoCue misclassified two severe anemia cases as moderate but showed a higher overall positive predictive value (PPV) for severe anemia. The STANDARD G6PD test reliably identifies severe cases. Zobrist emphasized its importance in remote areas with limited assessment options.