Plasmodium vivax Malaria Relapse Risk Depends on Transmission Intensity: Evidence From a Longitudinal Study in Northwest Thailand
Issued Date
2026-01-01
Resource Type
eISSN
23288957
Scopus ID
2-s2.0-105028023166
Journal Title
Open Forum Infectious Diseases
Volume
13
Issue
1
Rights Holder(s)
SCOPUS
Bibliographic Citation
Open Forum Infectious Diseases Vol.13 No.1 (2026)
Suggested Citation
Chu C.S., Lwin K.M., Burgoine K., Phyo A.P., Turner C., San T., Aung A.A., Win H.H., Htoo K., Soe N.L., Christina N., Than H.H., Dah N., Pilaseng K., Wiladpaingern J., Proux S., Mukaka M., Parker D.M., Carrara V.I., Nosten F., White N.J. Plasmodium vivax Malaria Relapse Risk Depends on Transmission Intensity: Evidence From a Longitudinal Study in Northwest Thailand. Open Forum Infectious Diseases Vol.13 No.1 (2026). doi:10.1093/ofid/ofaf667 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/114666
Title
Plasmodium vivax Malaria Relapse Risk Depends on Transmission Intensity: Evidence From a Longitudinal Study in Northwest Thailand
Corresponding Author(s)
Other Contributor(s)
Abstract
Background In northwest Thailand, the provision of radical cure to prevent relapses of Plasmodium vivax malaria has decreased P vivax caseloads and decreased transmission. While malaria control measures were increased, we performed a prospective observational rolling cohort study to describe the changing incidence of P vivax malaria and the associated recurrence rates. Methods Healthy nonpregnant glucose-6-phosphate dehydrogenase–normal volunteers who had symptomatic P vivax infection in the previous 12–24 months, but who had not received radical cure, were recruited. Supervised primaquine was given daily for 14 days (0.5 mg base/kg/day). Participants were followed 4 and 8 weeks later, then every 2 months until they developed symptomatic or asymptomatic P vivax malaria. Consultation for febrile illnesses was encouraged between follow-up visits. Participants who developed P vivax malaria were replaced with matched volunteers to maintain a continuous cohort of 200 participants. Results From March 2010 until September 2014, 380 healthy adults and children were enrolled. Ninety-two individuals developed P vivax malaria, 25 within 4 months of enrollment. The annual incidence of P vivax malaria infection decreased from 0.19 in 2010 to 0.09 infections per person-year in 2014. The primaquine failure rate (P vivax malaria within 4 months of treatment) was 75% less than predicted based on earlier assessments that assumed a constant hypnozoite reservoir. Conclusions Declining P vivax transmission reduces the hypnozoite reservoir in the population and the hypnozoite burden in an individual. This increases the apparent efficacy of radical cure in preelimination settings.