Plasmodium vivax genotyping and modelling: a new tool for malaria control in Central Vietnam

Plasmodium vivax is the most widely spread ofthe four malaria species and the main cause of malaria outside Sub-Sahara Africa. In Central Vietnam, nearly 50% of malaria infections are due to P. vivax, causing a heavy morbidity burden for the local population due to the activation (relapse) of dormant liver forms (hypnozoites) weeks or months after the primary infection. The national guidelines for the radical cure of P. vivax infection was changed in 2007, with an increase of the daily dose of primaquine from 0.25mg/kg to 0.50mglkg for 10 days (the 3-day concomitant chloroquine regimen (total 25mglkg) remaining unchanged). The efficacy of this new regimen in preventing short as well as long term relapses has not been evaluated yet. Moreover, the epidemiology and the transmission dynamics of P. vivax remains poorly documented due to the lack of reliable tools to distinguish between new infections, recrudescence and relapses. Consequently, as control strategies cannot be adequately adapted to the local epidemiology, P. vivax morbidity continues to contribute to the vulnerability of the local populations, mainly ethnic minorities, with poor health and socio economic status. The main objective of this study is to establish a new tool that will assist the National Malaria Control Program to improve control strategies for P. vivax in Vietnam. This tool will be based on molecular (microsatellites) and serological (CSP ELISA) techniques and on mathematical modelling, to distinguish between a new infection, and a relapse/recrudescence of P. vivax. A cohort of 300 P. vivax infected patients will be treated and followed up for 2 years in order to estimate the efficacy of the current treatment guideline in preventing recrudescence and relapses, and determine the incidence of new infections. The development of such a tool is extremely important for the control of P. vivax in Vietnam since f) \ .. it will help to understand the epidemiology of P. vivax and to test targeted interventions, including new drugs. Eventually, the National Malaria Control Program will be able to adapt its control strategies and monitor the efficacy of the treatment guidelines. 5

Trefwoorden:B780-tropische-geneeskunde