Efficacies of 5-and 14-day primaquine regimens in the prevention of relapses in Plasmodium vivax infections

Vivax malaria accounts for 80% of malaria cases in Mumbai (Bombay) and has high morbidity. In India, the standard treatment to prevent relapses of viv ax malaria is a 5-day regimen of primaquine. However, between 1977 and 1997 , the efficacy of this treatment declined from approximately 99% to 87%. Th e efficacy of the 5-day regimen was therefore compared with that of the 14- day regimen currently recommended by the World Health Organization, in Mumb ai. The relapse rates observed, over a 6-month period of follow-up, were 0% with the 14-day regimen, 26.7% with the 5-day, and 11.7% when no primaquin e treatment was given. The expenditure incurred on the door-to-door dispensing of the 5-day regime n appears to be without benefit. There is an urgent need to review the pres ent strategy for controlling relapses in vivax malaria, at least for the ci ty of Mumbai, and similar studies need to be carried out in other parts of India, to make all anti-relapse strategies more appropriate.