Resistance among malaria parasites in Africa to a widely used drug is due to 'migration' of resistant parasites from South-East Asia, according to research published in Science. The study, led by Cally Roper of the UK London School of Hygiene and Tropical Medicine, compared the genetic makeup of malaria parasites from South-East Asia and Africa. Its results suggest that parasites resistant to sulfadoxine pyrimethamine (SP) originally arrived in Africa from South-East Asia, where resistance is common.