Malaria Is an Ancient Parasite.

From genetic data, researchers at the National Institutes of Health (NIH, 9000 Rockville Pike, Bethesda, MD 20892; Tel: 301/496-4000; Website: www.nih.gov) have concluded that the parasite is genetically more diverse and much older-at least 100,000 yr old-than previously thought.

In a second paper, the NIH-led group also found that parasites resistant to chloroquine, once the major anti-malaria drug, arose in several geographic locations and rapidly spread across continents. This finding upends the notion that chloroquine resistance developed independently in only two areas in the mid- 20th century and slowly spread to other countries from those sites.

The NIH malaria reports appear in back-to-back papers published in the July 18 issue of Nature. Taken together, the data suggest that creating vaccines or new drugs to control malaria will be quite difficult.

Plasmodium falciparum, the parasite responsible for most deadly cases of malaria, thrives in the tropics and infects approx. 300 million people annually. One to two million people, mostly children, die of the disease each year. Because of the development of drug resistance, malaria cases have been on the increase.

In the late 1990s, a group of evolutionary biologists first proposed a "Malaria Eve" hypothesis to explain the origin of the parasite. By examining 10 genes of the malaria parasite, these scientists proposed that the bug is relatively young-3,000 to 5,000 yr old-and genetically similar from place to place, and as such, should not be too difficult to control.

To explore the question in more detail, Xin-zhuan Su and Jianbing Mu, of the National Institute of Allergy and Infectious Diseases (NIAID); Wen-Hsiung Li and Kateryna Makova, of the University of Chicago; and their colleagues at the NIH National Center for Biotechnology Information (NCBI) looked for genetic differences among geographically distinct parasites. The five P. falciparum isolates they chose each hailed from a different geographical region: Southeast Asia, Africa, South America, Central America, and Papua New Guinea. The researchers compared the same 204 genes in chromosome 3 of each of these parasites to see if they could detect any nucleotide differences. This process revealed great diversity in the five genomes. Based on these differences, the scientists estimate the earliest common ...