Researchers Develop Genetic Barcode to Identify Geographical Origin of Malaria Parasites
New Tool May Improve Disease Surveillance
Researchers have developed a genetic barcode that accurately identifies the geographical origin of malaria-causing parasites. The barcode could eventually be used to identify the source of malaria outbreaks and to track the spread of the disease. The study, which highlights the importance of conducting field studies in malaria-endemic areas, appears in the June 13, 2014, online issue ofNature Communications.
Dr. Fairhurst’s Cambodian colleague approaches a villager’s home to assess a patient with malaria. Credit: NIAID
Malaria is caused by Plasmodium parasites, and P. falciparum is the deadliest. According to the latest estimates from the World Health Organization, there were over 200 million cases of malaria in 2012. While malaria death rates have fallen over 40 percent since 2000, resistance to artemisinin-based antimalarial drugs, the standard treatment for the disease, has emerged in five countries—Cambodia, Laos, Myanmar, Thailand, and Vietnam—with no alternative antimalarial drugs available.
NIAID supports research in more than 100 countries. Rick Fairhurst, M.D., Ph.D., along with his team from NIAID’s Laboratory of Malaria and Vector Research, has conducted field studies in Mali and Cambodia for several years, providing treatment for malaria patients and obtaining samples from malaria-endemic regions. Such studies are essential for public health monitoring, such as tracking drug resistance, and for providing valuable field samples and clinical data to the research community.
Results of Study
An international team of researchers led by the London School of Hygiene and Tropical Medicine has developed a method for identifying the geographical origins of P. falciparum parasites by using genetic information as a “barcode.” The researchers obtained genetic data from parasites isolated from 14 countries in 5 global regions—West Africa, East Africa, Southeast Asia, Oceania (Pacific islands near Australia), and South America—including data supplied by Dr. Fairhurst’s field studies.
Previously, researchers tried identifying a malaria barcode using genes found in the nucleus of parasite cells but were less successful. In this study, the researchers focused on genes that are found outside the nucleus, in two cellular structures called the mitochondrion and apicoplast. By analyzing these genes, the researchers found 23 key regions that could reliably predict the geographical origin of a parasite.
The study is the first to identify an accurate barcode for determining the geographical origin of P. falciparum parasites. This surveillance tool may be used to combat outbreaks and track the spread of parasites, including those resistant to drugs.
Furthermore, this study is the first to comprehensively analyze genetic data from the mitochondria and apicoplasts of malaria parasites. These structures are attractive to researchers because they are necessary for the survival of malaria parasites but are not found in human cells, providing a parasite-specific drug target.
The researchers are applying similar techniques to identify a barcode for other malaria parasites, such as P. vivax and P. knowlesi. For example, P. vivax is a major concern in Cambodia, where multidrug-resistant malaria has emerged. Continuous field studies are necessary to provide real-time samples as parasites change.
The researchers also are interested in examining parasite data obtained from malaria-endemic regions not assessed in this study, such as India, the Caribbean, and Central America. However, adequate samples from these regions are not yet available.
Preston MD, Campino S, Assefa SA, Echeverry DF, Ocholla H, Amambua-Ngwa A, Stewart LB, Conway DJ, Borrmann S, Michon P, Zongo I, Oue´draogo J, Djimde AA, Doumbo OK, Nosten F, Pain A, Bousema T, Drakeley CJ, Fairhurst RM, Sutherland CJ, Roper C, and Clark TG. A barcode of organellar genome polymorphisms identifies the geographic origin of Plasmodium falciparum strains. Nature Communications (2014)