This past April, Bill Gates revealed to the Internet the deadliest animal in the world. It wasn’t sharks or snakes, he points out, or even humans. In fact, it’s mosquitoes — for their overwhelming propensity to carry malaria and the parasite that causes it. Now researchers have developed a method to trace the origin of these infections via genetic “barcodes.”
A team from the London School of Hygiene & Tropical Medicine published the study, which found several short genetic sequences in the parasites’ DNA were distinct depending on which geographic regions they came from. This information — culled from over 700 P. falciparum malaria parasites from patients in 14 countries in West Africa, East Africa, South East Asia, Oceania, and South America — could hold the power to more effective malaria prevention and treatment programs.
"Being able to determine the geographic origin of malaria parasites has enormous potential in containing drug-resistance and eliminating malaria,” lead author Dr. Taane Clark, professor of Genetic Epidemiology and Statistics, said in a statement. “Our work represents a breakthrough in the genetic barcoding of P. falciparum, as it reveals very specific and accurate sequences for different geographic settings.”
To put the findings in perspective, the World Health Organization estimates that malaria caused 627,000 deaths in 2012, despite the haunting fact that the disease is both preventable and curable. Malaria most often crops up among African children; fortunately, mortality rates have fallen consistently since the year 2000, in Africa and around the world more broadly. Since the new millennium, malaria mortality rates have fallen 42 percent globally and 54 percent among African children.
The team’s new barcode produced an accuracy rate of 92 percent. It relies on specific patterns of genetic sequences found in the DNA, which lives in the mitochondria and apicoplasts of the cells. These sequences corresponded directly to the specific location where the team found the strain of P. falciparum. In field, simple finger-prick blood samples from malaria patients would allow the rapid gene sequencing to determine the parasite’s history, and help in "malaria elimination and resistance containment,” said co-author Dr. Cally Roper, senior lecturer in Malaria Genetics.
But P. falciparum isn’t the only parasite that leads to malaria. Other species, such as P. vivax, P. malariae, and P. ovale also cause the disease in humans. Researchers hope their latest success with the one strain in several locations will offer a broader application for other parasite species around different parts of the world. “We are currently extending the barcode to include other populations,” said Clark, “such as India, Central America, southern Africa and the Caribbean, and plan to include genetic markers for other types malaria, such as P. vivax."
Source: Preston M, Campino S, Assefa S, et al. A barcode of organellar genome polymorphisms identifies the geographic origin of Plasmodium falciparum strains. Nature Communications. 2014.