Using ancient DNA extracted from human skeletons, an international team of researchers representing 80 institutions and 21 countries has been able to uncover how and when malaria spread around the world, including how the disease first arrived in the Americas.
In the study, published June 12 in the scientific journal Nature, the team identified the first known case of P. falciparum malaria at the high Himalayan site of Chokopani (about 800 BC) in Nepal, at an altitude of 2,800 meters above sea level. .
Mysterious fascism
Malaria is one of the most deadly infectious diseases in the world, and is caused by several species of single-celled parasites that are transmitted through the bite of an infected Anopheles mosquito. Malaria is particularly mysterious because the parasitic infection causes common symptoms of a wide range of diseases, and when it kills it leaves no physical marks on human bones for archaeologists to find.
But advances in ancient DNA sampling over the past decade have enabled scientists to recover disease-causing DNA from human skeletons thousands of years old. Traces of pathogens that have invaded a person’s blood – including the parasites that cause malaria – remain embedded in their bones and teeth after death.
In the new study, researchers were able to study two parasites that cause malaria: Plasmodium falciparum and Plasmodium vivax.
“From an evolutionary biology perspective, malaria is one of the most interesting pathogens to look at because of its profound impact on the human genome,” said study lead author Megan Michel, a doctoral researcher at Harvard University and the Max Planck Institute for Human Evolution in Germany.
The researcher added in an interview with Al Jazeera Net that there are several copies or variants of genes involved in the formation of red blood cells – where malaria parasites reproduce – which can provide resistance to the disease. These variants are more common among people whose ancestors lived in areas with high rates of malaria. “Using ancient DNA allows us to go back in time and glimpse what the genomes of these pathogens looked like in the past and how they evolved alongside their human hosts,” she says.
DNA testing
To find out how these parasites spread around the world, researchers examined DNA from the remains of 36 individuals whose ages span 5,500 years and hail from five continents. By comparing the genomes of the Plasmodium parasites that infected these individuals, the researchers traced when and how malaria moved from one region to another.
The researchers believe that this data can help scientists; Not only in unraveling the history of malaria, but also in better dealing with the disease today. “We can use this data to understand not only the pathology, but also the evolutionary path of malaria, and perhaps even new ways to overcome it,” said the study’s lead researcher. “After all, it is one of the greatest killers of our time, as malaria kills more than 600,000 people per year.” All over the world every year.
The research also resulted in determining how malaria arrived in the Americas through analyzing the DNA of an individual who lived high in the Andes in Peru at a site called Laguna de los Condors about 500 years ago. The similarities between the P. vivax strain that infected this individual and other strains prevalent in Europe at the time suggest that European colonists brought malaria to the New World, according to the press release published on the Eurik Alert website.
“This is exciting because it tells us how pathogens arrived in the Americas,” Michelle said. “Those strains that were transmitted early in the colonization process survived, and we found genomic evidence linking them to the parasites that spread in the region today.”
Unexpectedly, the team also found evidence of malaria in cold climates. A 2,800-year-old skeleton from Chokhubani, a site high in the Himalayas, showed signs of Plasmodium falciparum infection – an important discovery because Chokhubani is so high, cold, and dry that mosquitoes that It carries malaria to survive in it.
The researchers concluded that this person may have contracted the disease in a lowland area in the same way that modern travelers transport pathogens around the world.