CORVALLIS, Ore. One of the most comprehensive analyses yet done of the ancient history of insect-borne disease concludes for the first time that malaria is not only native to the New World, but it has been present long before humans existed and has evolved through birds and monkeys.
The findings, presented in a recent issue of American Entomologist by researchers from Oregon State University, are based on the study of insect specimens preserved in amber.
The study outlines the evolution of several human diseases, including malaria, leishmaniasis and trypanosomiasis. It makes clear that these pathogens have existed for at least 100 million years, and suggests that efforts to conquer them will be an uphill battle against such formidable and adaptive foes.
"Amber tells us that these diseases have been here for many millions of years, have co-evolved with their hosts and move readily from one species to another," said George Poinar, Jr., a professor of zoology at OSU and one of the world's leading experts on the study of fossils in this semi-precious stone.
"Malaria is one of the greatest insect-borne killers in human history, and more than one million people a year are still dying from it," Poinar said. "But the evolutionary record suggests it can easily change its protein coat in response to vertebrate immune reactions. That's why it's always becoming resistant to drugs, and efforts to create vaccines will be very difficult."
Insects preserved for tens of millions of years are offering new clues to the ancient history of these diseases. Blood-feeding vectors trapped eons ago in oozing tree sap reveal in near-perfect detail stages of vertebrate pathogens they were carrying when they became entombed.
"Most people think of malaria as a tropical disease, which today it primarily is," Poinar said. "But historically it occurred in many parts of the world, including temperate zones."
|Contact: George Poinar, Jr. |
Oregon State University