Were dinosaurs the original hosts of malaria? A recent analysis of an ancient biting midge preserved in amber revealed that malaria evolved at least 100 million years ago, when dinosaurs could have been one of the many prehistoric reptiles to carry the disease.
Until now, malaria - a disease that is said to kill more than 400,000 people a year - was thought to be of more modern origin, specifically ranging from only 15,000 to 8 million years old. This disease can infect animals ranging from humans and other mammals to birds and reptiles.
Today, malaria is caused by a plasmodium parasite and transmitted through the bite of infected mosquitoes. However, the ancestral forms of this disease used different insect vectors - the biting midge, for example - and different malarial strains. Therefore, it is believed that malaria may have literally helped shape animal survival and evolution on Earth.
The latest study, led by George Poinar, Jr., a researcher in the College of Science at Oregon State University, showed reptiles were likely the first vertebrate hosts of malaria, which 100 million years ago would have included the dinosaurs.
"Scientists have argued and disagreed for a long time about how malaria evolved and how old it is," Poinar explained. "I think the fossil evidence shows that modern malaria vectored by mosquitoes is at least 20 million years old, and earlier forms of the disease, carried by biting midges, are at least 100 million years old and probably much older."
Ultimately, learning more about the ancient history of malaria evolution sheds light on how its modern-day life cycle works and ways in which scientists may be able to curb transmission rates.
Previously, Poinar and his wife, Roberta, demonstrated that malaria and the evolution of blood-sucking insects as disease vectors could have played a significant role in the extinction of the dinosaurs, 65 million years ago.
"There were catastrophic events known to have happened around that time, such as asteroid impacts and lava flows," Poinar added. "But it's still clear that dinosaurs declined and slowly became extinct over thousands of years, which suggests other issues must also have been at work. Insects, microbial pathogens and vertebrate diseases were just emerging around that same time, including malaria."
Currently there is no vaccine to treat malaria. In recent decades, avian malaria has been linked to the extinction of many bird species in Hawaii, especially those with no natural resistance to the disease. It follows then that different forms of malaria, with similar side effects, may have been at work millions of years ago.
Their findings were recently published in the journal American Entomologist.
