Malaria -- often thought to be of more modern origin -- may have killed dinosaurs and the origin of this deadly disease may have begun in an insect such as the biting midge more than 100 million years ago, researchers reveal.
A new analysis of the prehistoric origin of malaria suggests that it evolved in insects at least 100 million years ago, and the first vertebrate hosts of this disease were probably reptiles, which at that time would have included the dinosaurs.
Malaria, that still kills more than 400,000 people a year, is often thought to have been originatd 15,000-eight million years old - caused primarily by one genus of protozoa, Plasmodium, and spread by anopheline mosquitoes.
"But the ancestral forms of this disease used different insect vectors and different malarial strains, and may literally have helped shape animal survival and evolution on Earth," said George Poinar, Jr, researcher at Oregon State University.
Scientists have argued and disagreed for a long time about how malaria evolved and how old it is.
"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," Poinar suggested in a paper appeared in the journal American Entomologist.
In previous work, Poinar and his wife Roberta, implicated malaria and the evolution of blood-sucking insects as disease vectors that could have played a significant role in the extinction of the dinosaurs.
Understanding the ancient history of malaria evolution, Poinar said, might offer clues to how its modern-day life cycle works, how it evolved, and what might make possible targets to interrupt its transmission through its most common vector - the Anopheles mosquito.
Understanding the evolution of malaria also takes one on a worldwide journey, according to evidence found in insects preserved in amber.
Poinar was the first to discover a type of malaria in a 15-20 million-year-old fossil from the New World, in what is now the Dominican Republic.
It was the first fossil record of Plasmodium malaria, one type of which is now the strain that infects and kills humans.
The team argues that insects carried diseases that contributed to the widespread extinction of the dinosaurs around the "K-T boundary" about 65 million years ago.
There were catastrophic events known to have happened around that time, such as asteroid impacts and lava flows.
"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.," the authors noted.
Avian malaria has been implicated in the extinction of many bird species in Hawaii just in recent decades, especially in species with no natural resistance to the disease.
"Different forms of malaria, which is now known to be an ancient disease, may have been at work many millions of years ago and probably had other implications affecting the outcome of vertebrate survival," Poinar noted.
The first human recording of malaria was in China in 2,700 B.C., and some researchers say it may have helped lead to the fall of the Roman Empire.
