Malaria may have evolved in prehistoric insects at least 100 million years ago, and the first vertebrate hosts of the deadly disease may have included the gigantic dinosaurs, a new study suggests.
Malaria is often thought to be of more modern origin - ranging from 15,000 to 8 million years old, caused primarily by one genus of protozoa, Plasmodium, and spread by anopheline mosquitoes. However, the ancestral forms of this disease used different insect vectors and malarial strains, and may have helped shape animal survival and evolution on Earth, according to George Poinar, from Oregon State University in US.
Poinar suggested that the origins of this deadly disease, which today can infect animals ranging from humans and other mammals to birds and reptiles, may have begun in an insect such as the biting midge more than 100 million years ago.
Earlier, researchers had implicated malaria and evolution of blood-sucking insects as disease vectors that could have played a significant role in the extinction of the dinosaurs.
"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 said.
Since the sexual reproduction stage of malaria only occurs in insects, they must be considered the primary hosts of the disease, not the vertebrate animals that they infect with disease-causing protozoa, Poinar said.
The evidence points towards the Gregarinida as a protozoan parasite group that could have been the progenitors of malaria, since they readily infect the insects that vector malaria today, he said.
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.
The study was published in the journal American Entomologist.
