The evolutionary origin of the malaria parasite may be older than anyone thought. A new analysis of a 100-million-year-old insect preserved in amber shows evidence for the oldest ancestral strain of malaria, meaning it likely infected not just the ancestors of mammals, but dinosaurs too.
The research is based on a biting midge from the mid-Cretaceous that contains the remains of an extinct malarial parasite (Paleohaemoproteus burmacis) that bears many similarities to the Plasmodium species that causes malaria.
“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,” said George Poinar Jr., who authored the research published in the journal American Entomologist, in a statement. Poinar also suspects that he is able to answer a long-standing question of whether or not vertebrates are the primary hosts of the parasite. He says that as malaria reproduces in insects, they instead are the primary hosts.
This ancient origin of malaria’s ancestors also informs one of Poinar’s more controversial theories. Rather than an asteroid impact – or perhaps in conjunction with one – he suggests that the parasitic infection might have contributed to the decline and eventual extinction of the dinosaurs. He claims that the evolution of the disease had the potential to have a huge impact on the evolution of animals.
“There were catastrophic events known to have happened around that time, such as asteroid impacts and lava flows,” said Poinar. “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.”
While there are many different types of malaria infecting lots of different groups of organisms, few become deadly enough to kill. For example, despite there being at least six different species of Plasmodium infecting humans, chimpanzees, and gorillas, only the human variety is deadly.
It was previously discovered that this species is derived from a type of malaria that infects gorillas, and a more recent study comparing the genetics of human malaria with two others that infect apes found something else surprising: The deadly species that infects humans and causes so much devastation isn’t actually that old – the genetics seems to imply it only originated around 10,000 years ago.
Image in text: A 100-million-year-old midge preserved in amber containing oocytes of Paleohaemoproteus burmacis, an extinct parasite similar to malaria. Poinar 2016