Malaria started out as a parasite in birds, then evolved to colonise bats, and from there spread to other mammals, says a new study on the evolution of the parasite found.
Malaria affects around 500 million people every year, but humans are not the only ones - different species of malaria parasite can infect birds, bats, and other mammals too, researchers said.
“We cannot begin to understand how malaria spread to humans until we understand its evolutionary history. In learning about its past, we may be better able to understand the effects it has on us,” said Holly Lutz from Cornell University in the US.
Malaria is a parasitic single-celled organism that reproduces in the bloodstream of its host and is transferred between hosts by insects like mosquitoes. Different species of malaria live in different species of host animals.
Blood samples to identify mutations
Researchers took blood samples from hundreds of East African birds, bats, and other mammals and screened the blood for the parasites. When they found malaria, they took samples of the parasites’ DNA and sequenced it to identify mutations in the genetic code.
From there, they were able to perform what is called “phylogenetic analysis” to determine how different malaria species are related.
In analysing the genetic codes of the malaria parasites, researchers were able to find places where the DNA differed from one species to the next.
Then, they used powerful computing software to determine how the different species evolved and how they are related to each other.
This phylogenetic analysis relied on large sample sizes and DNA from many different host species of bats and birds, because otherwise, the picture would be incomplete, researchers said.
“Trying to determine the evolutionary history of malaria from just a few specimens would be like trying to reconstruct the bird family tree when you only know about eagles and canaries,” said Lutz.
“There is still more to discover, but this is the most complete analysis of its kind for malaria to date,” she said.
The analysis showed that malaria has its roots in bird hosts, from which it spread to bats, and then on to other mammals.
“It is not that bats are spreading malaria - we get different species of malaria than they do, and we cannot get it from them. Instead, by looking at patterns of mutations in the DNA of the different malaria species, we are able to see when it branched off from one host group into another,” said Lutz.
“It started out as a parasite in birds, and then it evolved to colonise bats, and from there, it is evolved to affect other mammals,” she said.
The findings were published in the journal Molecular Phylogenetics and Evolution.
