DNA Fossils Found of Dreadful Human Diseases Originating in Birds

A team of researchers from 11 institutions in five countries recently discovered a DNA fossil of a human-infecting parasite. However, that they were found in certain species of tropical birds suggests that these parasitic worms transferred from birds to humans several million years ago.

According to the study published in the journal Nature Communications, DNA parasites could leave evidence of parasitic interaction when jumping to its host's genome. This evidence, a DNA fossil of some sort, can be found millions of years later. The small stretches of DNA that have the ability to relocate from one place to another are called transposable elements.

A new transposable element was discovered by the researchers. It tends to occur in some bird genomes but not others. Upon searching DNA databases of other animals, the researchers discovered that this transposable element discovered in tropical birds can only be found in nematode worms, which are parasites that infect humans and other animals. Nematode worms are known to cause serious human tropical disease such as lymphatic filariasis and loiasis.

The researchers then compared the DNA sequence of the transposable element in each instance and discovered that the DNA transfer between the birds and the nematodes occurred in two waves across entire tropics, including Madagascar. The birds involved in the transfer belong to the charismatic group which includes parrots, hummingbirds and manakins.

According to the press release of Uppsala University, the study suggests that these human parasites infect only birds from at least 25 to 17 million years ago. There is now evidence found of these parasites in the genomes of mammals during that time. The study also shows that the bird parasite were widespread during that time due to cross-infection between different bird groups that occurred in the world's major tropical regions.

These findings are significant in understanding the relatedness and interactions between specific host and parasite species.