A secret war between cane toads and parasitic lungworms is raging across Australia

When the first cane toads were brought from South America to Queensland in 1935, many of the parasites that troubled them were left behind. But deep inside the lungs of at least one of those pioneer toads lurked small nematode lungworms.

Almost a century later, the toads are evolving and spreading across the Australian continent. In new research published in Proceedings of the Royal Society B, we show that the lungworms too are evolving: for reasons we do not yet understand, worms taken from the toad invasion front in Western Australia are better at infecting toads than their Queensland cousins.

An eternal arms race

Nematode lungworms are tiny threadlike creatures that live in the lining of a toad’s lung, suck its blood, and release their eggs through the host’s digestive tract. The larva that hatch in the toad’s droppings lie in wait for a new host to pass by, then penetrate through its skin and migrate through the amphibian’s body to find the lungs and settle into a comfortable life, and begin the cycle anew.