Millions of people in Latin America have been invade by a parasite – a trypanosome called Trypanosome cruzi. They are passed on through the bite of the blood-sucking assassin bug and they cause Chagas disease, a potentially fatal illness that affects the heart and digestive system. The infections are long-lasting; it can take decades for symptoms to show and a third of infected people eventually die from the disease. But T.cruzi does much more than invade our flesh and blood; it also infiltrates our genomes.

According to new research from Mariana Hecht and a team of Brazilian scientists, T.cruzi has the ability to inveigle its DNA rings into the genomes of those it infects. Once inside, the parasite genes