Parasitic giant roundworms (Ascaris lumbricoides) extracted from an infected Kenyan child. Photo courtesy of J. Gathany.
Being infected by parasitic helminths or worms isn’t just a Third World problem. It’s a global phenomenon. Example: The Centers for Disease Control and Prevention says an estimated 576 to 740 million people around the world are infected by hookworms alone. In the United States, the most common worm parasite is Enterobius vermicularis or the pinworm.
A new study in the UK, however, offers this upside to being infected: If you’re carrying one type of parasite, your risk of catching a second infection may be less.
Cardiff researchers analyzed data from school-age children in Tanzania infected with the most common forms of parasitic worms: giant roundworm (Ascaris lumbricoides), roundworm (Trichuris trichiura) and the aforementioned hookworm, of which there are two species that commonly infect humans.
They found that co-infection is a very important risk factor, sometimes more important than any other factor, such as a child’s living conditions, behavior and gender. Sometimes the risk of a second infection increases with the first, but not always.
The discovery has practical import. It more fully explains the relative risks of co-infection – when a person carries more than one parasite species – and suggests that efforts to control infections may need to be fine-tuned so that resources are not wasted targeting the wrong things.