Under a microscope, the researchers saw that the samples contained the eggs of two of the world’s most common and widespread intestinal parasites: whipworms (Trichuris trichiura), which cause the infection known as trichocephalus, and giant roundworms (Ascaris lumbricoides), the largest of the nematodes found in human intestines, with adults that can grow to more than 1 foot (30 centimeters) long.
People with a light load of these worms may experience no symptoms. But when whipworms and giant roundworms heavily colonize the digestive tract, they compete with their hosts for food, siphoning off the nutrients that would normally be absorbed in the intestines. Eggs of the parasites pass through the feces and spread to other hosts by ingestion (say, when a human doesn’t wash their hands and spreads the parasite to food or other objects that get consumed). That means infections are most common in places with poor hygiene and sanitation as well as areas where human waste is used as fertilizer or where people defecate in the soil.
Story: Megan Gannon, LiveScience | Photo: Anastasiou and Mitchell, International Journal of Paleopathology