Nodule worms infect the gastrointestinal tracts of a number of mammalian species, including humans and other primates. This study sought to identify the species of nodule worms causing infections within and around an East African national park in Uganda where monkeys and apes co-occur and overlap with people. Some primates, particularly those traversing large distances in small groups, were most susceptible to nodule worm infection. Additionally, molecular analyses identified three separate groups of nodule worm that could not be distinguished based on microscopic examination of their eggs. One of these groups was found in humans as well as other primates and had not previously been genetically characterized. These results suggest that certain types of nodule worm may be restricted to particular hosts, while others may be transmitted among primates, including humans. Nodule worms are currently thought to be a human health concern only in some West African countries. This research suggests that nodule worms have a broader geographic impact in humans than previously appreciated.