These are parasites of the lungs of mammals. Species infecting humans are found in Asia, but a species infecting mink is present in North America. They use crabs as a second intermediate host, and the cercariae use their oral stylet to penetrate the carapace. Adults are pathogenic to the definitive host because they cause an inflammation in the lungs and connective tissue proliferation. In addition, many worms migrate to sites other than the lungs and can cause serious problems there.