Dirofilariasis in humans is caused by Dirofilaria roundworms. The main natural hosts for the three Dirofilaria species that most frequently cause disease in humans are dogs, wild canids (such as wolves and foxes) and raccoons. Humans are infected with Dirofilaria larvae through mosquito bites. Infection can result in nodules under the skin or conjunctiva. They may also present as lung granulomas (small nodules formed by an inflammatory reaction), which may appear as small nodules on chest radiographs, leading to further diagnostic procedures to exclude more serious diseases.