biopsy for a pathologic assessment. This has been shown to be the most significant medical consequence of human infection by the canine heartworm. Patients are infected with the parasite through the bite of an infected mosquito, which is the same mechanism that causes heartworm infection in dogs. D. immitis is one of many species that can cause infection in dogs and humans. It was thought to infect the human eye, with most cases reported from the southeastern United States. However, these cases are now thought to be caused by a closely related parasite of raccoons, Dirofilaria tenuis. Several hundred cases of subcutaneous infections in humans have been reported in Europe, but these are almost always caused by another closely related parasite, Dirofilaria repens, rather than the dog heartworm. There are proven D. immitis infections, but humans rarely get infected with heartworms due to the larvae never fully maturing. When the heartworm microfilariae migrate through the skin, they often die since heartworms cannot survive in a human host, even if they make it into the bloodstream. Once the heartworms die, the immune system in the human body reacts to their tissue with inflammation as it tries to destroy the heartworms. When this happens, the condition is called pulmonary dirofilariasis. Heartworms in humans is not a serious problem unless they are causing pain, discomfort, and other noticeable symptoms. References Further reading External links American Heartworm Society Founded in 1974, the American Heartworm Society is internationally recognized as the definitive authority with respect to heartworm disease in dogs and cats. Preventing Heartworm Infection in Dogs (VeterinaryPartner.com) Overview and main concepts of Dirofilaria immitis (heartworm) infection (MetaPathogen.com) Mosquito-borne Dog Heartworm Disease (University of Florida Extension Bulletin) Case Study of Canine Heartworm Disease (from the University of California, Davis) Case Study of Feline Heartworm Disease (from the University of California, Davis) Case Study of Canine Heartworm Disease (from the University of California, Davis) Spirurida Parasitic nematodes of mammals Parasites of dogs Parasites of cats Parasitic nematodes of humans Veterinary helminthology Zoonoses Nematodes described in 1856