Myiasis is the parasitic infestation of the body of a live animal by fly larvae (maggots) which grow inside the host while feeding on its tissue. Although flies are most commonly attracted to open wounds and urine- or feces-soaked fur, some species (including the most common myiatic flies—the botfly, blowfly, and screwfly) can create an infestation even on unbroken skin and have been known to use moist soil and non-myiatic flies (such as the common housefly) as vector agents for their parasitic larvae. Because some animals (particularly non-native domestic animals) cannot react as effectively as humans to the causes and effects of myiasis, such infestations present a severe and continuing problem for livestock industries worldwide, causing severe economic losses where they are not mitigated by human action. Although typically a far greater issue for animals, myiasis is also a relatively frequent disease for humans in rural tropical regions where myiatic flies thrive, and often may require medical attention to surgically remove the parasites.Myiasis varies widely in the forms it takes and its effects on those affected. Such variations depend largely on the fly species and where the larvae are located. Some flies lay eggs in open wounds, other larvae may invade unbroken skin or enter the body through the nose or ears, and still others may be swallowed if the eggs are deposited on the lips or on food. There can also be accidental myiasis which E. tenax can cause in humans via water containing the larvae or in contaminated uncooked food.
The American Medical Association and Centers for Medicare and Medicaid Services recently clarified the reimbursement guidelines to the wound care community for medicinal maggots, and this therapy may soon be covered by insurance. The larvae of the green bottle fly (a type of blow-fly) are now used exclusively for this purpose, since they preferentially devour only necrotic tissue, leaving healthy tissue intact. This is an important distinction, as most other major varieties of myiasitic fly larvae attack both live and dead wound tissue indiscriminately, effectively negating their benefit in non-harmful wound debridement. Medicinal maggots are placed on the wound and covered with a sterile dressing of gauze and nylon mesh. However, too many larvae placed on the wound could result in healthy tissue being eaten, efficiently creating a new wound, rendering it as a type of myiasis. History
Maggot therapy has a long history and prehistory. The indigenous people of Australia used maggot therapy, and so do the Hill Peoples of Northern Burma, and possibly the Mayans of Central America. Surgeons in Napoleons armies recognized that wounded soldiers with myiasis were more likely to survive than those without the infestation. In the American Civil War, army surgeons treated wounds by allowing blowfly maggots to clean away the decayed tissue.William Baer, an orthopedic surgeon at Johns Hopkins during the late 1920s, used maggot therapy to treat a series of patients with osteomyelitis, an infection of bone or bone marrow.