The name of the condition derives from ancient Greek μυῖα (myia), meaning "fly". Signs and symptoms
How myiasis affects the human body depends on where the larvae are located. Larvae may infect dead, necrotic (prematurely dying) or living tissue in various sites: the skin, eyes, ears, stomach and intestinal tract, or in genitourinary sites. They may invade open wounds and lesions or unbroken skin. Some enter the body through the nose or ears. Larvae or eggs can reach the stomach or intestines if they are swallowed with food and cause gastric or intestinal myiasis.Several different presentations of myiasis and their symptoms:

Wound
Wound myiasis occurs when fly larvae infest open wounds. It has been a serious complication of war wounds in tropical areas, and is sometimes seen in neglected wounds in most parts of the world. Predisposing factors include poor socioeconomic conditions, extremes of age, neglect, mental disability, psychiatric illness, alcoholism, diabetes, and vascular occlusive disease. Eye
Myiasis of the human eye or ophthalmomyiasis can be caused by Hypoderma tarandi, a parasitic botfly of caribou. It is known to lead to uveitis, glaucoma, and retinal detachment. Human ophthalmomyiasis, both external and internal, has been caused by the larvae of the botfly. Cause
Life cycle
The life cycle in sheep is typical of the disease. The female flies lay their eggs on the sheep in damp, protected areas of the body that are soaked with urine and feces, mainly the sheeps breech (buttocks). It takes approximately eight hours to a day for the eggs to hatch, depending on the conditions.
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.