Myiasis or Maggots is the parasitic infestation of the body of a live mammal by fly larvae (maggots) that 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 screw fly) can create an infestation even on unbroken skin and have even been known to use moist soil and non-myiatic flies (such as the comm on housefly) as vector agents for their parasitic larvae.
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.
Myiasis producing larvae attack three main parts of the body: cutaneous tissue (furuncular and creeping), body cavities, and body organs. Lesions with foul discharge or blood attract and stimulate the female insect to deposit eggs on them.
However, larvae may burrow into and destroy the tissue. Rapid destruction of adjacent tissues, including bone, may result in the death of the host. Tissue destruction may occur by mechanical means and by the production of collagenase. Myiasis is also frequently seen in adults, especially those who are mentally retarded.
Nasal Myiasis causes obstruction of nasal passages and severe irritation. In some cases facial edema and fever can develop. Death is not uncommon.
Aural Myiasis causes crawling sensations and buzzing noises. Smelly discharge is sometimes present. If located in the middle ear, larvae may get to the brain.Ophthalmomyiasis is fairly common, this causes severe irritation, edema, and pain.
The main symptoms of nasal myiasis are foreign body sensation and itching in throat, being followed by cough and then other various, respiratory and nasal manifestation such as nasal discharge, sneezing, laryngospasm, dyspnea and stridor.
The diagnosis of myiasis is made by seeing the larval movement. Since the nasal cavity has inaccessible areas, removal of maggots can be difficult by conventional instrument and several settings are required. To overcome this problem, a nasal endoscope can be used for a direct vision.