MYIASIS (MAGGOT INFESTATION)

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MYIASIS 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, and screwfly) can create an infestation even on unbroken skin and have even been known to use moist soil and non-myiatic flies (such as the common housefly) as vector agents for their parasitic larvae.

Myiasis varies widely in the forms it takes and its effects on the victims. 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.

VECTORS IN HUMANS

• Calliphoridae (blowflies)
• Oestridae (botflies)
• Sarcophagidae (flesh-flies)

CLINICAL PRESENTATION IN HUMAN

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:

Cutaneous Myiasis: Painful, slow-developing ulcers or furuncle- (boil-) like sores that can last for a prolonged period.

Nasal Myiasis: Obstruction of nasal passages and severe irritation. In some cases facial edema and fever can develop. Death is not uncommon.

Aural Myiasis: Crawling sensations and buzzing noises. Smelly discharge is sometimes present. If located in the middle ear, larvae may get to the brain.

Ophthalmomyiasis: Fairly common, this causes severe irritation, edema, and pain.

Nosocomial Myiasis refers to myiasis in a hospital setting. It is quite frequent, as patients with open wounds or sores can be infested if flies are present. To prevent nosocomial myiasis, hospital rooms must be kept free of flies.

WOUND MYIASIS

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, mental retardation, psychiatric illness, alcoholism, diabetes, and vascular occlusive disease.

DIAGNOSIS

Intestinal myiasis and urinary myiasis are especially difficult to diagnose.

Clues that myiasis may be present include recent travel to an endemic area, one or more non-healing lesions on the skin, itchiness, movement under the skin or pain, discharge from a central punctum (tiny hole), or a small, white structure protruding from the lesion. Serologic testing has also been used to diagnose the presence of botfly larvae in human ophthalmomyiasis.

PREVENTION

To prevent myiasis in humans, there is a need for general improvement of sanitation, personal hygiene, and extermination of the flies by insecticides. Clothes should be washed thoroughly, preferably in hot water, dried away from flies, and ironed thoroughly. The heat of the iron kills the eggs of myiasis-causing flies.

TREATMENT

 First the larva must be eliminated through pressure around the lesion and the use of forceps. Secondly the wound must be cleaned and disinfected. Further control is necessary to avoid further reinfestation.

Source: wikipedia