Myiasis

 

Myiasis

PKGhatak,MD.

Several species of flies seek living animals, including humans, for lying eggs, so that the newly hatched maggots will have instant source of food to feed on and grow rapidly. Maggot infestation of humans was first described by Frederick William Hope of Jamaica in 1840 when he described a man with maggots eating away his flesh.

The term Myiasis is reversed for invasion by maggots of otherwise normal individuals. Maggots deliberately applied for cleaning and debridement of chronic wounds are not included under this term.

An outline of the life of maggots: Two species of flies - Blowfly and Housefly, seek out humans to lay eggs on any exposed part of the body, from the scalp to the sole of feet. Each female fly lays about 100 to 300 eggs. Depending on the outside temperature and the type of fly, these eggs hatch in 8 to 12 hours and immediately borrow under the skin and begin feeding and growing. In about 50 to 60 hours they are fully grown and all the maggots are similar in size and maturity, They stop feeding and fall off the body and pupate. They later emerge as adult flies.

These three species of fly are responsible for most Myiasis – Botfly, Tumbufly and Screwworm fly.

Myiasis is described under several categories based on the location of the maggots and the symptoms they produce. These categories are Cutaneous, Creeping, Wound, Body cavities, and Accidental Myiasis.

Types of Myiasis.

Cutaneous Myiasis: The back of the head and skin of the back are the favorite place of this fly to lay eggs. Growing maggots produce bumps on the skin. These lesions are painful and itchy. On close examination, a hole is visible on the top of a bump, through which the maggot gets its air to breathe. These wholes are used to pull maggots out with a pair of forceps.

Creeping Myiasis: Humans are an accidental host for this parasitic maggot. Maggots can not develop in humans, so the maggots move around underneath the skin and give the victims a creepy sensation. Surgical removal of maggots is necessary.

Body cavity Myiasis: The fly deliberately targets ear canals, nose, mouth and eyes. Growing maggots produce secondary infection and usually lead to serious respiratory, gastrointestinal and neurological complications. From the roof of the nose or eye sockets the maggots penetrate the base of the brain. Meningitis, encephalitis and brain abscesses are usual complications. Surgical removal of maggots is often required.

Wound Myiasis: Open wounds are within easy reach of flies. Maggots eat away dead and dying tissue and, in general, do not invade normal living tissues.

Accidental Myiasis: Farmers in Africa and South American countries, at times have to drink water from the nearby streams, which are usually contaminated with fly eggs. These eggs hatch in the stomach of the victims. Growing maggots produce nausea, vomiting and diarrhea. Maggots die due to low oxygen in the G-I tract or are removed by administration of medication and purgation.

In the USA Myiasis is not seen in the local population.

South American countries and tropical Africa are endemic to Myiasis.

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