General and biological characteristics of blood-sucking flies (house flies)

Flies that do not suck blood play an important role in the mechanical transmission of bacterial, viral, protozoal, and helminthic diseases. A good example of such organisms is the Family Muscidae, which includes three medically important flies (Musca, stomoxys, and Glossina).

Musca domestica

The common fly is a medium-sized fly, measuring between 6 and 10 mm in length; the female is generally slightly larger than the male. The adult fly has a gray color. Its body is divided into head, thorax and abdomen. The eggs are deposited in masses of decomposing organic substances, garbage, waste or manure. The larvae hatch in 6-24 hours and feed on organic matter. They molt 2 times giving 3 larval stages. The third larva pupates within the skin of the larva. The adult emerges after a few days through a circular cut of the puparium. The complete cycle lasts about a week.

Medical significance

Indirect mechanical transmission of microorganisms (such as typhoid, polio, and bacillary dysentery), helminth eggs, and protozoan cyst. Accidental myasis. It is controlled by the sanitary disposal of waste, garbage and manure (breeding substrate) by dumping, burning or applying insecticides. Also through the control of adult flies by screening or space spraying or insecticides. Myiasis is the invasion of animal or human tissues by dipteran fly larvae.

Classification of myiasis

1. According to the habits of the flies:

. specific myiasis – in this case, flies are obligatory tissue parasites; larvae develop only in living tissues (obligatory sarcobiotics). The place of oviposition of flies is in or near living tissues. Examples, 1.) Members of the Oestridae family: Oestrus, Hypoderma, Dermatobia. 2.) Gasterophitus 3.) Cordilobia (they lay eggs on the ground or on clothing, the larvae do not penetrate intact skin, only wounded or diseased tissues).

. Semi-specific myiasis. In this case the flies are mandatory necrobiots; They lay eggs or larvae in decomposing matter but can attack tissues (optional sarcobiots) attracted by the odor emanating from diseased or injured tissue discharges, eg members of the Calliphoridea family.

. Accidental myiasis (larvae can accidentally enter tissues, eg Musca, stomoxis and Fannia).

2. According to habitat (type of tissue invaded):

. intestinal, for example, Musca, Calliphora, Lucilia and Sarcophaga.

. p. ex. gastric Eristalis

. For example, urogenital. Fannia (lays eggs in the urethral opening)

. cutaneous: traumatic (wound) myiasis invades wounds or ulcers, eg, members of the family Calliphoridae; Progressive rash, eg hypoderma and nodular, eg dermatobia

. Ocular, eg, estrus, wohlfahrtia, and sarcophaga

. aural, e.g. Wohlfahrtia and Sarcophaga

. nasopharyngeal, eg Wohlfahrtia and Sarcophaga.

The diagnosis is based on the finding of larvae in the lesion. The larvae are identified by the characteristic posterior sporacos. Live larvae can be reared to adulthood for identification.

Treatment consists of removing larvae.

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