April 19, 2024

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Simply Consistent

General and Biological Features of the Non-Blood Sucking Flies (House Flies)

Non blood sucking flies play a great role in mechanical transmission of bacterial, viral, protozoan and helminthic diseases. A good example of such organisms is the Family Muscidae which includes three flies of medical importance (Musca, stomoxys and Glossina)

Musca domestica
Housefly is a medium-sized fly, measuring between 6 and 10mm in length; the female is generally slightly larger than the male. Adult fly has a gray color. Its body is divided into head, thorax, and abdomen. Eggs are laid into masses of decaying organic substances, garbage, refuse or manure. Larvae hatch in 6-24 hours and feed on organic matter. They molt 2 times giving 3 larval stages. The third larva pupates inside the larval skin. The adult emerges after a few days through a circular cut of the puparium. The whole cycle takes about one week.

Medical Importance
Indirect mechanical transmission of microorganisms (as typhoid, poliomyelitis and bacillary dysentery), eggs of helminthes and cyst of protozoa. Accidental myasis. It is controlled by sanitary disposal of refuses, garbage and manure (breeding media) by dumping, burning or application of insecticides. Also by control of adult flies by screening or space spraying or insecticides. Myiasis is invasion of tissues of animals or man by larvae of dipterous fly.

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 sarcobiots). The place of flies’ oviposition is located in or near living tissues. Examples, 1.) Members of family Oestridae: Oestrus, Hypoderma, Dermatobia. 2.) Gasterophitus 3.) Cordilobia (lay eggs on ground or clothing, larvae do not penetrate unbroken skin, only wounded or diseased tissues).

. Semi-specific myiasis. In this case flies are obligatory necrobiots; they lay eggs or larvae on decaying matter but may attack tissues (facultative sarcobiots) attracted by specific emanating odor from discharges of diseased tissues or wounds, e.g members of family Calliphoridea.

. Accidental myiasis (larvae may accidentally get in the tissues, e.g Musca, stomoxis and Fannia).

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

. intestinal e.g Musca, Calliphora, Lucilia and Sarcophaga.

. gastric eg. Eristalis

. Urogenital eg. Fannia (lays eggs on urethral opening)

. cutaneous: Traumatic (wound) myiasis invade wounds or ulcers eg, members of family Calliphoridae; Creeping eruption eg Hypoderma and Nodular eg Dermatobia

. Ocular eg Oestrus, Wohlfahrtia and Sarcophaga

. aural eg, Wohlfahrtia and Sarcophaga

. nasopharyngeal eg Wohlfahrtia and Sarcophaga.

Diagnosis is based on finding of larvae in the lesion. Larvae are identified by the characteristic posterior sporacles. Living larvae may be reared to adult stage for identification.

Treatment is by the removal of larvae.