What is cutaneous myiasis?

Cutaneous myiasis is a skin inflammatory reaction caused by fly larvae entering the skin of the body. This disease often occurs in some pastoral areas of my country, such as Inner Mongolia, Tibet, Qinghai and other places. When people suffer from cutaneous myiasis, it will cause infection and skin damage, and often cause low fever, nausea, numbness of the limbs, pain and other symptoms.

Causes

It is mainly caused by the genus Dermoptera, including cattle Dermoptera, pattern Dermoptera and deer Dermoptera. The development process of the genus Hypoderma is divided into four stages: egg, larva, pupa and adult. Due to the different types and habits of flies, there are several ways of infection:

1. Maggots lay eggs directly on human skin, hair, or clothing. When the eggs hatch into larvae, they pass through normal skin and parasitize in the subcutaneous tissue.

2. Fly eggs are brought to the skin by certain mosquitoes when they suck human blood. After hatching, the larvae enter the skin by sucking the wound (such as human skin flies).

3. Laying eggs directly in skin wounds or skin ulcers and living in decaying tissues (such as horse flies and flesh flies) is called traumatic myiasis.

Clinical manifestations

Before the skin lesions appear, patients often feel general discomfort, such as low fever, headache, dizziness, nausea, fatigue, insomnia, numbness of the limbs, and local skin pain, which worsens at night. There are two main types of skin lesions:

1. Furunculosis type

Several months after infection, migratory wheal-like lumps of normal skin color or redness, about the size of an almond kernel, appear above the skin surface and deep under the skin. The lump gradually increases in size, the itching intensifies, and there is a sense of worms crawling. The mass is often movable. Later, the lesions increase in size and swelling intensifies, with purple-red bloody blisters appearing in the center. After rupturing, larvae (maggots) and a small amount of yellow mucus or pus are discharged. After 2 to 3 days, the inflammation gradually subsides, leaving scars after healing. It is generally more common in loose skin areas, such as the eyelids, lips, abdomen, waist, and deep forearms.

2. Creeping rash

The skin appears red and swollen in a zigzag pattern with a blister at the end. This is a sign of larval activity, with the larvae located in front of the blister.

A small number of patients may experience an urticaria-like reaction when the maggots begin to burrow into the human body. There are also reports of patients with strong systemic allergic reactions such as remittent fever, generalized lymphadenopathy, and anemia.