Certain types of flies can lay eggs on human skin, a condition known as myiasis. While unsettling, this parasitic infestation is treatable and preventable. The presence of fly larvae, or maggots, in living tissue can cause discomfort, but understanding infestation mechanisms and available interventions helps manage concerns.
The Phenomenon of Myiasis
Myiasis is the parasitic infestation of a living animal, including humans, by fly larvae. These larvae feed on the host’s dead or living tissue, liquid body substances, or ingested food. Myiasis can manifest in various forms depending on the affected body part, such as cutaneous (skin), furuncular (boil-like lesions), wound, ocular (eye), or nasal myiasis. This parasitic infection is more common in tropical and subtropical regions, but cases can occur elsewhere, particularly in travelers returning from endemic areas.
Common Flies and Infestation Pathways
Several fly species cause myiasis in humans, each employing distinct infestation methods. The human botfly (Dermatobia hominis), prevalent in Central and South America, lays its eggs on other blood-feeding insects like mosquitoes or ticks. When the carrier insect bites a human, the warmth from the host’s skin causes the eggs to hatch, and the larvae then burrow into the skin. Tumbu flies (Cordylobia anthropophaga), found in tropical Africa, often lay their eggs on soil contaminated with urine or feces, or on damp clothing left to dry outdoors. The larvae hatch within days and can then penetrate unbroken skin upon contact.
Other opportunistic flies, such as blowflies and flesh flies, are attracted to open wounds or sores. These flies deposit their eggs directly onto compromised tissue, where the larvae hatch and feed on necrotic or living tissue. This form, known as wound myiasis, can lead to significant tissue damage if left unaddressed. Some flies can also deposit eggs on mucous membranes, such as those around the eyes, nose, or mouth.
Recognizing Signs and Symptoms
The signs and symptoms of myiasis vary depending on the type of infestation and fly species. In furuncular myiasis, a painful, itchy, red bump may develop, often resembling a boil. A small central pore is visible within the lesion, which the larva uses for breathing. Individuals may report a sensation of movement under the skin.
Discharge of fluid may also be observed from the central opening. A portion of the larva’s body might be visible through this pore. Diagnosis is often made through visual inspection, and can sometimes be aided by imaging techniques.
Medical Treatment Options
Medical intervention is important for treating myiasis to ensure complete removal of the larvae and prevent complications. Surgical extraction is a common method for furuncular myiasis, where the lesion is locally anesthetized and the larva is carefully removed. The entire larva must be removed to avoid foreign-body reactions or secondary infections. Occlusion, another approach, involves covering the central breathing pore with a substance like petroleum jelly. This deprives the larva of oxygen, encouraging it to emerge from the skin for easier extraction.
For some types of myiasis or when surgical removal is challenging, medications like ivermectin may be used. This antiparasitic drug can be administered orally or topically to kill the larvae, facilitating their removal. After the larva is removed, proper wound care, including cleansing and dressing, is necessary to promote healing and prevent secondary bacterial infections.
Preventing Infestation
Preventing myiasis involves practical measures, particularly when in areas where these flies are prevalent. Wearing protective clothing, such as long-sleeved shirts and pants, can minimize exposed skin and reduce the risk of fly contact. Using insect repellents containing active ingredients like DEET or picaridin on exposed skin and clothing provides a layer of protection. Avoiding drying laundry outdoors in endemic regions is recommended, as flies like the tumbu fly can lay eggs on damp fabrics.
Maintaining good hygiene and properly caring for any wounds are important preventative steps. Wounds should be kept clean and covered to avoid attracting flies that might lay eggs in open tissue. Environmental controls, such as screening windows and doors, and proper waste management, can help reduce fly populations around living spaces.