Blowflies are common insects often seen around decaying organic matter. Recognized by their metallic blue, green, or bronze bodies, these flies are larger than typical houseflies and are attracted to decomposition odors. While usually associated with carrion, certain blowfly species can infest living human tissues, a condition known as myiasis.
How Blowflies Infest Humans
Blowflies infest humans through myiasis, a parasitic condition where fly larvae, or maggots, invade living tissue. While many fly species lay eggs on decaying matter, some are attracted to open wounds or soiled areas on living hosts. Adult female flies deposit eggs directly onto or near a wound, or sometimes on unbroken skin.
Eggs hatch into larvae within hours to a few days, depending on environmental conditions. These larvae then feed on the host’s tissue. Myiasis can manifest as cutaneous myiasis, infesting the skin, or cavitary myiasis, involving organs like the nose, sinuses, or eyes.
Species such as Cochliomyia hominivorax (New World screwworm) and Chrysomya bezziana (Old World screwworm) are notable because their larvae are obligate parasites, requiring living tissue for development and causing extensive damage. These larvae burrow head-downwards into wounds, feeding on skin and underlying tissues. Other blowfly species, like those from the Lucilia and Phormia genera, cause facultative myiasis, laying eggs in existing wounds but not invading healthy tissue. The entire life cycle, from egg to adult, can complete in less than three weeks in warm, humid conditions.
Identifying a Blowfly Infestation
Recognizing a blowfly infestation, or myiasis, involves observing specific signs and symptoms. A primary indicator is the presence of visible larvae, or maggots, on or within a wound or lesion. These larvae are pale yellow to white, worm-like, and range from 3/8 to 7/8 inches long. They have a tapered head with hook-like mouthparts and a larger, rounder rear end.
Infested individuals may experience itching, pain, or a sensation of movement beneath the skin. The infested area might develop a red bump or boil-like lesion, often with a central opening that may exude a serous or bloody discharge. In some cases, a small portion of the larva’s posterior end might be visible through this opening, allowing it to breathe.
While infestations can occur on various body parts, they are often found in areas with open wounds or poor hygiene. For instance, Cochliomyia hominivorax larvae are found in wounds or superficial body cavities like the nose. In severe instances, especially with aggressive species, the larvae can cause tissue destruction, and secondary bacterial infections are a common complication.
Preventing and Treating Infestations
Preventing blowfly infestations in humans focuses on maintaining good hygiene and proper wound care. Prompt and thorough cleaning of any cuts, scrapes, or existing wounds, followed by covering them with appropriate dressings, reduces attraction for flies seeking sites to lay eggs.
Environmental control measures also play a role. Proper waste management, such as using tightly sealed garbage cans and regularly clearing decaying organic matter, can reduce blowfly populations around living spaces. Keeping windows and doors screened also prevents adult flies from entering homes and accessing potential breeding sites.
If a blowfly infestation is suspected, seeking professional medical attention is advised. Self-treatment can be ineffective or harmful, potentially pushing larvae deeper into tissues or leading to complications. Medical professionals approach treatment by physically removing the larvae.
This removal may involve surgical extraction, especially for deeply embedded larvae, or techniques like occlusion, where the opening is covered to encourage larvae to emerge due to lack of oxygen. After larvae removal, the wound is thoroughly cleaned, and antibiotics may be prescribed to address or prevent secondary bacterial infections. Early diagnosis and treatment prevent tissue damage and other health complications.