The consumption of living tissue by fly larvae is a parasitic infestation known as myiasis. This phenomenon involves the immature stage using a live animal host for sustenance. Understanding this process requires distinguishing between flies that consume only dead matter and those that target living flesh.
Defining Flesh-Eating Flies
Flies that target a host’s tissues are distinguished by their larval feeding habits. Most flies involved belong to three primary families: Calliphoridae, Sarcophagidae, and Oestridae. The fundamental difference lies in whether they are necrophagous, feeding only on decaying organic matter, or parasitic, feeding on living tissue.
Obligate parasites, like the New World screwworm (Cochliomyia hominivorax) or all species in the Oestridae family, must develop on living tissue to complete their life cycle. Facultative parasites, such as some blowflies (Calliphoridae) and flesh flies (Sarcophagidae), typically feed on carrion but can opportunistically infest an existing wound. This distinction is important because obligate parasites actively seek out and consume healthy tissue, whereas facultative species usually target compromised or necrotic areas.
The Larval Stage and Tissue Consumption
Tissue consumption is carried out by the fly’s immature stage, the larva or maggot. Adult female flies are attracted by the odors of wounds, bodily excretions, or moist skin, where they deposit eggs or, in some species, live larvae. The New World screwworm, for instance, lays 200 to 300 eggs near a wound, which hatch quickly, often within a day.
Upon hatching, the larvae immediately begin to burrow into the host’s flesh. They are physically adapted for this, possessing rings of backward-facing spines that allow them to tunnel deeper into the tissue. The larvae chemically break down the host’s protein structures using powerful excretions and secretions. These releases contain proteolytic enzymes, such as proteases, which liquify the surrounding tissue. The maggot then ingests this liquefied material, consuming the host’s living flesh from the inside out.
Manifestations of Myiasis in Hosts
The infestation of a live vertebrate animal by fly larvae is scientifically known as myiasis. It presents in various forms depending on the fly species and the location of the infestation. Cutaneous myiasis is a common form, manifesting as lesions on the skin.
Furuncular myiasis, caused by species like the human botfly (Dermatobia hominis), involves a single larva burrowing under the skin to create a painful, boil-like nodule with a central breathing pore. Wound myiasis occurs when larvae infest open injuries, leading to massive tissue destruction, foul-smelling discharge, and a failure of the wound to heal. More serious forms include cavitary myiasis, which affects orifices like the nose, ears, or eyes. The feeding activity can erode bone and soft tissue, potentially leading to severe secondary infections, loss of function, or even death if left untreated.
Prevention and Management
Preventing myiasis centers on minimizing the factors that attract adult flies and protecting potential entry points on the host. Maintaining strict cleanliness and proper hygiene is necessary in all areas where parasitic flies are present. This includes immediately cleaning and dressing any open wounds, as the odor of damaged tissue is a primary attractant for female flies seeking egg-laying sites.
For personal protection, using insect repellent and wearing long-sleeved clothing in endemic areas helps reduce the risk of fly contact. Management of a suspected infestation requires swift action and professional intervention. Medical or veterinary removal of the larvae is usually required, often involving mechanical removal or debridement of the affected area. Antiparasitic medications like ivermectin may also be used to eliminate the larvae.