After many decades of research, blow flies are being used to heal previously untreatable wounds.
Three of the big groups of pest flies are the ‘filth’ flies, the ‘flesh’ flies and blow flies. Filth flies get their name from their close association with decomposing organic material such as garbage and faeces. Flesh flies (Sarcophagidae) get their name from their behaviour of laying eggs or live young on open wounds of animals. But both flesh flies and blow flies will also lay eggs on carrion and decaying flesh. All three groups of flies are considered ‘dirty’. However, one species of blow fly, the common green bottle fly, is actually being used to clean problematic wounds in a treatment called maggot therapy.
The adult female green bottle fly, Lucilia sericata, is attracted to decomposing flesh, where it lays its eggs. The maggots feed on the decomposing flesh by excreting digestive juices onto the infected tissue and sucking up the resulting liquid. Once they are ready to pupate or have run out of food, they leave the host. This behaviour of fly larvae feeding on a live host is called myiasis. This behaviour has now been harnessed to promote healing in chronic wounds and sores in humans.
For centuries it has been observed that the wounds of soldiers that become infested by maggots appear to heal better than uninfested wounds. After World War I, William Baer started experimenting with the use of maggots for wound management at John Hopkins Hospital in Baltimore, USA. It didn’t really take off, as antibiotics appeared to deal with any potential wound infection and therefore allow effective healing. However, with increasing antibiotic resistance appearing in the 1980s, the use of maggot therapy to clean and promote healing in problematic wounds started to gain traction.
In maggot therapy, L. sericata larvae are place on the wound, which is then wrapped for approximately 48 hours. The larvae then feed on the necrotic (dead) tissue and bacteria that occur in an infected wound. It may sound gross, but for those with chronic wounds it is often the only solution to avoid amputation or worse. Not only do the larvae remove the necrotic material, but they also secrete antimicrobial enzymes and stimulate healing of the wound. It may take more than one treatment to remove all the necrotic material.
Of course, as a therapy, medical professionals do not use naturally occurring flies and maggots, as they could potentially introduce other diseases due to the microbes they carry. The larvae used in maggot therapy are surgical-grade fly larvae bred from sterilised eggs in approved laboratories.
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