Maggots in Wounds: Insights into Larval Therapy
What is Larval Therapy?
Larval therapy uses living fly larvae or maggots to debride open wounds, which means removing dead or decaying tissues that may have been infected or severely damaged. The importance of physically removing these tissues is to promote faster wound healing and to prevent the spread of infection through blood. The larvae do this effectively by munching on the dead tissues, leaving healthy tissues to heal and granulate, that is form new tissues that fill up the wound.
How Larval Therapy Began
Although scientific studies about the use of maggots in wounds only commenced after World War I, their benefits were observed centuries ago by different cultures like the Mayan Indians and Australian aboriginals. For example, the Indians would apply dressings made of beef blood that had been exposed to the sun and later covered with maggots.
Military doctors in medieval times observed that open wounds on soldiers which could not be effectively treated with medicines healed when infested with maggots. Many lives were saved because infections were controlled within days despite the lack of medicines and supplies during war.
Between the 1920s and the 1930s an American orthopedic surgeon named William S. Baer conducted scientific studies on the use of larval therapy on soldiers and patients who suffered from different types of wounds. He introduced maggots into the open lesions of 21 patients with chronic osteomyelitis and within two months all the lesions of all the patients had healed.
Following publication of Baer’s results larval therapy spread throughout the United States and Canada and larval therapy was included in the treatment of other conditions such as breast ulcers and abscesses, osteomyelitis, burns, ulcers from cancer and subacute mastoiditis. However, it diminished in the 1940s as penicillin and other antibiotics occupied medicine’s center stage.
Renewed Interest in Larval Therapy
Although the use of antibiotics has revolutionized the treatment of many types of infections, new problems have also emerged with their improper use and the emergence of resistant strains of micro-organisms. The over-use of broad spectrum antibiotics to treat mild bacterial infections or their misuse for treating viral infections has led to the development of subspecies of pathogens that do not respond to antibiotic treatment, leading to non-healing wounds and spread of infection.
Consequently there has been a renewed interest in the use of larval therapy to heal wounds which has been spearheaded by Dr. Ronald Sherman, a Californian physician who bred green bottle flies to produce larvae at the Veterans Affairs Medical Center. He sterilized the larvae and used them to treat non-healing ulcers in successful trials in 1989. Since then the larvae have been marketed as Medical Maggots. The use of larval therapy for healing wounds has been granted permission by US FDA in 2004, and is also being practiced in other countries in Europe and Asia.
How Maggots are Applied to the Wound
Only larvae of specific families of flies such as Lucilia sericata (common green bottle fly) and Phormia regina (black blow fly) are used for therapy. These are treated and sterilized in laboratories, packed in vials and sold under prescription.
A hydrocolloid dressing with a hole similar to the size and shape of the wound is placed over it and serves as a base for the outer dressing. Next, larvae measuring one to three millimeters long are placed over the wound, approximately ten maggots per square centimeter of wound area, and then covered with a nylon net and an absorbent pad for the exudates. The larvae are allowed to munch on the dead wound tissues for three days while only the absorbent pad may be repeatedly changed.
The dressing may be removed and wound cleaned with sterile saline solution after the third day. A fresh batch of maggots may be applied if necessary. These may be done with or without the use of conventional antibiotics.
Advantages of Maggot Therapy
The renewed interest in larval therapy is brought about by the benefits it has over conventional treatments:
- It is effective – necrotic (dead tissues) are successfully removed by the scratching and poking action of the “mouth hooks” (not teeth) of the maggots.
- It is safe – the larvae are prepared in a sterile manner in pharmaceutical laboratories and are sold as medical grade maggots.
- It is easy to apply – there is no need for a surgeon to apply the maggots and the dressings; these can be done at home by a therapist and still be as effective as surgical debridement.
- It is affordable – less expensive than surgical debridement or completing a cycle or more of antibiotics and wound dressings.
- Faster wound healing – with the removal of dead tissue, infection is prevented and the wound is allowed to produce new tissues with improved circulation.
Disadvantages and Misconceptions
- Fear of pain – pain during treatment may be felt if the patient has been experiencing pain prior to it. However, this may be given appropriate remedy with suitable pain medications. The pain may be due to the crawling, scratching and poking of the maggots; this sensation may not be felt by other individuals who did not experience pain before treatment.
- Maggots are perishable – the larvae have to be used within 24 hours of delivery.
- Other misconceptions – patients may have misapprehensions such as maggots turning into flies or maggots burrowing inside healthy tissues, although these may be dispelled with proper information from a doctor. Maggots need oxygen to survive and will not burrow deep into the tissues where they would be deprived of oxygen. It would also take about two to three weeks for them to mature into flies, so this will not occur within the couple of days they are used for the treatment.
So for non-healing or resistant wounds, abscesses and ulcers, let the maggots munch!
Larval Therapy: A Review of Clinical Human and Veterinary Studies, http://www.worldwidewounds.com/2000/oct/Janet-Hinshaw/Larval-Therapy-Human-and-Veterinary.html
Maggot Debridement Therapy (MDT), http://www.medicaledu.com/maggots.htm
Picture credit: Image released into the public domain by the National Institutes of Health