Maggot therapy comes to the rescue
Larvae successful in insect bite case
The practice of using sterile maggots for treating chronic wounds is not likely to sweep throughout the caregiver community overnight, but clinicians internationally have taken an interest in - and found promising results with - the unconventional treatment. (See Wound Care, February 1997, pp. 13-15.)
Following is a case history from a hospital in Wales that describes in detail the process and success of a course of maggot therapy (also referred to as larval therapy) to treat an infected insect bite that caused an extensive leg ulcer.1
The patient, a 66-year-old woman with a history of hypertension and rheumatoid arthritis, had previously received bilateral total knee replacements, which restored a reasonable degree of mobility. During a Mediterranean vacation, an insect bit her on the left foot. The bite became infected, and the patient's leg swelled to the knee and reddened. After admission to a local hospital, she received intravenous antibiotic therapy, but her condition deteriorated. Cellulitis reached her groin, and the area below her knee became covered with blisters.
Extensive surgical debridement - without any anesthetic or analgesia - was performed, causing the woman great pain and distress. The wounds were then cleaned with water. A silvadene dressing was applied and was renewed daily. The patient flew home to the United Kingdom 10 days later.
Back in the UK, the patient was admitted to the medical unit in the University Hospital of Wales in Cardiff. By now, her wound had become necrotic in a large area on the posterior aspect of her left calf, extending from the knee to the Achilles tendon. A smaller wound above the medial malleolus similarly contained a thick layer of slough. The surrounding skin was red and the leg was very painful. Blistering marked the patient's left thigh all the way up to her groin.
Both wounds were treated with a hydrogel and covered with a secondary dressing. A dermatologist diagnosed cellulitis and lymphangitis (inflammation of the lymph vessels). Intravenous antibiotic therapy was administered, consisting of benzylpenicillin and flucloxicillin. The wound on the outer aspect of the leg was then dressed with an alginate dressing, and the wound on the inner aspect was dressed with a hydrogel containing metronidazole. Six days later, both wounds had improved only slightly.
After nine days, the patient received oral antibiotic therapy, which was discontinued after only four days because the patient tolerated the drug poorly. Intravenous antibiotics were begun again. A biopsy of the wound was taken to exclude the possibility of pyoderma gangrenosum.
Considering the options
The possibility of larval therapy was considered after two weeks post-admission. The patient agreed, provided she did not have to see the maggots. Her qualms led to initial larval treatment only of the wound on the medial aspect of her leg.
Skin surrounding the wound was first protected by strips of a hydrocolloid sheet approximately 2 cm wide. About 150 sterile larvae were gently rinsed out of the container in which they were supplied and placed on a piece of sterile net, which was trimmed to overlap the edges of the wound by about 1 cm. The net was attached to a hydrocolloid dressing with adhesive tape ensuring the edge was completely sealed to prevent the maggots from escaping.
The hydrocolloid frame provided a skin-friendly base for the sterile net and protected the skin around the wound from the action of proteolytic enzymes produced by the larvae. It also stopped the larvae from migrating onto intact skin, where they might cause a tickling sensation.
Gauze swabs were moistened with sodium chloride solution 0.9% and placed on the outside of the net to ensure that the maggots did not dry out. The dressing was then covered with dressing pads secured into place with a bandage. After 48 hours, the larvae were removed and the wound was reassessed. Some of the maggots had died, but the amount of slough on the wound had diminished noticeably. The remaining maggots were washed off the wound with sodium chloride solution 0.9%. A second batch of larvae was applied, and this time a batch also was introduced into the second wound. Again, they were left for 48 hours.
Removal of the outer dressings revealed a marked reduction in the amount of slough. Another batch of larvae was applied, and intravenous antibiotics were discontinued and replaced with an oral elixir, which the patient tolerated well.
After another 48 hours, a significant number of larvae had died on both wounds, but those that survived had further reduced the amount of slough and necrotic tissue present. Twenty days after admission, following a third cycle of larval therapy, the wounds showed considerable improvement. The patient had also overcome much of her initial dislike of the creatures. Unfortunately, however, she developed a further episode of cellulitis which necessitated a five-day course of intravenous antibiotic therapy.
After four more rounds of larval applications, the treatment was discontinued. She had been hospitalized for 30 days. The wounds were completely free of slough, with evidence of much new granulation tissue present. Conventional dressings were then applied to continue the healing process. Three days later, antibiotic therapy was discontinued. The patient's leg was pain free with no erythema present in the surrounding skin. Conventional treatment continued until the patient was discharged, although this was delayed for a week because of a flare up of her rheumatoid arthritis. Six weeks after discharge her wounds were virtually closed.
The author of the case history reached this conclusion: "The larvae made a major contribution to the successful treatment of this patient, removing the slough that formed a barrier to healing and a potential source of infective organisms. In this particular instance, however, debridement was slower than anticipated because of the unexplained high mortality rate of the maggots during the early stages of treatment."
Reference
1. Chaffey R. Case study: Larval therapy for an infected insect bite. World Wide Wounds October 1997. http://www.smtl.co.uk/World-Wide-Wounds/
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