Use of sterile maggots to treat panniculitis in an aged donkey

Maggots successfully used to clean elderly donkey’s wound

source: N.J.Bell and S Thomas
Veterinary Record vol 149 no 25 December 22 2001
starts p768, 3 pages long

Sterile maggots have successfully been used to clean a wound affecting an elderly donkey, which could not be treated using conventional methods. The donkey developed panniculitis, following a skin wound. Bacteria found in the wound included Pseudomonas aeruginosa that was resistant to a number of drugs, Escherichua coli, and Streptococci.

Maggots secrete antimicrobial enzymes, which may help with healing, and they have been used to clean wounds in humans. Some 150 common greenbottle larvae were used in this case, or 15 larvae for each square cm of exposed tissue. Nylon gauze kept the maggots in place, and the gauze was glued to the donkey’s skin with cyanoacrylate adhesive spots. A gauze swab soaked in saline solution was also taped on the mesh, to provide good conditions to the larvae. The wound was examined after three days, and the larvae replaced, with intervals between applications lengthened to five days.

The donkey was more than 30-years-old, and the cause of the injury was unknown. The wound had started to heal, but there was a discharge from the centre. Surgery failed to clean the wound and allow it to heal fully, and it was feared that the donkey was too old to undergo repeated surgery with general anaesthetic.

Sheep and rabbits do not appear to be able to inactivate the enzymes that these larvae secrete, and they can suffer from myiasis, a potentially fatal condition, from greenbottle larvae. Humans, however, can inactivate the enzymes, and equids also appear to be able to do so. The larvae in this case only ate diseased tissue, and dropped off the donkey once there was no more diseased tissue for them to eat. A total of six applications were used, with the treatment ending when the larvae not longer had enough to eat. Other types of larvae, such as screw-worm larvae, can harm both humans and equids.

Surgery is often difficult in these cases because it is not always easy to tell the difference between diseased and healthy tissue, and antibiotics may not work, especially if blood circulation is poor in the affected area. The donkey in this case appeared to benefit from a reduction in pain from pressure on the wound area, quite early in the treatment, and did not seem aware of the larvae. There was no need to sedate the donkey, which became more comfortable as there was no need for injections, and the pain eased. A reduction in stress can help wounds to heal.

There were some minor problems, such as larvae being delayed in the post, and arriving dead, or not taking, possibly due to contact with a wound cleaning agent, and the repulsion felt by some staff caring for the donkey. This treatment for severe panniculitis affecting an elderly donkey was, however, both effective and safe, and had a number of advantages over the more conventional options such as antibiotics and surgery.