Misunderstood Maggots

Just about every veterinary technician who has been in practice for more than a year has a maggot story to tell. The response is almost universal: eeeuuuwwww. You get that shudder up your spine and the urge to hurl just thinking about them. Unfortunately, maggots are a fact of life where animals are concerned.

We wish that every animal had decent living conditions, regular grooming, and never suffered an untended wound. That is not the case. Vet techs who work in mixed or large-animal practices or in shelters see more than their share of maggots. Outdoor animals are exposed to flies all the time. When they become debilitated or wounded they turn into fair game.

Even loved pets that live mainly indoors can become unwilling hosts for fly larvae under the wrong circumstances. Neglected grooming, hot spots, stool matted in fur, a draining anal gland abscess — these are all minor problems that can quickly become disgusting if a fly decides to lay her eggs there. Yuk! Flesh-eating maggots.

Who would think that these gag-inducing larvae might actually be beneficial in certain medical conditions?

Believe it or not, maggots have been used for centuries to treat wounds. Their ability to debride necrotic flesh comes from the proteolytic enzymes they secrete. These enzymes break down dying tissue but leave healthy tissue intact. Maggot therapy also increases fibroblast migration to the wound, which helps speed up healing.

Photo courtesy of Monarch Labs

Medical maggots are the larvae of green bottle flies (blowflies). When used correctly in a wound they inhibit the growth of several common and difficult bacterial organisms, particularly Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. This makes maggot therapy especially useful when drug resistance has become an issue.

The United States Food and Drug Administration regulates the production and use of medical maggots to ensure that patients are helped rather than harmed. The maggots are carefully prepared, packaged, and shipped by a licensed laboratory. They are used in both human and veterinary medicine. Wound preparation and maggot placement must also be carefully controlled and timed. Because the tissue involved is already devitalized, the process is painless.

So from now on, don’t be so hard on the little critters!

Detailed directions and photos can be found in the article “A Fly in My Ointment: Maggot Therapy,” published in the April 2012 issue of the NAVC Clinician’s Brief. The authors were Karen Tobias, DVM, MS, DACVS, & Danielle Browning, LVMT, of the University of Tennessee.