Debriding Chronic Wounds With Larval Therapy: The New Answer for Biosurgery in the Outpatient Wound Clinic?

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Of all the available debridement methods, biosurgery (including larval therapy) remains the most underutilized in the outpatient setting. This is true despite its being proven highly selective,¹ its potential to reduce amputation rates² and the need for antibiotics,³ its ability to remove Methicillin-resistant Staphylococcus aureus (MRSA)⁴ and biofilm,⁵ and its impact on increased healing rates and healing times.⁶ That said, all of these benefits can be achieved within an average of 1-3 treatments.^7-9 Introduced into modern medicine in 1929 by Dr. William Baer of Johns Hopkins University Hospital, larval therapy utilizes the living larvae of the green bottle fly (the Lucilia sericata) to debride nonhealing, chronic wounds. The traditional application method of this therapy received approval from the U.S. Food & Drug Administration in 2004, but it is often adopted as a “treatment of last resort” when all other healing efforts have failed. This article will discuss the process of larval therapy and offer patient case study examples in an attempt to educate wound care clinicians on this modality and perhaps reverse the stigma associated with the perception that use of a living organism will have negative effects that could prevent wound healing.

Traditional Larval Therapy

The traditional application method (known as loose or free-range larvae) has a complex application process that requires larvae to be applied directly to the wound at a dose of 5-8 larvae per/sq cm. An external, cage-like dressing is then built around the wound to contain the larvae to the treatment area. This application method is time-consuming, does not guarantee accurate dosage, and risks larvae escape. It has been found that larvae escape the wound dressing in 43% of cases,¹⁰ which would pose a challenge when initiating the therapy in an outpatient setting due to the infection-control risk in the patient’s home (and would certainly be a factor in reducing patient consent).

Contained Larval Debridement Therapy

BioBag^® (BioMonde,^® Gainesville, FL), a patented, natural larval therapy product designed for the debridement of nonhealing skin and soft tissue wounds, is an example of a simple, yet effective, concept. A heat-sealed porous polyester bag that contains larvae in five dressing sizes, each with a precalculated dosage based upon the area of the wound to be treated (see Table 1), BioBag offers an application that is quick and removes the need to count larvae for a correct dosage. The larvae remain contained within the bag for a treatment duration of four days (see Figure 1), which avoids the need for handling or touching of the larvae (although they do no bite). The larval enzymes pass through the porous design of the containment dressing to allow the larvae to effectively debride at an efficiency as precise as if they were uncontained and directly on the wound bed.¹¹ This new delivery vehicle for the larvae eliminates the risk of larval escape, and, although the updated design is primarily to ensure the larvae remain on the wound bed for the full four days, this modality also reduces time needed at the bedside for application and removal. Additionally, this method has been found to be a quicker procedure than sharp/surgical debridement, since the application occurs just as with a conventional dressing. The new containment method also opens the door to allow patients and/or their caregivers to manage the dressing at home without fear of larval escape or management of a complex dressing change. The steps of caring for the sealed bag and outer dressing change can be easily followed while minimizing the costs associated with repeated clinic visits. 

Mode of Action

Larvae produce secretions that include proteolytic enzymes (enzymes that dissolve protein) and break down the devitalized tissue and bacteria into a liquid (or semiliquid). The larvae then ingest (suck up the nutrition via a vacuum action) and remove the liquid/semiliquid from the wound. Larval secretions contain enzymes and proteases such as trypsin, chymotrypsin 1, collagenases, nuclease, lucifensin, and seratacin, which have antimicrobial, anti-inflammatory, and cell-stimulating properties.¹²

Antibacterial Action

Reducing the risk of infection and sepsis while balancing the overuse of antibiotics for outpatient wound care is critical. Larvae have several actions against microbes present in the wound, including planktonic bacteria, mature biofilm, and fungi. This includes MRSA, S. aureus, and Pseudomonas aeruginosa. Evidence is available to show that larvae physically remove both gram-positive and gram-negative bacteria, which they destroy within their gut. The larvae create an alkaline wound environment (pH 8-8.5) — an unfavorable environment for bacterial growth — and the larvae’s presence on the wound bed stimulates the production of exudate, further flushing bacteria from the wound.

Suitable/Unsuitable Wound Types

BioBag is indicated for the debridement of necrotic, nonhealing wounds. Rapid results are achieved in wounds with soft, moist tissue due to the larvae’s mode of action. Table 2 above contains a list of wound types that contained larvae can be used to treat. The main contraindications are based upon a risk of bleeding, an allergy to polyester (or fly larvae), or a wound environment/location that will not support larval viability, such as areas that are unable to be offloaded. Known side effects include irritation of the periwound and increased pain. 

Inventory, Sizing, Application

BioBag is not a stock item and should be ordered in advance for each patient. A medical device that must be ordered by a licensed clinician, it should be applied within 24 hours of receipt because viability is reduced after this time. Consideration should be taken when ordering for nonadherent or non-arrival patients because the larvae cannot be returned after dispatch — another suitable patient must be sought. The BioBag (or multiple bags depending on the wound size) requires direct physical contact with the wound bed to be effective and should overlap onto the wound margins to allow the larvae to treat closed, non-advancing wound margins or areas of maceration. If the wound has any depth, this measurement should be added to the initial measurement to ensure complete coverage. It is not possible to treat part of a wound, as no other treatments or dressings with an active ingredient can be used concurrently because this could affect larval viability. Application should be complete in 5-10 minutes in order to reduce patient treatment times (application steps outlined in Table 3). BioBag can be applied by any wound care practitioner and can be easily managed by the patient or caregiver at home, as it is applied and managed just as with any conventional dressing. 

Reassessment & Disposal

BioBag treatment should be discontinued when the wound is no longer classified as nonhealing (ie, the wound is progressing and no longer requires debridement). The treatment can remain in place until wound progression is visible with the presence of granulation tissue and advancing wound edges. Larval therapy is effective at debriding a wound in an average of eight days (1-3 treatments). Each treatment remains on the wound for up to four days (96 hours), and on Day 3 the wound should be assessed for need of potential further application. Due to the contained nature of the bag, it is easy to dispose of in the outpatient clinic or at the patient’s home. In the clinical setting, it is placed in a red bag and treated as standard biohazard waste or is placed in a sealable plastic bag and placed in the regular household trash in the patient’s home.

Medicare Patient Case Studies

The first case to be profiled describing the use of BioBag in the outpatient setting is an otherwise healthy 96-year-old female living with a nonhealing necrotic wound post-radiation of squamous cell carcinoma of the left anterior lower leg. The wound remained nonhealing for 11 months and (at a previous facility) was treated with hyperbaric oxygen therapy (HBOT), Dakin’s solution, and Manuka honey. It remained 100% sloughy, malodorous, and highly exuding — leading to the patient’s self-referral to a new facility, where she received sodium oxychlorosene and the BioBag was initiated. Three treatments were applied; the first two were applied in succession and the third treatment was applied after a gap of four weeks. Prior to the first application, the slough was moist, thick, and adherent Figures 2 and 3), and there was a large portion of exposed tendon and tibia. BioBag was applied with the knowledge that the selective larvae secretions would not damage the tendon or bone if they were viable. Tissue improvement was visible after the first application (four days), with new granulation tissue present (Figure 4). After completion of the third BioBag treatment (Figure 5), the malodor had improved and the wound had progressed enough to allow treatment to continue with a collagen powder, negative pressure wound therapy (NPWT), and then a split-thickness skin graft. At the time of this writing, the wound had achieved 80% closure. 

The second case study involves a 75-year-old male with a history of mild to moderate peripheral artery disease and renal transplant. (He was also immunocompromised related to chronic antirejection medications including Prograf^® [Astellas Pharma Inc., Northbrook, IL] and prednisone.) He presented to the emergency department with altered mental status and pain in his right leg two days after pulling weeds. He was noted to have an abrasion with redness of the right lateral malleolus. His condition rapidly declined that night, requiring intubation, vasopressors, and surgical debridement. The diagnosis was necrotizing fasciitis due to direct water inoculation of Aeromonas hydrophila. During his initial visit to the clinic following hospital discharge, the patient was noted to be in extreme pain. The wound was 100% slough with exposed muscle, tendon, and bone (Figure 6; prior to first BioBag application). There was full thickness skin necrosis over just under half of the lower leg, extending distally over the Achilles tendon, wrapping around medially and laterally largely over the gastrocnemius muscle. The plastic surgeon’s goal was to get enough granulation tissue for a below-knee amputation, otherwise an above-knee amputation would be needed. Due to the patient’s age, the decision was made that he would have a better chance of ambulation with a below-knee amputation. His circulation was assessed to identify the likelihood of healing, and it was identified that he should have adequate arterial supply to heal his wound (and no vascular intervention was needed). Two applications of BioBag were used with a 10-day gap between treatments. Significant debridement was achieved after one four-day treatment (Figure 7). The wound proved to be clean enough to commence NPWT and HBOT six days after completion of the second BioBag treatment (Figure 8 ). The wound continued to progress over the course of the ongoing treatment, and total closure of the wound was achieved after split-thickness skin grafting and compression therapy (Figures 9-11 ). Not only was planned amputation avoided for this patient, but debridement with contained larvae caused no pain during the treatment, whereas the patient required a large amount of lidocaine before debridement with ultrasonic-assisted debridement and sharp/surgical debridement. 

Reimbursement Notes

As highlighted with the two patient case studies presented in this article, BioBag can be used in the outpatient setting to deliver cost-saving care for nonprofitable/costly or private-insurance patients with the aim to speed the healing process, prevent hospital admission/readmission, and ultimately improve quality of life. However, despite larval therapy being an old concept, BioBag, as a new product to the market, does not yet have a Level II Healthcare Common Procedure Coding System code. The American Medical Association recommends reporting the use of BioBag (larval therapy) within the procedure of nonselective debridement (Current Procedural Terminology code 97602) and reporting the use of BioBag as an additional medical supply using miscellaneous supply code 99070. The cost of BioBag is partially covered under the provider fee available for the nonselective debridement procedure, although there is no physician fee associated with this procedure. It is not necessary for a physician to apply BioBag, but rapid outcomes can be achieved by applying it onto the wound at the bedside immediately after sharp/surgical debridement. This treatment option has the potential to speed the debridement process and is indicated if the wound isn’t actively bleeding at the time of application and a local anesthetic is not present in the wound. Most major private insurance companies have been known to approve the cost of BioBag (with individual patient preauthorization), and, due to potential improvement and increased speed of outcomes, patients may consider funding the product cost themselves.

Editor’s Note: The information reported in this article does not reflect the thoughts or opinions of Piedmont Health System. The patient data were not altered for the purposes of this publication and have been reported in a factual manner with the appropriate consents in place. The author has no conflicts of interest to report.

Judith Turner is on staff at Piedmont Outpatient Wound and Hyperbaric Center, Atlanta, GA.

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