Sterility is the principal factor for the success of MDT. Sterile larvae are used to avoid contamination, for this purpose larvae are bred in sterile and moist environment. Optimum moisture level and adequate supply of oxygen to the maggots in the wound helps to hasten the process of healing. Formerly, it was considered that the numerous microscopic hair-like projections on the bodies of larvae and a pair of mandibular hooks assist in the debriding activity along with their movements
LARVAE HAVE been used for wound healing since centuries. Ambrose Paré was the first to discover the benefits of larval therapy in 1557. Baron Larrey, a physician of Napoleons army, reported the augmented granulation by the maggots in wounds. American Civil War was the time when Jones and Zacharias performed maggot therapy clinically. Afterwards, William Baer used sterile maggots, and chances of maggot-induced infection were greatly controlled. During the decade of 1930, for infected and chronic wound treatment this technique gained currency in Europe and North America. In 1940s, advancement in medical science and fame of antibiotics diverted the attentions of medical staff from MDT. Few decades later antibiotic resistance flared across the globe, rendering many antibiotics less or ineffective. This again bumped MDT in scientists and medical professionals mind as the appropriate treatment in chronic wounds.
In our world, where medicine and treatment are at their bloom, new researches and inferences are underway. But at the same time, number of cases suffering from chronic wounds accredited to diabetes and peripheral vascular disease are also increasing with every passing day. A chronic wound is the one, which is halted at the inflammatory stage, characterized by the presence of necrotic tissue, debris and infection. These chronic wounds require intense care and are expensive to treat. As far as the treatment of wounds is concerned, it involves debridement and dressing. Debridement of wound encompasses empirical steps as removal of necrotic tissue, exudates, alien substances and microorganisms; on the other hand dressing checks the contamination of chronic wound site. In comparison to surgical intervention, MDT has proven to be effective, speedy and cheap procedure for the treatment of wounds.
Lucilia Sericata is well known all over the world, most abundant in continents of Africa and Australia. Moreover, its habitat is moist and warm climates. It has the typical life cycle of flies, comprising of egg, maggot, pupa and adult. The eggs are laid in meat, fish, infected wounds, dung and the dead bodies. Its importance is undeniable in medical and veterinary treatment as its larvae are being used in MDT. Larvae (1-2 mm) feed on dead and necrosed tissue of the wound, grow and mature in approximately 4-5 days. Upon maturation and just before pupation they measure 10 mm in length.
Sterility is the principal factor for the success of MDT. Sterile larvae are used to avoid contamination, for this purpose larvae are bred in sterile and moist environment. Optimum moisture level and adequate supply of oxygen to the maggots in the wound helps to hasten the process of healing. Formerly, it was considered that the numerous microscopic hair-like projections on the bodies of larvae and a pair of mandibular hooks assist in the debriding activity along with their movements. Recently, three types of excretory/secretory (ES) proteolytic enzymes have been reported to be helpful in addition to the above-mentioned factors in degrading the extracellular matrix components (e.g. laminin, fibronectin) of wounds. Moreover, maggot ES products contain antibacterial substances, causing inhibitory effects on the gram positive and gram-negative bacteriae, such as Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Another factor causing the development of an unfavorable environment for the bacterial growth is the elevated pH due to ammonia excretion by maggots. Larvae effectively remove necrosed and dead tissue without any damage to the adjacent healthy tissue. This debriding action stimulates tissue granulation and decreased unpleasant odors brought about by such infections.
A variety of chronic wounds have successfully been treated using MDT, including surgical wounds infected with Staphylococcus (S.) aureus, chronic venous ulcers, diabetic ulcers and pressure ulcers. In a research conducted on diabetic foot ulcers, complete debridement was achieved in 4 weeks. Diabetic ulcers, Venous ulcers, Post-traumatic wounds/ulcers, Pyoderma gangrenosum, Grossly infected toe, osteomyelitis, infected wound after forearm replantation, wound infection after breast surgery, infected gun-shot wound, malignant wounds, burns, non-healing surgical wound, methicillin-resistant S. aureus-infected wounds can be corrected by the use of MDT. Bedsores and ulcers in rabbits and pod dermatitis in sheep have been treated by this therapy and speedy healing was observed.
In horses, MDT is particularly an effective treatment in pus-producing infections, frequently resulted by rasping of the working gear, osteomyelitis, sub-solar abscesses leading to osteomyelitis, post-surgical treatment for puncture wounds, canker and non-healing ulcers of hoof. Conclusively, MDT not only debrides but also prevents secondary bacterial infections and beholds a promising future and ray of hope for the patients suffering from chronic wounds. However, MDT is contra-indicated in dry wounds, as larvae need a moist environment. MDT is not advised in open wounds of body cavities and wounds close to large blood vessels. Mild discomfort has also been reported during the therapy.
Excessive pressure of dressing may kill the maggots, which results in uneven wound debridement. Major hindrance in routine application of MDT is its poor acceptance by health-care professionals and patients probably due to social and cultural beliefs. So, inspite of feasibility and effectivity of MDT for wide range of chronic wounds, which are non-responsive to conventional therapies, it is not much accessible due to lack of sterile breeding sites for larvae in the developing countries. However, we may hope that rearing of sterile larvae would be possible by the entomologists and veterinary professionals of Pakistan, which can be helpful to apply this wonderful technique in the field of veterinary medicine.
The writers are attached with the Department of Parasitology, Faculty of Veterinary Science, University of Agriculture, Faisalabad.