Maggot Therapy. Bio 3323 Entomology. Teacher : Jon G. Houseman. Department of Biology. University of Ottawa

Transcription

1 Maggot Therapy ` By Bio 3323 Entomology Teacher : Jon G. Houseman February 9, 2004 Department of Biology University of Ottawa

2 Maggot Therapy BBC journalist Georgina Kenyon describes the new fad in British hospitals of using fly larvae for cleaning non-healing infected wounds in her article entitled Maggot medicine gains popularity. According to Kenyon, the maggots are one of the most effective ways of treating wounds infected by drug-resistant bacteria and non-healing leg ulcers. The four-page article explains the positive effects of using maggots, very briefly touching how they feel on the body and how they disinfect the wound. Kenyon doesn t mention the history behind this bizarre treatment but did write almost a page on how Alan Hughes, a 60-year-old patient of Dr. Walker, thinks they re great just like a maggot sandwich! History The use of maggots for wound cleaning was first observed on the battlefield during the Napoleonic, American Civil and World Wars where military surgeons observed that the wounds of soldiers infected with maggots healed better than soldiers with similar wounds not infested (Beasley and Hirst 2004). They were often used in the 1920s and 30s in North America and Europe before the emergence of effective antibiotics and lost it s popularity with the increase availability of antibiotics in the 1940s (Beasley and Hirst 2004). In the 1990s, maggot therapy reappeared due to antibiotic-resistant bacterial strains (Handwerk 2003). Today, more and more doctors are using maggot therapy also called biosurgery or Maggot Debridement Therapy (MDT) but a lot of them are still very sceptical.

3 How they work Kenyon very briefly explains how the maggots secrete proteolytic enzymes to break down dead tissues but she neglected to mention how they disinfect the wound. Maggots work by secreting proteolytic enzymes such as collagenase, trypsin-like and chymotrypsin-like enzymes that will catalyze the breakdown of macromolecules on the wound surface, which will then be ingested by the larvae (Beasley and Hirst 2004). In other words, the insect will first dissolve dead tissue by secreting digestive juices and then they ll ingest the liquefied tissues infected with bacteria. As they feed, they disinfect the wound by killing the bacteria as they pass through the digestive tract. They also secrete antibacterial compounds produce by the gut and finally but not the least they will initiate the formation of a serous exudates by the wound, cause by their movement, that promotes wound cleansing and dilution of bacterial concentration (Beasley and Hirst 2004). Kenyon wrote that the larvae chosen for medical purposes are usually of the green blow fly variety (Lucilia (Phaenicia) sericata) because this species only feeds on necrotic tissue. This is true but they are also the larvae of choice because they don t invade internal organs and they act quickly on the wound. They are easy to sterilize and will also change the ph of the wound from acid to alkaline making the wound a less desirable environment for bacteria (Brocklesby 2002). The increase in the ph is due to the ammonia and other agents found in the secretion of the maggots (Mercola 2004). Other varieties

4 such as Cochliomyia macellaria, Chrysomya megacephala and Lucilia cuprina cannot be used as they cause malign myiasis although L. cuprina has already been used with success which means that we might see other success stories in the near future with the other two types (Brocklesby 2002). Kenyon mentions that the maggots used in hospitals are sterile but what are the consequences if the hospitals fail to deliver? It s important to understand that serious infection complication can result if the maggots are not free of pathogens. A recent study showed that when maggots used in debridement therapy were not germ-free, 5 out of the 24 patients observed (21%) developed a bloodstream infection due to the contaminated maggots (Nuesch and Ilg 2002). The sterilization process is explained in details in the article written by Nuesch and llg. A 20% glucose solution and fresh bovine liver is fed to the maggots in the sterilization process to induce oviposition (Nuesch and llg 2002). Oviposition is important in larvae because they lack teeth and in order to break down tissue they need a pair of hooks (Beasley and Hirst 2004). Maggots are only considered as an alternative therapy when two or three other conventional medical or therapy fails. They are mostly applied to foot and leg ulcers, burns and post-operative wounds that are infected. Five to ten maggots will then be applied on each square centimetre of a wound with a protective dressing over it (Handwerk 2003). The dressing needs to be light enough to permit the entry of air so the maggots don t suffocate and also because the necrotic tissue should be able to drain out through the dressings (Sherman 1996).

5 When the maggots are first applied they are approximately two millimetres in size and at the time of removal, 48 to 72 hours later, they are about ten millimetres (Handwerk 2003). There is no chance of the larvae turning into flies in your wound since it takes up to seven days to pupate (Scott, 1997). No feeling? Kenyon mentions in her article that most patients do not report any feeling of the maggots on their skin. It is true in most cases but some patients do experience a tickling or itching sensation or feel the maggots crawling on their skin and some feel pain. The pain can be related to the increase in the larvae s size explains Handwerk, which makes it more difficult for them to squeeze into tight crevices. Another explanation, also due to an increase in their size, is that they crawl over the nerves, which results in pain. The pain can be controlled with light medication or by the removal of the maggots. Use of maggots in treating wounds with hospital-acquired pathogens Kenyon wrote about the efficacy of maggots in treating wounds infected with Methicilin-resistant Staphylococcus Aureus (MRSA) antibiotic-resistant bacteria causing infection that could lead to pneumonia in some cases. An in vitro study done by Dr. Steve Thomas, Princess of Wales Hospital, Bridgend, UK, showed that maggots kill or inhibit the growth of S Aureus and of group A and B streptococci but no effect was observed against Escherichia coli and Proteus spp (Mercola 2000). Thomas also treated five lesions infected with MRSA and of the

6 five, all came back MRSA-negative, but these results were never published (Mercola 2000). Thomas also quotes that these findings are consistent with clinical observations that maggots can combat infections in a variety of wound types, including those infected with antibiotic-resistant strains", (Mercola 2000). But after an elaborate study done by Nuesch & al, they concluded that yes they (maggots) may have a particular role in eliminating MRSA an other acquired hospital pathogens, although large scale randomized, controlled trials with adequate follow-up are needed to confirm these suspicions. In conclusion, the author mentioned some important facts of MDT in her article but always failed to give references that would give credit to her writing. Kenyon put all the emphasis on how some patients felt about maggot therapy and almost nothing on the scientific aspect of the treatment.

7 Bibliography Beasley, W.D., Hirst, G. Making a meal of MRSA the role of biosurgery in hospital-acquired infection Journal of Hospital Infection 56 (2004): 6-9. Brocklesby, Sarah. MRSA, macrophages and maggots (Clinical Review). The Diabetic Foot 22 March 2002 < Handweck, Brian. Medical Maggots Treat As They Eat. National Geographic 24 October 2003 < Mercola, Dr.Joseph. Home page. 15 October 2000 < Nuesch, R., Rahm, G., Rudin, W., Steffen, I., Frei, R., Rufli, T., Zimmerli, W. Clustering of Bloodstream Infections during Maggot Debridement Therapy Using Contaminated Larvae of Protophormia terraenovae. Infection 30 (2002): Scott, David. The Return of Maggot Therapy. The Daily Telegraph BASF 1997 < Sherman, Ronald. Home page. January 1996 < Sherman, Ronald A., Sherman, Julie, Gilead, Leon, Lipo, Mordechai, Mumcuoglu, Kosta Y. Maggot débridement therapy in outpatients. Archives of Physical Medicine and Rehabilitation 82 (2001):