Saturday, October 9, 2010

insects in medicine


Insects and the substances extracted from them have been used as medicinal resources by human cultures all over the world. Besides medicine, these organisms have also played mystical and magical roles in the treatment of several illnesses in a range of cultures. Science has already proven the existence of immunological, analgesic, antibacterial, diuretic, anesthetic, and antirheumatic properties in the bodies of insects. Several authors have surveyed the therapeutic potential of insects, either recording traditional medical practices or employing insects and their products at the laboratory and/or clinical level. Thus, insects seem to constitute an almost inexhaustible source for pharmacological research. Chemical studies are needed to discover which biologically active compounds are actually present within insect bodies. The therapeutic potential of insects represents a significant contribution to the debate on biodiversity conservation, as well as opening perspectives for the economic and cultural valorization of animals traditionally regarded as useless. Their use needs to be at a sustainable level to avoid overexploitation insects.

Insects and insect-derived products have been widely used in folk healing in many parts of the world since ancient times. Promising treatments have at least preliminarily been studied experimentally. Maggots and honey have been used to heal chronic and post-surgical wounds and have been shown to be comparable to conventional dressings in numerous settings. Honey has also been applied to treat burns. Honey has been combined with beeswax in the care of several dermatologic disorders, including psoriasis, atopic dermatitis, tinea, pityriasis versicolor, and diaper dermatitis. Royal jelly has been used to treat postmenopausal symptoms. Bee and ant venom have reduced the number of swollen joints in patients with rheumatoid arthritis. Propolis, a hive sealant made by bees, has been utilized to cure aphthous stomatitis. Cantharidin, a derivative of the bodies of blister beetles, has been applied to treat warts and molluscum contagiosum. Combining insects with conventional treatments may provide further benefit.
Introduction: Why Insects?
Insects and other arthropods provide ingredients that have been a staple of traditional medicine for centuries in parts of East Asia, Africa, and South America. While many of these ingredients have not been evaluated experimentally, an increasing number have been shown in preliminary trials to have beneficial properties. Although medical practitioners in more economically robust countries may prefer conventional treatments, it may be more a result of squeamishness rather than science. Furthermore, in parts of the world where conventional medical care is scarcer than arthropods used by folk healers, insects may represent a feasible substitute in some cases. In sub-Saharan Africa alone, the World Health Organization estimates that $20 billion will be needed to replace the shortage of 800,000 conventional health care workers by 2015. (1) Globally ubiquitous, arthropods potentially provide a cheap, plentiful supply of healing substances in an economically challenged world.
The most well-studied medical application of arthropods is the use of maggots--the larvae of flies (most frequently that of Lucilia sericata, a blowfly) that feed on necrotic tissue .(2) Traditional healers from many parts of the world including Asia, South America, and Australia have used "larval therapy," (3) and records of physician use of maggots to heal wounds have existed since the Middle Ages. (3) Figure 1 depicts maggots on a wound.
Fly larvae aid in wound healing via a number of mechanisms: (1) larval secretions break the larger adhesion molecules, fibronectin and collagen, into smaller fragments that promote fibroblast aggregation and tissue repair; (4) (2) larvae eat necrotic tissue that would otherwise form a nidus for infection, liquefying such tissue and aiding its digestion; (4) (3) maggots release antibacterial substances, some of which are produced by Proteus mirabilis bacteria that live naturally in the larval intestine; and (4) ingested bacteria are destroyed within maggots. (3)
Maggots commercially grown under sterile conditions are used in wound healing. In one application technique, a hole is cut in a hydrocolloid dressing over a wound. (3) The maggots are lifted out of a container on a piece of nylon netting, which is folded together and taped onto the dressing over the hole after removal of the moisture in the maggot growth medium. A piece of gauze is placed over the nylon and taped in place. (3)
In one study, maggots were grown in vitro and placed in the wounds of 30 individuals after bacterial swabs of the wounds were taken. (5) The patients had arterial or venous stasis ulcers, diabetic or pressure ulcers, or chronic postoperative wounds. Secretions taken either from maggots grown on sterile plates or from wound sites sampled from 1-5 days after the introduction of larvae were studied for antibacterial properties. Larval secretions successfully suppressed Staphylococcus aureus growth in vitro. In vivo, 51 wounds (83.2%) healed, with reduced bacterial counts within the wounds.
Maggots were also used to treat chronic leg wounds in several patient series. In one case series involving 34 leg wounds of at least three months duration in subjects ages 32-84, 85 percent of the wounds healed. (6) Of the healed wounds, 93 percent resolved within 7-10 days. In a second series, 70 patients, ages 25-94 with wounds of at least six weeks duration, were given treatment with one-day-old larvae added at a concentration of 5-10 larvae/[cm.sup.2]. (2) Eighty-six percent of the subjects had a 66- to 100-percent reduction of wound size. During treatment, 35 percent of subjects perceived more pain, 25 percent less pain, and 46 percent no difference in pain. In a third case series, larval therapy was applied to 70 chronic wounds; 43 percent of the wounds were completely debrided, and 29 percent were partially debrided. (7) There are also case reports of the successful use of maggots for treating the wound of a terminally ill patient (8) and for non-healing venous ulcers. (9)
One study examined the factors that predict better outcomes of larval therapy in a series of 117 wounds. Greater wound depth, older patient age, and presence of septic arthritis portended a worse outcome. (10)
Larval therapy has also been evaluated in controlled trials. In a randomized trial, 267 subjects with venous or arterial ulcers at least 25-percent covered with necrotic material were assigned to receive maggots or a conventional hydrogel dressing. (11) Although there was no difference in rate or timing of healing between groups, the maggot-treated wounds were debrided significantly faster (2.31 days; p< 0.001). On the other hand, subjects treated with maggots had a significantly higher pain score (approximately 40 points higher on a 150-point analog scale; p< 0001). In another trial involving diabetic leg ulcers, non-healing wounds were treated with either maggots, a conventional hydrogel, or the conventional therapy followed by larval treatment. (12) Wounds treated with maggots had significantly less necrotic tissue after two weeks. Thus, there is limited evidence that larval therapy can provide wound healing for lower extremity ulcers comparable to conventional treatment. A systematic review concluded that, in appropriate patients, use may be safe and effective. (13) Maggots may be appropriate especially when conventional therapies cannot be used, or in parts of the world where larvae are more easily obtainable than conventional treatment.
Honey Treatment
Honey is another insect-derived substance that has been used in wound healing and for treatment of other disorders, such as infections and irritable bowel syndrome. Therapeutic effects of honey have been documented from ancient times and it is still used in African folk medicine. (14, 15) Honey composition varies widely throughout the world depending on the species of bee and plants the bees feed on, both of which influence the honey's antioxidant and antimicrobial properties. (16-18) Four phenolic compounds in honey--p-hydroxybenzoic acid, naringenin, pinocembrin, and chrysin--are antimicrobials and antioxidants. The carbohydrate in honey is also antimicrobial. (16, 17) Honey also has antimutagenic properties. (19)
Wound Healing
The best studied use of honey is for wound healing. Honey promotes wound healing through osmotic properties that serve to moisturize the wound bed and reduce the risk of maceration. It also works via anti-inflammatory processes that reduce exudate and inhibit fibrin that adheres eschar to the wound bed, impairing tissue repair. (20)
Honey has been used to heal wounds in numerous situations. Many studies have found dressings that contain honey comparable to conventional dressings. In a randomized, double-blind, placebo-controlled trial, 100 patients who had toenail surgery were assigned to receive either a honey-coated dressing or a conventional paraffin dressing. (21) There was no significant difference between groups in days taken to heal the wounds.
However, in a single-blind study (blind to the investigator who examined the wounds), honey proved inferior in healing time to a conventional iodine dressing in 57 patients who had total avulsion toenail surgery, but comparable in wound-healing time to standard treatment after partial avulsion surgery. (22)
n a case series, eight patients (ages 22-83) with leg wounds that had not healed in a month were given once- or twice-weekly applications of honey on a non-adhesive dressing. (23) After a month of treatment there was an average 54.8-percent reduction in wound size, from a baseline mean wound size of 5.62 to 2.25 [cm.sup.2]. (23)
Two open (unblinded) trials also found significant wound healing with honey.

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