Autumn Newsletter 2007

Well, Spring and Summer have been and gone and still no rain (in case you haven't noticed). Hopefully it remains true to say it has to be closer than it was.

It has been a long and difficult breeding season because of the drought but most of the mares have gone in foal. Now to keep them that way! The caterpillars are back and worse than ever, so please keep your mares away from them. Visit our website of www.equivetaustralia.com for control methods.

Robyn has finally started to empty some yards at the EBC and we are looking forward to some time off. I think we have managed to get out of going to the UK. Eric will still go and we will follow only if necessary.

Finally our congratulations to our new vet Louise Cosgrove who has recently married Jason Gray. We wish them all the best for the future. Louise will continue to practice under her professional name of Louise Cosgrove.

Until next time

Max

The Use of Honey in Veterinary Wound Management

Honey has been used as medicine for thousands of years, in both human and veterinary practice. Much of its popularity stems from the fact that honey is a broad-spectrum antimicrobial agent. In addition, honey has many other properties that contribute to its effectiveness as a wound dressing. Although honey therapy is often considered to be 'folk' or 'alternative' medicine, scientists and clinicians around the world are gathering increasing amounts of evidence for its clinical use. This article outlines the antimicrobial and wound healing properties of honey, and also addresses some practical issues relating to its clinical use.

The antimicrobial properties of honey

It is very important to keep in mind that honey is not a generic product, as it is commonly viewed. From a culinary point of view, honeys vary greatly in taste and colour depending on the type of flowers the bees visited to collect nectar. Importantly, from a medical point of view, the antimicrobial activity of honey also varies greatly depending on its floral source. Several factors contribute to the antimicrobial activity of honey. Firstly, its high osmolarity and low pH prevent the growth of most microbial species. Secondly, honey contains a bee-derived enzyme, glucose oxidase, which produces hydrogen peroxide when the honey is diluted. Because this production occurs continuously and at low levels, it is sufficient to act as an effective antimicrobial agent without harming surrounding patient tissues. Phytochemicals derived from the floral source of the honey can also augment its antimicrobial activity. Honeys from certain Leptospermum species in Australia and New Zealand exhibit high activity due to photochemical factors, making them particularly effective for preventing and treating infections (11).

Honey has been shown to inhibit the growth of most common pathogens in vitro (11), including Staphylococcus aureus (5), Pseudomonas aeruginosa (4), Candida albicans (8), and other fungi (3). Antibiotic resistant strains of these organisms are equally sensitive to honey (6), making it an effective treatment where conventional approaches may be of reduced benefit. Clinical studies have shown that honey prevents and eradicates infection (10), negating the need for topical or systemic antibiotics. In addition, the glucose in honey provides a preferable energy source for protein-degrading bacteria, resulting in rapid deodorization of wounds (12). However it is important to note that not all honeys are the same in terms of therapeutic activity. Many honeys have no activity beyond the osmotic effect, while some may be many times more active than others (1). Therefore it is critical to use honey that has been specially selected for high antimicrobial activity if it is destined for therapeutic use.

Honey as a wound healing agent In addition to its antimicrobial activity, honey also stimulates wound healing, regardless of the infection status of the wound. When honey is placed on a wound it creates a moist environment conducive to rapid healing. Its osmotic action draws debris and necrotic tissue out of the wound bed, negating the need for surgical debridement and allowing contaminants to be lifted off with the dressing. It also draws fluid through the wound bed, contributing to the rapid development of healthy granulation tissue and re-epithelialisation (13). The honey forms a viscous layer between the wound and the dressing, allowing for painless dressing changes without disturbing the newly grown tissue. Several clinical observations show reduced inflammation and oedema in wounds treated with honey (13), and histological examination shows a reduced influx of neutrophils and other inflammatory cells (14). This also correlates to a reduction in pain. Honey stimulates angiogenesis (7, 9), and collagen synthesis (15, 16), and epithelialisation (2). It has also been shown to modulate inflammatory cytokine release in vitro (17). This may explain the effectiveness of honey in the treatment of chronic or non-healing wounds, as it can 'kick-start' the immune system.

Practical considerations Honey may be used to dress a variety of external wounds including bite and scratch wounds, degloving injuries, burns, ulcers and other chronic or non-healing wounds, as well as dermatological disorders. Other types of injuries such as abscesses may also be treated with honey, provided there is some opening to the surface to allow the honey into the site and exudates to drain. As honey is a broad spectrum antimicrobial it is unnecessary to use concurrent antibiotic therapy, making it an economical and effective dressing, particularly for large wounds.

The fluidity and stickiness of honey can be a practical challenge in dressing wounds, particularly as it becomes diluted by wound exudates. The best practice is to spread honey on the wound (deep wounds can be packed with honey) and cover with a protective absorbent dressing, or spread honey on the dressing before placing it on the wound. A secondary occlusive or non-absorbent dressing may also be necessary to prevent leakage. Use a dressing that will hold sufficient honey in place, ensure that the whole wound is in full contact with the honey and that the dressing is not so absorbent that it draws the honey away from the wound. The frequency of dressing changes depends on the wound and its level of exudates. Dressings may need to be changed daily at first. However, as the wound begins to heal dressing changes will become less frequent due to the anti-inflammatory and antimicrobial properties of the honey. If the dressing pad sticks to the wound when it is being removed, the dressing needs to be changed more frequently and/or more honey needs to be used. Any residual honey can be rinsed off easily with water.

The two most common mistakes made in the clinical application of honey are not to use enough honey, or too use the wrong type of honey. Any honey used as a wound dressing should be selected for optimal antimicrobial activity. Also, unprocessed honey may contain bacterial spores, which theoretically could germinate if introduced to the wound environment (although this ahs never been recorded throughout the long history of the clinical use of honey, in both veterinary and human medicine). Although some untested and unprocessed honeys may give good results, there are ethical issues to be considered with regards to a possible contamination of the wound with bacterial spores, and the level of antimicrobial activity not being guaranteed. Medicinal honey products available in Australia include the Medihoney brand (www.medihoney.com.au), which produces sterilized honey in a tube, a wound gel and an eczema cream. These are available from pharmacies and some supermarkets. Comvita, a New Zealand brand, also produces sterilized honey, as well as honey-impregnated alginate dressings (ApiNate). These products are available online (www.comvita.com) or in health shops and pharmacies.

Julie Irish and Shona Blair
School of Molecular and Microbial Biosciences
Building G08, University of Sydney, NSW, 2006