Watching a medicinal leech swelling as it sucks blood from a recently sutured abrasion isn’t for the squeamish. Think of maggots, leeches, roundworms, ants and spiders – if you can bear to – and you see them as pests or parasites. But hospitals and medical researchers are finding new applications for creepy crawlies.
‘Leech: An aquatic or terrestrial annelid worm with suckers at both ends. Many species are bloodsucking parasites, especially of vertebrates, and others are predators ... a person who extorts profit from or sponges on others’. So says the Oxford English Dictionary. It’s fair to say that the leech doesn’t have a great media profile. But the dictionary offers a second, more positive definition: ‘(archaic) a doctor or healer’. All the way back to Hippocrates, the medicinal leech (Hirudo medicinalis) has played its part in medicine and pharmacology, and in the 21st Century they – and other creatures more commonly thought of as parasites or pests – are making a medical comeback.
Not many years ago, a visitor to Istanbul’s famous bazaar, the Misir Carsisi, might see vendors selling jars of wriggling medicinal leeches, used to ease all manner of ailments. No longer. Medicine in Turkey has moved on into an era of high-tech hospitals and 21st Century treatments and procedures that can be billed to private health insurance providers. Traditional, do-it-yourself remedies like the leech are a thing of the past.
Ironically, just as Turkey has abandoned such age-old treatments, medical science is rediscovering them. Hospitals in Europe and the US are increasingly interested in the potential benefits of the humble leech as an aid to post-surgery recovery. In the UK and more and more frequently in other countries, leeches are used in microsurgery, where they have been shown to be useful in the prevention of post-transplant necrosis. Natural anticoagulants that they inject at the site of their bite have been found to increase blood flow to newly transplanted body parts.
“Even as late as 1896, some hospitals were still ordering stocks of leeches, and they continued to be used in some parts until the Second World War,” said Dr Alun Withey, an academic historian of medicine at the University of Exeter, UK. “After centuries of emphasis upon medical progress, and the ignorance of patients and practitioners in the past, it is interesting to see the ways in which past practices and beliefs are again beginning to find their way into orthodox medicine.”
Meanwhile, in the UK and the US, surgical staff are using leeches, which have been cleared for use as ‘medical devices’ since 2004 by the US Food and Drug Administration, to drain blood from sutured wounds and simultaneously prevent further clotting, allowing faster healing after plastic surgery. A thoroughbred medicinal leech from Biopharm Leeches, which supplies UK National Health Service medical establishments such as the Royal London Hospital costs £12. Biopharm also sells its wares in the US, Italy, Scandinavia, China, Japan, Korea and South Africa. The South Wales-based company has been in the bloodsucker business since 1812. “Biopharm is the first leech farm of its kind and we are innovators in the cultivation of the medicinal leech, currently producing the majority of leeches used in modern medicine worldwide,” said Biopharm’s Carl Peters-Bond. The potential of leeches in post-surgical treatment began to be recognised with the astonishing advances in micro-attachment surgery over the last 30-50 years, he said. “We were among the first to recognise that potential.”
Biopharm, based in Swansea, Wales, has nurtured the renaissance of leeches in modern plastic and reconstructive surgery worldwide, rearing and selling up to 50,000 medicinal leeches a year. Around 20,000 of those go to hospitals in the UK. The rest are exported to Biopharm’s network of partners worldwide. At £12 per leech, and considering that leeches live in any old pond, that sounds like easy money.
However, it’s not as easy as getting out there with a net and a bucket. Raising medicinal leeches is ‘quite a long and difficult process’, said Peters-Bond. “They need to be kept in a sterile environment while growing. We feed them three times over about a year; when we despatch them they are between three and four years old. It’s quite a difficult and lengthy process, and exporting them internationally involves lots and lots and lots of red tape.”
Cut-price Russian bloodsuckers
For Biopharm, that could be a blessing in disguise. In Russia, leech treatment remained in common use in the Soviet era and is still popular. Hospitals and clinics still use around 10 million leeches each year, as they did in Soviet times, to relieve conditions ranging from back pain, liver disease and high blood pressure to glaucoma, though their efficacy in treating such ailments is questionable. More recently, Russian medicine has seen leech therapy’s main benefits as deriving from the natural anti-clotting agents found in leech venom used in the prevention of cardiac conditions and stroke, and delivered directly by live leeches much more cheaply than pharmaceutical anti-coagulants. The International Medical Leech Centre in Moscow sells its leeches for less than £1 each (minimum order 10,000, cash up front) but bureaucratic obstacles have so far prevented it from breaking through into UK and European Union (EU) markets, so these are unlikely to be flooded with cut-price Russian bloodsuckers any time soon.
After centuries of emphasis upon medical progress, and the ignorance of patients and practitioners in the past, it is interesting to see the ways in which past practices and beliefs are again beginning to find their way into orthodox medicine
Like treatment using leeches, maggot debridement therapy (MDT) was well known historically. Some military surgeons reportedly noted that maggot-infested wounds healed more quickly, with a lower mortality rate. In the 1920s, an American surgeon working at Johns Hopkins Hospital in Baltimore, William Baer, conducted research into MDT with hopeful results, and the technique was widely used until the 1940s. It fell from favour with the advent of antibiotics, but is being re-examined as hospitals seek alternative forms of treatment. “The first modern clinical studies of MDT were initiated in 1989 at the (US) Veterans Affairs Medical Center in Long Beach and at the University of California,” according to Dr Ronald Sherman, a founder and board chairman of California-based non-profit organisation the BTER Foundation, which aims to improve access to maggot and leech treatment and other biotherapies. “By 1995, a handful of doctors in four countries were using MDT. Today, over 3,000 therapists are using maggot therapy in 20 countries.” Sherman, who began treating patients using MDT in 1990, claims ‘miraculous results’ from the treatment in healing stubborn wounds.
Precise and selective
The US Food and Drug Administration and the UK’s NHS both authorised the use of maggots as ‘medical devices’ in 2004. In UK hospitals, NHS surgeons working in fields such as podiatry say MDT is cheap and cost-effective. It is also more selective than conventional debridement surgery, which involves cutting away dead flesh, but can also involve cutting away healthy tissue to ensure removal of the whole infected area. Fly larvae, however, eat away only dead tissue, so debridement is precise, and treatment does not require patients to stay in hospital to recover from surgery. Some proponents of MDT say they have observed that maggots not only remove dead and infected tissue but also help to disinfect the wound and speed healing by exuding natural antibiotic substances.
However, peer-reviewed research carried out in 2009 at three UK universities and published in the British Medical Journal indicated that while maggots are indeed better at debridement, there was no significant difference in healing time compared with treatment using hydrogel dressings. Patients in the groups using larvae also reported more pain than those in the hydrogel groups.
Hospitals in Europe and the US are increasingly interested in the potential benefits of the humble leech as an aid to post-surgery recovery
The research, which was carried out at the University of York, University of Warwick, University of Leeds and Coventry-based Micropathology Ltd and funded by the UK National Institute for Health’s Research Technology Assessment Programme, was based on a controlled study of 267 leg ulcer patients and provides the strongest evidence to date about the effects on larval therapy on leg ulcer healing, according to the NHS. “Future treatment decisions should be fully informed by the finding that there is no impact on healing time,” the researchers said, adding that further study was needed.
It sounds like something straight out of Marvel Comics, but scientists at the University of Nottingham’s SpiderLab, in the UK, have developed a recombinant (artificial) spider silk that can be used to create a biodegradable mesh that can be used to accelerate growth of new tissue and for the slow release of antibiotics. “There is the possibility of using the silk in advanced dressings for the treatment of slow-healing wounds such as diabetic ulcers,” said Professor Neil Thomas of Nottingham’s faculty of chemistry. “Using our technique, infection could be prevented over weeks or months by the controlled release of antibiotics. At the same time, tissue regeneration is accelerated by silk fibres functioning as a temporary scaffold before being biodegraded.”
Dr Sara Goodacre, Associate Professor at the University’s Faculty of Life Sciences, says the work is likely to lead to ‘a very exciting range of studies’. “Some of the future work will be supported by other, neat ideas from the world of spiders and their silk, which the SpiderLab is currently trying to unravel,” she said.
Meanwhile, a group of scientists in Rio de Janeiro, Brazil, inspired by an ancient Sanskrit medical text, have developed plans for a surgical clamp based on the jaws of a large South American ant species. The use of ant mandibles to close wounds is described in the Charaka Samhita, written in India almost 2,000 years ago and the Brazilian team’s research suggests natural biopolymers such as fibroin and chitosan could be used to build absorbable clamps that mimic the action of ant mandibles. There seems to be no end to the new applications that medicine can find for ancient biomedical techniques.