Eye of Newt and Toe of Frog?

First published in the NASGP Newsletter on 4th September 2023

A friend’s story: when he was a teenager an eye was severely damaged by a shuttlecock. One conservative treatment after another failed. The consultant decided to try surgery. But he couldn’t see to operate for the blood. He found a way to keep the operating field clear. My friend’s eye and some sight was saved, and he asked the surgeon for a certificate on headed paper to confirm his treatment. Why? He used it to win bets with medical students who didn’t believe that leeches were still in use.

That was 1958. Therapeutic bloodletting, which had contributed to thousands of deaths, was finally abandoned at the end of the nineteenth century. But leeches still had a bad press. In 1973 when I took off my boots after a day in the jungle of Papua New Guinea, I watched fascinated and somewhat horrified as the blood trickled from several punctures. And went on trickling. I felt no pain and discovered that leeches had wriggled in through the lace holes.

Yuck warning: I’m going to talk not just about leeches, but also maggots, spiders, slugs and snails, if not puppy dog tails. Many ancient medical practices were consigned to history when 20th century technology came up with convenient, modern alternatives. But they were expensive. And they didn’t solve every problem. As my friend’s surgeon came to realise.

Can a ‘primitive’ invertebrate possibly do better than us?

Now, Hirudo medicinalis is valued for those qualities that I found disturbing: the anaesthetic and the anticoagulant they infuse to facilitate the ingestion of blood. A Welsh farm produces 60,000 leeches a year for hirudotherapy. They are reared on sheep’s blood and starved for six months, by which time they are sterile and hungry, ready to drain haematomas and keep micro-surgical operating fields clear of blood. When they have done their job they are dropped into alcohol to kill them and disposed of as biohazard waste.

The public image of maggots is even less flattering. But put them head-to-head with surgical debridement and they win hands down for precision and healing time. Maggots – fly larvae – eat only dead tissue and they consume the bacteria which otherwise delay healing and may lead to sepsis. Aboriginal tribes appreciated this, as have some medics since the Napoleonic wars. Now larval debridement therapy using medical-grade maggots is widely used in Britain. Most hospitals provide information leaflets to overcome patients’ anxieties, and if you have suffered for years with diabetic foot ulcers, maggots are a miracle.

Every year the NHS spends around £10 billion on wound care. Only care of diabetes and cancer cost more. Two or three visits a week from district nurses account for 30% of the total. An estimated 100 million prescriptions are issued for drugs and approaching 300 million for dressings. Diabetes, obesity, pressure sores and elderly patients with fragile skin – all are increasing, but the number of district nurses has fallen catastrophically.

Few GPs know much about wound dressings. They tend to leave the selection to nurses who, faced with mucky-looking, poorly healing wounds may ask for antibiotics to treat the growth on a swab and be inclined to try yet another promise-laden and expensive product.

Patients with chronic wounds are prescribed an average of eight types of dressing. When I was an Senior House Officer on an elderly long-stay ward, one of the sisters was a lone voice promoting honey therapy for wounds. Maybe she had studied ancient Egyptian medical papyri. Now, most formularies list medical grade honey. It is anti-microbial and antioxidant. Dressings incorporating honey are light. They can be left on longer than conventional dressings, and a thin layer of skin can form before they are rolled off. A saving in patient discomfort, nursing time, healing time and antibiotic use.

Natural materials can have properties which have been used for centuries before their active ingredients were identified. Ancient Greeks and Romans didn’t know about Vitamin K and antimicrobials, but they knew spider webs staunched bleeding wounds. In ‘A Midsummer Night’s Dream’, Bottom says to fairy Cobweb “If I cut my finger, I shall make bold of you”.

Now researchers are making bold of Cobweb. There are 1.5 million nerve repair operations every year and most require making another wound to harvest a nerve for an autograft. Invasive, tricky and expensive. To reconnect successfully over any distance, the two ends of the nerve need a tube to tunnel through and a structure inside to support them. Manmade structures have proved unsatisfactory. Silkworm silk can provide the tube, spider silk the support. They are minimally allergenic and they degrade. E coli cultures are used to synthesise spider silk, adding an unusual amino acid onto which molecules can be chemically ‘clicked’ to expand its functionality..

In the zoology department where I did my first degree one researcher worked on slime, another on resilin, the super-elastic that enables fleas to jump so effectively. At a time when John Gurdon in the lab next door was implanting nuclei from mature skin cells into enucleated eggs which then grew into tadpoles, work that earned him a Nobel prize, these were niche interests.

The time has come for slime. The mucus we produce in our noses, lungs and gut is part of our defence against infection. Slug and snail slime has a yuk factor, but the ancients made use of its viscosity and antimicrobial powers. As a glue it was invaluable for mending wounds because it’s not toxic, it sticks under water and doesn’t dry out. It could be again.

Resilin might turn out to be a miracle repair too. To our forebears, fleas were a nuisance and carriers of disease. They could see no use for them except in flea circuses. But resilin beats any man-made elastic. Spinal discs wear out like knicker elastic. Because fleas must jump thousands of times during their life, resilin doesn’t wear out.

As homo sapiens we are inclined to look down on our fellow-creatures. Can a ‘primitive’ invertebrate possibly do better than us? The answer is, yes, it can if we overcome our prejudices and revulsions. Ancient texts and research driven by open-minded curiosity can change medical practice.

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