Leeches are segmented worms that typically live in wet environments, such as streams, ponds, or rivers. They attach themselves to the skin of mammals, including humans, in order to feed off their blood.
Historically, leeches were used in bloodletting, a therapy that came out of a medical philosophy developed by the ancient Greek doctors Hippocrates and Galen known as Humourism. It imagined that the body was composed of four ‘humours’ – blood, black bile, yellow bile, and phlegm; keeping these balanced kept a person healthy. The idea behind bloodletting, or more specifically ‘leeching’, was to get rid of excess or ‘bad’ blood in order to recover from illness more quickly.
Bloodletting dominated Western medicine for 2,000 years and associated treatments – including leeching – began to decline in the late 19th century. It was at this point Germ Theory began to be more widely accepted in society and diseases were shown to be the result of microbes rather than humours.
But leeches are making a comeback in hospital medicine – just not as a way to balance the humours! In a process called Leech Therapy or Hirudotherapy, they have been found to be excellent helpers in stimulating blood flow and removing the build-up of coagulated or excess blood. This is key in the reattachment of limbs and in plastic surgery when tissue needs to be grafted from one part of the body to another because increased blood flow encourages faster healing and reduces the likelihood of necrosis – or death – of the tissue.
Moreover, the anaesthetic properties present in the saliva of the leech also offers a relatively painless way to encourage healing. Nowadays the most commonly used leech is the Hirudo medicinalis, or ‘medical leech’, and it is farmed in sterilised conditions to keep patients safe.
Perhaps one of the more unexpected characters on this list is the Lucilia sericata, otherwise known as the common green bottle fly. While typically considered a pest and nuisance, inspiring numerous designs for fly traps and swatters, the bottle fly has been a friend to the injured for many centuries.
While we tend to think of flies purely as disease vectors or carriers, when reared in a carefully sterilised laboratory environment, fly larvae –maggots – can be used to treat wounds. They eat diseased and dead skin, and will clean the wound as they do which speeds up healing times. Maggot Therapy is particularly helpful in wounds that have antibiotic resistant infections: maggots keep the area clear of all the infected tissue regardless of the type of bacteria present.
Outside of their direct medical use, flies and their larvae have also been used in a variety of scientific contexts. One example is how they, with other insects, are used in forensic entomology to determine times of death as well as environmental factors in a crime. Additionally, fruit flies have played a major role in biomedical laboratory research. They are often used as models in experiments and play a significant role in the development of studies in gene expression, gene regulation and mechanics, and mutations.
The importance of bees as pollinators is well known and protecting them has become imperative with the increase of urbanisation and deforestation in our modern world. Their incredible contribution to our society doesn’t stop at their role in our ecosystem, however. For thousands of years bees have produced materials which have been crucial to everyday lives – from beeswax candles which give us light, to honey used to sweeten food. And yes, bees and their products continue to be used in medical contexts today!
Beeswax is a waxy substance bees create from sugars using a gland on their abdomen; they use it to build their hives and store food. It has a high melting point relative to other waxes and can be moulded easily into a variety of shapes so it is ideal for candles and decorative art and sculpture. These same properties also have applications in the medical world, for example making casts of teeth in dentistry and use as a protective skin barrier, such as breastfeeding nipple guards.
Beeswax is also an excellent emollient and humectant: applying it directly to the skin can hydrate, soothe, and soften. Beeswax has long been added to cosmetics and pharmaceutical lotions and creams for this purpose. It continues to be used in many products to help with conditions such as eczema or psoriasis.
However, it’s not just beeswax that we have used for medical purposes. Honey has played a significant role in human history for at least 8,000 years. While not all bees make honey, it is perhaps one of the most well-known substances associated with bees – and certainly one of the most sweet and delicious! Honey has played a significant role in the history of medicine too. It is a natural antimicrobial agent and antibiotic, meaning it slows and sometimes stops the spread of bacteria and other potentially harmful germs in our bodies. Its antibiotic uses have been documented since ancient times and it is still often taken to treat internal infections ranging from stomach ache to sore throats.
Today, honey impregnated bandages are available on the NHS – using medical grade sterilized honey, rather than table honey! – and these are used to treat surgical wounds, burns, and ulcers to name but a few. The antibacterial nature of honey alongside its natural ability to keep skin soft and moist while offering a protective barrier, means it is excellent for encouraging skin to heal.
Even if they bug you, insects are amazing creatures which help us in surprising ways. In modern medicine, these critters and their products encourage us to heal and offer powerful protection from infection. Throughout history, they have been an important part of science and medicine – perhaps the best way we can thank insects is to create rich and diverse ecosystems to stop the serious decline in insect biodiversity that the planet is currently facing.