The Role of Pests in Medicine

Ehrlich Pest Control

Have you ever heard the gardening expression, “a weed is just a plant in the wrong place?” We believe that pest infestations should be prevented or controlled, but essentially, a pest is just an animal in the wrong place. Animals like leeches, maggots or parasitic nematodes have very important roles to play in the environment. What you might not expect, though, is that they may have important roles to play in treating our ailments today.


Perhaps the most famous of the pre-scientific ‘gross’ treatments was leeches. By the mid-1800s, the demand for leeches in Europe was so large that a German exporter shipped over 30 million leeches a year. Leeches were applied to patients to treat everything from headaches and haemorrhoids to unbalanced humours. They believed that the human body was made of four ‘humours’ (blood, phlegm, yellow bile and black bile) and when they were unbalanced, it resulted in illness. The normal treatment was blood-letting, the attempt to put the humours back in balance by taking blood out of the body.

These days, leeches are used with a much better idea of what makes us ill, and how leeches can help us heal. The saliva leeches excrete can lessen pain, prevent blood clots and reduce swelling. Patients who have had reconstructive surgery in areas that have lots of small blood vessels, like the face or ears, benefit from these qualities. The small blood vessels can clot easily, leading to swelling, and in the worst cases, cells dying from a lack of oxygen and other nutrients. Applying leeches to the area can keep the blood from clotting and help the cells from essentially drowning in blood.

Aside from medically approved treatments, some people insist leech therapy can be used to maintain a younger appearance. Demi Moore admitted in 2008 to having a beauty treatment which, much like mediaeval blood letting, involved having leeches suck her blood to ‘detoxify’ it.


Maggots which are flies in their larval stage have been used to treat wounds for millenia. The Old Testament in the Bible documents the treatment of wounds with maggots. Early civilizations noticed wounds infected with maggots would heal better than those that were not infested. One of the first officially documented medical application of maggots to a wound was recorded by Dr John Forney Zacharias, an American civil war surgeon. He noted that maggots would not eat live tissue, instead cleaning the dead tissue out of a wound faster and more thoroughly than humans could. He asserted that his use of maggots saved lives, helping patients avoid septicaemia and recover more quickly.

Despite the well-known effectiveness of applying maggots to gaping wounds, doctors had little understanding of how maggots were able to not only clean wounds, but make seemingly mortal injuries heal quickly. Now we know that in addition to eating dead tissue (called debridement), maggots also disinfect wounds and stimulate the healing process. The maggots’ secrections act as powerful anti-microbials and somehow stimulate the growth of skin.

Maggots do require a specific environment to do their jobs, though. A wound must be moist, have a good supply of oxygen and not be in the body cavity. Once they are applied, dressings have to be designed to allow oxygen in, keep the maggots in and reduce the tickling sensation patients sometimes feel. Moreover, one study has indicated that maggots are roughly as effective and affordable as a standard hydrogel when treating leg ulcers and that patients reported feeling more pain with the maggot treatment.


The theory behind the medical use of nematodes is based on the hygiene hypothesis: the theory that humans developed alongside various parasites and bugs, and because people in developed nations have removed themselves from unsanitary conditions, allergies and autoimmune disorders have increased as people’s immune systems have grown weaker.

There are, of course, other factors – mostly genetics – which obviously are more directly responsible for non-viral autoimmune disorders, but some research has indicated that a genetic predisposition towards diseases like Crohn’s, combined with the lack of parasites, and especially intestinal nematodes, can account for the increasing numbers of people with autoimmune disorders.

So proponents of helminthic therapy suggest innoculating patients with the microscopic nematodes to strengthen the immune system.  Though its effectiveness has not yet been thoroughly proven, helminthic therapy seems promising, and scientists are studying it in laboratories in England, the United States, Australia and Argentina.

Parasitic nematodes are a severe threat to the health of people living in less developed countries, leading to diarrhoea, weight loss and anemia.

But as gross as blood sucking and flesh eating bugs are, when they have healed wounds and prevented amputations they start to look less like pests and more like animals in the right place.

Picture Credits
Leeches Image by Fitch & Nottingham, London on Wikimedia Commons

Image by Karl Ragnar Gjertsen on Wikimedia Commons

Maggots Image by Shakey Dawson on Wikimedia Commons

Nematodes Image  Image by Jasper Lawrence on Wikimedia Commons 

Ehrlich Pest Control
Ehrlich Pest Control

Since our founding in 1928, Ehrlich Pest Control has grown to over 100 local offices serving both residential and commercial customers throughout the Eastern U.S. Long lasting relationships with colleagues and customers is a cornerstone of our success. Many Ehrlich colleagues have been with the company for 25, 30 and 40-plus years.

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