For decades, laboratories in several countries, including France, the United Kingdom, the United States, Turkey and Ukraine, have been breeding medicinal leeches. Carl Peters-Bond of Biopharm UK, a company that supplies about half of the medicinal leeches used in hospitals around the world, has been working on this for almost three decades. He said it takes between one and two years to raise a leech ready to be used for medicinal purposes. The process involves feeding them at 3 weeks, then between 8 and 10 weeks, then at 4 or 5 months, after which they are starved for up to two years. “We only ship leeches on an empty stomach,” he says.
As soon as he receives an emergency call, Peters-Bond packs between ten and sixty leeches in a jar filled with gel and ships them to the hospital. Sometimes, hospital pharmacies order them in advance and store them in a refrigerator for when a patient with a severed finger, or requiring ear reattachment or breast reconstruction, needs them. These creatures, however, have a three-month expiration date.
When a leech bites, it slowly sucks blood and injects compounds found in its saliva, such as hirudin and calin, which prevent blood clotting. This saliva also contains histamine-like substances, which dilate vessels and improve blood flow. Doctors have previously used blood thinners like heparin to prevent blood clots from forming during reconstructive surgeries. Active suction of blood is still necessary, however, explains Agarwal.
Depending on the size of the grafted tissue and the degree of congestion, the suction may continue for three to 10 days, or even longer, until the tissue looks “less swollen, less purple, more normal,” Janis describes. Patients remain in the hospital and medical staff oversee the process, replacing each engorged leech with a new, hungry leech. Each critter can only be used once and is drowned in alcohol after completing its mission.
Within two weeks, more than 100 leeches drained Ms. Lofgreen’s tissue. Every four hours, a nurse would come and place a new leech, which would feed for 15 to 120 minutes before falling onto the patient’s bed. During treatment, to replace the lost blood, doctors gave him blood transfusions.
It was sometimes difficult to get the leech to hang on properly, and even harder to make sure it stayed where it was. The nurses began by using small plastic cups, which they stuck to Ms. Lofgreen’s skin to contain the animals; but that did not prevent them from escaping regularly. The staff then created a barrier using a piece of gauze with a hole where they wanted the leech to attach, hoping that the gauze would deter it from venturing onto the surrounding skin. This method was not foolproof either. The most effective technique was the attentive gaze of Mrs. Lofgreen’s mother and sister. Throughout the day, they took turns to spot the rebellious leeches and immediately alert the nurses. The patient, for her part, felt nothing when these parasites bit into the transplanted tissue, but felt a brutal pinch when they bit elsewhere. “It was like needles,” she said.
Over time, the area of tissue that initially appeared dark and necrotic became light purple again, and the skin took on a more normal appearance. “We’ve had some success with leeches,” says Ms. Lofgreen. But after returning home, a small section of the flap became infected and had to be removed. The infection was not related to leeches, but rather resulted from an open wound. She credits the slimy, slippery creatures with saving the majority of the transplanted flap.
According to a study of 277 cases of use of medicinal leeches, the success rate of this method is 78%. “It’s a very interesting option for saving flaps,” says Ernest Azzopardi, a specialist in plastic surgery at University College London in England and co-author of the study. The lack of robust randomized controlled trials, which are a benchmark for assessing the effectiveness of any intervention, has nevertheless led to a loss of confidence in the use of leeches in a medical setting.
Furthermore, following these treatments, some patients may develop skin infections due to the bacteria. Aeromonas which lives in the guts of leeches and can move through their saliva. Leech breeders like Peters-Bond don’t use antibiotics: he says drugs can kill these intestinal bacteria, but they come back. “What we do is we starve the leeches so that there is no blood in the intestine, and thus reduce the bacteria to a minimum. » In hospitals, doctors typically prescribe antibiotics to patients as a preventative measure, but evidence is beginning to indicate that some bacteria Aeromonas are developing resistance to commonly used medications, making treatment use even more difficult.
For years, scientists have been looking for alternatives to medicinal leeches. The first attempts date back to the 19e century, when the demand for leeches was very high in Europe, and the invertebrates were becoming rare, and therefore more expensive. In 1817, Jean-Baptiste Sarlandière, a French anatomist and physiologist, developed a device called a bdellometer, which allowed blood to be drained from patients.
Since 2013, Agarwal has worked with colleagues at the University of Utah to create a mechanical leech capable of delivering an anticoagulant, but also of imitating the animal’s sucking effect. The prototype consists of a network of needles that puncture the skin; a central needle would deliver the anticoagulant heparin to blood-saturated tissues, and surrounding needles, connected to a pump, would draw the blood. This device would allow doctors to control the volume and flow of blood drawn, which is not possible with real leeches. For now, the team is still trying to perfect the flow of anticoagulant into the tissues to which the device is attached.
Other scientists have also developed similar and promising prototypes. Some have tested their performance on animals, but according to Azzopardi, we are not yet at the stage where we can start using any of these mechanical alternatives on humans. For now, leeches continue to occupy a small but important place in modern medicine.
