Leeches

Scientific Name(s): Hirudo medicinalis L. Phylum Annelida
Common Name(s): Fresh water leech, Medicinal leech

Medically reviewed by Drugs.com. Last updated on Sep 12, 2024.

Clinical Overview

Use

Leeches have traditionally been used for bloodletting. Leech therapy has been investigated for its analgesic and wound healing effects, and for stimulating blood flow at postsurgical sites. Use in osteoarthritis has also been investigated. However, clinical trial data are lacking to recommend use for any indication.

Dosing

Consult existing institutional guidelines for recommendations regarding the use of leeches.

Contraindications

Arterial insufficiency, previous exposure to leeches (risk of allergic reaction), immunosuppression (risk of infection), patient refusal to accept possible subsequent blood transfusions, and unstable medical conditions have been described as contraindications for extensive leech therapy.

Pregnancy/Lactation

Information regarding safety in pregnancy and lactation is lacking. Avoid use because of risk of infection and anemia.

Interactions

None well documented.

Adverse Reactions

Extensive blood loss may occur. Allergic reactions and infections may develop.

Toxicology

No data.

Scientific Family

• Hirudinidae

Biology

There are more than 700 species of leeches, all of which are carnivorous.(Whitaker 2005) The leech is an hermaphrodite, containing both male and female sexual organs, but is not self-fertile.

The use of medicinal leeches (H. medicinalis) is preferred because of their ability to bite deeply and cause prolonged bleeding, even after detachment. H. medicinalis can reach up to 12 cm in length but is generally smaller, weighing 1 to 1.5 g before feeding. H. medicinalis has both anterior and posterior suckers, with the head located at the narrow, tapered end. The anterior sucker has 3 jaws, each with 60 to 100 teeth for biting. The posterior sucker is used for attachment and crawling.(Whitaker 2005)

Leeches obtained from commercial breeders are easily maintained in a chlorine-free salt solution at 10 to 20°C (50 to 68°F). Under such conditions, leeches can survive for up to 18 months.

History

The medicinal use of leeches dates back to ancient Egypt around 1300 BC. The Greek physician Galen (AD 130 to 201) commonly used leeches for bloodletting. The 19th century heralded the widespread use of leeches for bloodletting—leading to a leech shortage from 1825 to 1850 in France and requiring the importation of leeches from America.(Hayden 1988, Hodgson 2003, Rao 2003, Ventura 2005, Whitaker 2004, Whitaker 2005) By the end of the 19th century, medicinal use of leeches had lost popularity due to adoption of modern concepts of pathology and microbiology.(Whitaker 2005) Extracts from leeches have been marketed in creams for topical application.(Shakouri 2018)

Chemistry

Different species of leeches secrete varying compounds with differing hematological actions.(Ledizet 2005, Rivière 2004)

Following attachment, H. medicinalis secretes hirudin, a selective thrombin inhibitor, which enhances bleeding and prevents coagulation.(Chepeha 2002, Dippenaar 2006, Whitaker 2005) Hirudin was first described more than a century ago and characterized as a 65-amino acid peptide with antithrombokinase activity.(Whitaker 2005) Early therapeutic studies of hirudin were limited by low natural yield, but the compound has recently been produced in larger quantities by recombinant gene techniques.(Hand 1994, Wallis 1988) Recombinant hirudin binds avidly to thrombin, thus low doses inhibit venous thrombosis in animals. In addition to hirudin, leeches secrete hirustasin, which selectively inhibits tissue kallikreins; antistasin and ghilanten, which inhibit factor Xa; calin, apyrase, and saratin, which inhibit platelet aggregation; a histamine-like compound, which causes vasodilation; hyaluronidase and collagenase, which increase permeability; and bdellin and eglin, which are proteinase inhibitors.(Deckmyn 1995, Dippenaar 2006, Harsfalvi 1995, Whitaker 2005)

There is conflicting evidence as to whether an anesthetic is secreted by H. medicinalis.(Baskova 1992, Rados 2004, Whitaker 2004) Angiotensin-converting enzyme (ACE)−like properties have been detected in the Theromyzon tessulatum leech via an identified soluble enzyme named T. tessulatum ACE (TtACE).(Rivière 2004) Peptides with antimicrobial properties have also been identified.(Salzet 2005)

Undefined anti-inflammatory substances in the saliva of medicinal leeches have been reported.(Lauche 2014, Porshinsky 2011)

Uses and Pharmacology

Analgesic effects

Clinical data

In an open-label, randomized, controlled trial in patients with chronic low back pain (N=44), a single application of leeches to the lower back provided significantly greater pain relief by day 28 than a 60-minute session of exercise therapy each week for 4 weeks (P=0.0018). Global improvement, functional scores, and physical quality of life were also significantly improved in the leech group compared with the exercise group. Adverse events related to leech therapy included prolonged continuation of bleeding up to 24 hours (n=3) and more intense itching (n=2), whereas increased back pain was reported in 5 patients in the exercise group and 1 in the leech group.(Hohmann 2018) Beneficial use of leech therapy in a case of complex regional pain syndrome has also been reported in a 54-year-old male with 2 fractured fingers of his right hand.(Kulbida 2019)

In another study, either hirudotherapy or platelet-rich plasma injections at trigger points was added to standard stretching exercise treatment for patients with myofascial pain syndrome (N=66). Both treatments were effective regarding pain decreases and increased pain threshold, although clinical efficacy of medicinal leech therapy was greater.(Ediz 2021)

Improvement in pain scores has also been reported in randomized controlled trials and meta-analyses conducted in patients with osteoarthritis (see Osteoarthritis section).(Isik 2017, Lauche 2014, Wang 2018)

Blood sampling in zoo animals

Animal data

Medicinal leeches have been shown to be a viable tool for noninvasive blood sampling in zoo animals.(Kvapil 2021)

Ischemic tissue

Animal data

Medicinal leeches used to stimulate the flow of blood at postoperative surgical sites(Baskova 1992, Hayden 1988, Rados 2004) has been demonstrated in rats and pigs.(Baskova 1992, Hayden 1988, Rados 2004) Therapeutic effects related to use of hirudin in treating ischemic skin flaps were documented in a review and included an increase in surviving tissue area, improved microcirculation, reduced tissue inflammation, promotion of blood vessel regeneration, and recanalization of ischemic flaps.(Junren 2021) In a rat model, leech therapy significantly improved motility and the number of normal sperm cells as well as testicular injuries due to ischemia and reperfusion subsequent to testicular torsion/detorsion surgery.(Davoodi 2021)

Clinical data

After attaching to the site, leeches secrete compounds, especially hirudin, that reduce blood viscosity. They provide the drainage needed to permit decongestion and to preserve tissue viability until normal venous flow is established.(Abrutyn 1988)

Reviews of the use of hirudotherapy in localized venous congestion or hematoma have been published; mostly case reports exist in the literature.(Elyassi 2013, O'Dempsey 2012, Porshinsky 2011) One case included the successful use of leech therapy for 6 months on the foot of an atherosclerotic patient with a significant history of cigarette smoking who presented with critical pedal digit occlusive disease refractory to multiple other treatment modalities.(Afify 2021) In another case of ischemic priapism in a 26-year-old male with a severely painful 80-hour erection, pain and perineal swelling improved substantially 2 days after leech therapy and resolved over the next month.(Asgari 2017)

Osteoarthritis

Clinical data

Based on reported anti-inflammatory substances in the saliva of medicinal leeches, a number of clinical studies have evaluated the role of leeches in osteoarthritis.(Lauche 2014, Porshinsky 2011) Blinding of participants is problematic in such studies, and comparators have included transcutaneous electrical nerve stimulation (TENS)(Stange 2012) and topical diclofenac.(Michalsen 2003) In one randomized, single-blind study that enrolled 105 patients with symptomatic knee osteoarthritis, treatment with 5 leeches placed on the affected knee for up to 1 hour once weekly for 3 weeks provided improvements in pain, stiffness, and physical function that were not significantly different from 15 TENS treatment sessions.(Isik 2017)

A systematic review and meta-analysis of 4 clinical studies in patients with osteoarthritis of the knee (N=237) reported moderate to strong evidence for reductions in pain, functional impairment, and joint stiffness following leech therapy.(Lauche 2014) In another meta-analysis of adults with symptomatic knee osteoarthritis, medical leech therapy was associated with a significant reduction in WOMAC scores (used to evaluate functional restoration) compared with controls (P=0.013 at week 1, P=0.039 at week 4, and P=0.005 at week 7), without significant heterogeneity. Additionally, pain (as measured by visual analog scale [VAS]) was also significantly reduced with medical leeches compared with controls at weeks 1, 4, and 7 (P=0.004, P=00.39, and P=0.033, respectively), without heterogeneity. Incidence of adverse events was significantly higher with leech therapy than controls (P=0). The quality of evidence was moderate for each outcome and overall.(Wang 2018)

A saliva extract from H. medicinalis formulated into a liposomal topical gel was tested in patients with knee osteoarthritis (N=60). Pain VAS scores were reduced approximately 50%, while Lequesne Index scores doubled for distance walked and increased from 8.5 to 18.9 for daily life activities.(Shakouri 2018)

Periodontitis

Clinical data

In patients with chronic periodontitis, 6 to 8 applications of hirudotherapy added to standard therapy resulted in greater decreases in inflammation and bleeding, by as much as 24% in patients with moderately severe disease compared with reductions of 6% and 2% in patients with severe and mild disease, respectively.(Sashkina 2019)

Skin conditions

Clinical data

Resolution of cutaneous leishmaniasis with hirudotherapy has been reported in 2 Iranian patients: a 56-year-old man with a lesion refractory to 4 months of antibiotic treatment and cryotherapy and a 43-year-old woman with a facial lesion of 6 months' duration. Lesions resolved after 2 months and 6 months, respectively.(Hamidizadeh 2017)

A 25-year-old immunosuppressed woman with a 7-year history of giant plantar warts refractory to many pharmaceutical and destructive treatment methods self-applied medicinal leeches to her feet. Within weeks, the warts decreased in size; within days of a second leech application 1 month later, the warts completely resolved.(Aktas 2020)

Wound healing

Clinical data

A pilot study (N=3) assessed benefit of hirudotherapy for treatment of nonhealing wounds. Both pain relief and healing of wounds were significant after as few as 2 applications.(Nair 2020)

Dosing

Institutional guidelines may exist and should be consulted for recommendations regarding the use of leeches. Feeding is complete in approximately 20 minutes, at which time the leech drops off. Removal of the leech may be hastened by applying solutions of salt, vinegar, a flame, or a local anesthetic; leeches should not be forcibly removed. Bleeding from the attachment site usually continues for several hours. Reuse of leeches is discouraged to minimize the development of cross-infection.(Abrutyn 1988, Adams 1989, Rao 1985, Whitaker 2005)

Results from a retrospective study (N=50) combined with data from 6 other studies and case reports focused on hirudotherapy along with associated antibiotic prophylaxis. Leech-related infections led to the development of the following standard protocol at a university hospital to optimize treatment, safe use, and secure disposal of the biohazardous leeches:

• Storage and dispensing. Management of leeches is assigned to the pharmacy, which allows for better control and traceability in the case of a nosocomial infection. Storage in a regularly decontaminated jar reduces leech-related infections by half compared to storage in a surgical unit in a jar not decontaminated regularly. The application and disposal protocols along with an empty disposal jar are also provided along with the dispensed leeches.

• Antibiotic prophylaxis with ciprofloxacin 500 mg twice daily was chosen based on local antibiogram and results from the literature review that demonstrated the importance of antibiotic prophylaxis (14% infection rate after hirudotherapy). The most commonly used antibiotics reported in the literature were 3^rd generation cephalosporins, fluoroquinolones, and sulfamethoxazole/trimethroprim.

• External decontamination before leech application was decided against; no studies supported its effectiveness.

• Iron supplementation is based on monitoring complete blood counts and platelets daily for 5 days and is to be administered by the IV route to avoid drug interactions between oral iron and ciprofloxacin.

• Application. The application protocol, which is dispensed by the pharmacy along with the leeches, is determined by the leech supplier and developed to ensure non-traumatic and hygienic handling of the leeches.

• Disposal. Leech disposal takes place in the care unit using the empty jar and disposal protocol dispensed by the pharmacy along with the leeches.(Vaesken 2022)

Pregnancy / Lactation

Information regarding safety in pregnancy and lactation is lacking. Avoid use because of risk of infection and anemia.

Interactions

None well documented. Closely monitor conditions requiring concomitant anticoagulant therapy.

One study found no changes in ipsilateral activated partial thromboplastin or prothrombin times when leeches were applied to an intact hand. This suggests that systemic or local anticoagulation is not likely to occur and that the risk of interference with other therapies may be small.(Blackshear 1994)

Adverse Reactions

Arterial insufficiency, previous exposure to leeches (risk of allergic reaction), immunosuppression (risk of infection), patient refusal to accept possible subsequent blood transfusions, and unstable medical conditions have been described as contraindications for extensive leech therapy.(Chepeha 2002)

Local allergic reactions and anaphylaxis have been reported.(Tseng 2005) Leeches found in the nose, throat, and GI tract have caused complications.(Bergua 1993, Krüger 2004, Kuehnemund 2006, Uygur 2003) Acute coronary syndrome associated with allergy, hypersensitivity, or anaphylactoid reactions (Kounis syndrome) was reported in a 41-year-old female immediately after leech therapy was administered for left knee aches; the patient presented with sudden onset of face and lip edema, shortness of breath, and chest pain.(Cakmak 2018) A case of cutaneous lymphoid hyperplasia was reported as a reaction to one application of leeches.(Sadati 2019)

Leeches may consume up to 50 mL of blood per application, and their secretions during a single feed can prevent coagulation (in vitro) of up to 100 mL of human blood. Passive bleeding after detachment most commonly continues for approximately 5 hours but can continue up to 72 hours. Blood loss may occur, sometimes requiring transfusions.(Ikizceli 2005, Porshinsky 2011) Approximately 90 mL of blood had to be aspirated via arthrocentesis from the knee joint of a 58-year-old male with diabetes who had undergone hirudotherapy on his injured knee 1 week earlier in an effort to reduce persistent pain subsequent to a fall 6 weeks previously.(Curcio 2020) Another patient with a history significant for hypertension, diabetes, diabetic foot, ischemic heart disease, and coronary artery bypass graft developed nonocclusive acute mesenteric ischemia within 2 hours of leeches applied to both feet to treat diabetic foot wounds. The terminal ileum and entire colon were necrotic. An end-ileostomy was performed, and the patient recovered.(Akalın 2020)

H. medicinalis should be considered a possible vector of infectious diseases. The incidence of infection consequent to leech therapy ranges from 2% to 20%.(Elyassi 2013, O'Dempsey 2012) The gram-negative Aeromonas hydrophilia is the predominant microbial species found in leeches.(Ardehali 2006, Chepeha 2002, Steer 2005, Whitaker 2005) Serratia, Klebsiella, and Pseudomonas have also been isolated,(Bickel 1994, Dickson 1984, Dippenaar 2006, Kourt 1994, Wilken 1993) and patients should receive appropriate prophylactic antibiotic therapy. Older studies suggest possible transmission of HIV and hepatitis, but this is less likely with the use of farmed leeches.(Nehili 1994, O'Dempsey 2012) Reuse of leeches is not recommended due to concerns of disease transmission.(Whitaker 2004)

Several cases of cutaneous pseudolymphoma subsequent to leech therapy have been reported. The lesions typically appeared as pruritic red lesions in the area of leech application that persisted for months and resolved with either intralesional, intramuscular, or oral plus topical corticosteroid treatment.(Sepaskhah 2020, Temiz 2019, Tupikowska 2018) Lichen planus thought to result from hirudotherapy was also reported in a patient with pruritic, purple-colored lesions on his legs at the site of leech application as well as white patches in his mouth and purple patches in areas unrelated to leech application (ie, abdomen, forearm, sacrum, penis). The rash resolved with oral and topical methylprednisolone plus levocetirizine.(Daye 2021)

Toxicology

No data.

References

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