Continuing Education Activity

Leeches are hermaphroditic parasites of phylum Annelida and class Hirudinea. There are over 600 species of leeches. A minority of these are sanguinivorous and the cause of human morbidity. Historically, leeches have been used for medicinal purposes with the earliest recorded being 1500 BC. Leeches have continued to be used in modern medicine primarily in reconstructive surgery. This activity reviews the pathophysiology of leech bites and highlights the role of the interprofessional team in its management.

Objectives:

• Review the toxins present in leech saliva.
• Describe the presentation of a patient with a leech bite.
• Summarize the treatment of a leech bite.
• Outline the importance of improving care coordination among interprofessional team members to improve outcomes for patients affected by leech bite.

Introduction

Leeches are hermaphroditic parasites of phylum Annelida and class Hirudinea.[1] There are over 600 species of leeches. A minority of these are sanguinivorous and the cause of human morbidity. Historically, leeches have been used for medicinal purposes with the earliest recorded being 1500 BC. Leeches have continued to be used in modern medicine primarily in reconstructive surgery.[2][3][4][5] An adult leech can ingest 1 milliliter per minute of blood, and the area of attachment can bleed for 10 hours to as long as 7 days in some instances. Land leeches can penetrate thick skin, while aquatic leeches attach to mucous membranes leading to prolonged bleeding. Leeches are used intentionally in reconstructive surgery where a flap or replanted digit has developed venous congestion. The leeches drain the excess venous blood, increasing the chances of survival of the flap or replant.

Etiology

Leach bites may be due to swimming or bathing in leech infested waters or by deliberate placement for reconstructive surgery.[6][7]

Epidemiology

Limited information is reported regarding leech bites, and the majority of case reports are from the tropics or subtropics and occur after contact with fresh water. Vaginal leech bites in children are reported commonly in rural north-eastern India. [8][9][10][11]Sanitation advances have led to decreased incidence of nasal leech infestation in developed nations. In one review of six patients with nasal leeches, all patients had been in rural streams 2 weeks to 2 months before symptoms occurred.

Pathophysiology

Leech bites primarily occur while bathing or drinking unfiltered water or while swimming in contaminated water. A leech has an anterior oral sucker as well as a posterior sucker. The anterior sucker is used for feeding.[12] The leech releases an anesthetic on attachment to the host to prevent the host from recognizing the parasite is attached. The saliva of leeches contains hirudin, a potent anticoagulant. This results in prolonged bleeding from the leech bite, allowing the organism to feed but also resulting in prolonged bleeding once detached.

Toxicokinetics

Leech saliva contains numerous substances including hirudin (potent antithrombin), hyaluronidase, histamine-like vasodilator, and calin (a platelet aggregation inhibitor).[13] Hirudin from leech saliva can take hours to wear off. It is a peptide that inhibits the thrombin-catalyzed conversion of fibrinogen into fibrin clots and remains active for 15 to 20 minutes.[14] Leech attachment sites may bleed more than normal wounds and can continue to bleed after removal of the leech.

History and Physical

A detailed history needs to be obtained, including any recent exposure to fresh water. While most leech bites are external, leeches can attach internally, and patients will present with epistaxis, hematemesis, hemoptysis, vaginal bleeding, hemoptysis, otorrhagia, and rectal bleeding. When the leech bite is external, patients' symptoms may include painless bleeding, bruising, itching, burning, irritation, and redness. Patients may present with recurrent epistaxis if they have a nasal leech infestation. 

A focused physical exam will be required depending on the area of concern. If there is a concern for a nasal leech infestation, examination with anterior rhinoscope is not sufficient, and inspection with an endoscope is usually necessary. When there is the concern for vaginal leech infestation, a speculum exam is required. Depending on the age of the patient, this may need to be done under anesthesia. A rectal exam with a proctoscope may be indicated for a patient presenting with rectal bleeding in the setting of concern for a leech bite.

Evaluation

Most leech bites will not significantly alter coagulation pathways, although case reports do exist where prothrombin (PT) and partial thromboplastin time (PTT) times were affected. If there is a concern for a significant amount of bleeding, a complete blood count (CBC) may be obtained. Leech attachments can cause significant bleeding leading to acute blood loss anemia. Imaging typically is not necessary as the leech is often found on physical exam. However, if suspicion remains for a leech infestation imaging of the area of concern may be necessary. One case report discussed the presentation and treatment of an intraperitoneal leech which was seen on abdominal ultrasound and another report described a leech which was seen over the left nasal cavity on computed tomography (CT) scan.

Treatment / Management

Initial treatment should include removal of the leech or leeches, controlling blood loss, and preventing exposure to blood-borne pathogens.

Various methods of leech removal have been utilized including salt, saline, vinegar, turpentine, alcohol, and heat. Chemical methods have also been used including cocaine, lidocaine, and topical anesthetic spray. Of these, saltwater has been shown to be effective in causing the leech to relax and release. Extra caution should be used when removing the leech as to not have reflux of contents back into the bite for risk of infection as well as increased bleeding. [15][16][17]Caution should be exercised to prevent the jaws from remaining in the wound for the risk of continuous bleeding.

Leech removal often requires unique situational removal techniques based on the location of the leech. A 2-year-old was found to have an intrabdominal leech which had perforated her uterus, and it required exploratory laparotomy for removal. A case report discussed a 24-year-old male with a leech bite in the external ear canal near the tympanic membrane with bleeding from the ear. Lidocaine 2%, then hypertonic saline was placed into the ear without decreased movement of the leech. Next, the glycerin phenique was placed into the ear. The movement of the leech decreased, and the bleeding ceased after 4 hours. After the bleeding had stopped, the leech was removed with alligator forceps. When trying to remove a leech from the vagina of a pediatric patient, normal saline flushed through a small feeding catheter has been reported with success.

After removing the leech, the wound must be cleaned, and bleeding must be stopped. Betadine or topical antibiotic agents can be used to clean the wound. A hemostatic agent or bandage can be used in addition to a pressure dressing to help with hemostasis. Cauterization, local application of tranexamic acid, silver nitrate, suturing of wounds, and tampon use have all be described as methods for achieving hemostasis after a leech bite.[18] Case reports exist where blood product infusions have been required. Tranexamic acid has also been used to achieve hemostasis.

Bacteria of the genus Aeromonas reside within the gut of the leech, and reports of infection after leech therapy have been reported. Prophylactic antibiotics directed at this species are recommended after leech exposure, whether intentional or incidental.

Differential Diagnosis

• Erysipelas

• HIV infection and AIDS

• Impetigo

• Mantle cell lymphoma

• Millipede envenomation

• Pediatric anaphylaxis

• Rattlesnake envenomation

• Poisoning by plant resin

• Scabies

• Scorpion envenomation

Complications

Leeches are carriers of viruses and bacteria. HIV and Hepatitis B were isolated from live leeches pulled from fishermen in Africa.[19] Viruses may remain in leeches for as long as 5 months. Studies have also shown that malaria is capable of replicating in the red blood cells that a leech ingests. Leeches carrying infectious diseases have also been found in medicinal leeches with reports of 2.4% to 20% infection rate during medicinal leech therapy.[20] The majority of these infections were caused by Aeromonas hydrophila which can be treated with fluoroquinolones, although resistant strains exist.[21][22][23][22] It may be reasonable, after weighing risks and benefits, to offer the patient antibiotics after a leech bite.

Deterrence and Patient Education

Prevention of leech bites includes avoiding leech infested areas and wearing clothing that covers the lower extremities. If swimming in a potential leech-infested pond, wear tight-fitting swimwear. Insect repellents such as N, N-diethyl-meta-toluamide or N, N-diethyl phenylacetamide have also been suggested.

Enhancing Healthcare Team Outcomes

The management of leech bites is with an interprofessional team that includes an emergency department physician, nurse practitioner, primary care provider, and an infectious disease consultant. There are many methods of removing leeches and overall the outcomes are excellent.[24] 

However, leeches are known to carry a variety of viruses and bacteria that may cause a systemic infection. The decision to treat the patient with antibiotics requires good clinical judgment. The key is to educate travelers on how to prevent leech bites. This may be done by wearing appropriate clothing while in the water and using insect repellants. [24]