Oregon’s diverse freshwater environments, from serene lakes to winding rivers, are home to a variety of aquatic life, including leeches. These segmented worms are found across Oregon’s aquatic ecosystems, an integral part of the natural food web.
Leeches Native to Oregon
Leeches are annelids, closely related to earthworms, belonging to the subclass Hirudinea. While nearly 700 species exist globally, various species inhabit Oregon’s freshwater habitats. Most do not feed on human blood; many are predatory, preying on small invertebrates like snails and insect larvae, or act as scavengers. Some parasitize fish, amphibians, or other vertebrates.
Surveys in regions like the mid-Snake River have identified species such as Erpobdella parva, Mooreobdella microstoma, and Helobdella stagnalis. A new Placobdella species was also discovered in Deschutes County, Oregon, feeding on frogs. These leeches secrete hirudin, a potent anticoagulant, a characteristic of blood-feeding species.
Oregon Leeches and Their Habitats
Leeches in Oregon commonly inhabit freshwater environments, including lakes, ponds, slow-moving streams, marshes, and wetlands. They prefer shallow, protected waters, often found concealed among aquatic vegetation or underneath submerged stones, logs, and other debris. While some species exist in moist soil or damp vegetation, aquatic leeches are prevalent in areas with still or slow-moving water.
These creatures are attracted to disturbances in the water and are more active during warmer summer months. They are found in various Oregon waterways, such as the Siuslaw River, the Columbia River and its tributaries, and lakes like Marion Lake and Davis Lake. Their presence is a natural indicator of a healthy aquatic ecosystem.
Understanding Leech Encounters
Encountering a leech can be unsettling, but most North American species are not considered dangerous to humans. When a leech attaches, it injects an anesthetic, making the bite painless and often unnoticed initially. They also release an anticoagulant into the wound to prevent blood clotting, leading to prolonged bleeding after detachment. This bleeding can last from several hours to a few days.
After a leech detaches, the bite site may show bleeding, itching, burning, irritation, and redness. While the risk is low, improper removal or scratching the bite can introduce bacteria, such as Aeromonas, leading to a localized infection. Allergic reactions to leech saliva are rare. Leeches are attracted to body heat and movement, which helps them locate a host.
Safety and Removal Guidelines
Preventing leech attachments involves precautions when in or near freshwater environments. Wearing protective clothing, such as long pants tucked into socks or boots, creates a physical barrier. Avoiding stagnant or murky water and routinely checking your skin after water activities also helps prevent encounters. Applying insect repellent containing DEET to exposed skin and clothing can deter leeches.
Should a leech attach itself, remaining calm is important. Avoid pulling, burning, or applying salt to a feeding leech, as these methods can cause the leech to regurgitate its gut contents into the wound, increasing the risk of infection. The safest way to remove a leech is to locate its head, which is the narrower end. Gently slide a fingernail, credit card, or another thin, blunt object under the leech’s mouth to break its suction. Once the head detaches, dislodge the posterior sucker and flick the leech away.
After removal, thoroughly clean the bite area with soap and water or an antiseptic. Apply pressure to stop any bleeding and cover the wound with a sterile bandage, changing it as needed. Monitor the site for any signs of infection, such as increased redness, warmth, or pus.