Leeches are present across the United States. Understanding their habitats and how to interact with them can promote safety in outdoor environments.
Leech Presence in the US
Leeches are widely distributed throughout the United States, inhabiting diverse aquatic and some terrestrial environments. They are common in freshwater bodies such as lakes, ponds, slow-moving rivers, and marshes, thriving in shallow, vegetated areas that offer shelter and food sources. Terrestrial leeches, though less common, can be found in damp soil and leaf litter in humid regions, particularly in the southeastern US and Pacific Northwest.
The North American medicinal leech, Macrobdella decora, is found in much of eastern North America. Another species, Placobdella parasitica, is widely distributed in the eastern and north-central USA.
Understanding Leeches
Leeches are segmented worms belonging to the phylum Annelida, closely related to earthworms. Their bodies are typically flattened and muscular, ranging in size from millimeters to several inches, and they possess two suckers. The anterior sucker, located at the head end, is used for attachment and feeding, while the posterior sucker helps them anchor and move.
North America is home to over 650 species of leeches. While some are known for their blood-feeding habits, most species are predators, consuming small invertebrates like worms, snails, and insect larvae, or act as scavengers. Leeches move by either “looping” like an inchworm, using their suckers to pull themselves along surfaces, or by undulating their bodies to swim through water.
Addressing Leech Concerns
A leech bite is often painless due to anesthetic compounds present in the leech’s saliva, which they inject upon attachment. Following a bite, prolonged bleeding is common because leech saliva also contains hirudin, a potent anticoagulant that prevents blood from clotting. This bleeding can continue for several hours, or even days, after the leech detaches.
The risk of disease transmission from leeches found in North America is very low. While leeches can carry bacteria, particularly if they regurgitate gut contents during removal, direct transmission of serious human diseases is rare. Some leech species, like Hirudo medicinalis and Macrobdella decora, are used therapeutically in medicine, particularly in reconstructive surgery, due to their unique secretions that prevent blood clotting.
Prevention and Removal
To prevent leech encounters, wear protective clothing. Long pants tucked into socks and closed-toe shoes can create a barrier against leeches. Avoid wading or swimming in heavily vegetated or stagnant waters. Some insect repellents containing DEET may deter them. Regularly check your body, especially after being in moist environments, for early detection.
If a leech attaches, safe removal is important. Gently slide a fingernail or the edge of a credit card under the leech’s mouth to break its suction from your skin. Once the anterior sucker is dislodged, the leech can be flicked away. Avoid using harsh substances like salt, fire, or alcohol, as these can cause the leech to regurgitate stomach contents into the wound, increasing infection risk. After removal, clean the bite area thoroughly with soap and water, apply pressure to stop any bleeding, and then cover the wound with an antiseptic or antibiotic ointment and a bandage. Continue to monitor the area for any signs of infection, such as increased redness or swelling.