Leeches are aquatic invertebrates found in freshwater environments across Massachusetts. These segmented worms are a natural component of many aquatic ecosystems. Understanding their presence and behavior can help alleviate concerns.
Leeches in Massachusetts
Massachusetts hosts various leech species, including the widespread American Medicinal Leech, Macrobdella decora. This species can grow quite large, sometimes exceeding nine inches, and is frequently encountered in coastal areas. The New England Medicinal Leech, Macrobdella sestertia, is also found, though it is rare.
Leeches inhabit slow-moving freshwater bodies such as ponds, lakes, and streams. They are often found in shallow waters with dense vegetation, or concealed under stones, logs, and other submerged debris. Their activity peaks during the spring and early summer months, often remaining hidden by day and becoming more active at night.
Many leeches are sanguivorous, meaning they feed on blood, but most do not target humans. For example, Macrobdella decora primarily feeds on fish, frogs, turtles, and certain mammals. The New England Medicinal Leech also feeds on amphibians, and possibly fish and amphibian eggs. Blood-feeding leeches release an enzyme to numb the area and prevent clotting, allowing for a steady flow.
Handling Encounters and Prevention
If a leech attaches to your skin, remove it carefully to prevent leaving mouthparts or causing regurgitation, which could lead to infection. Instead of pulling directly, gently slide a fingernail, credit card, or paper underneath its head end to break suction. Once the head is detached, repeat for the rear sucker, then quickly flick the leech away to prevent reattachment. If safe removal is not possible, the leech will detach on its own within 30 to 45 minutes once it has finished feeding.
After removal, clean the bite area with soap and water or an antiseptic to prevent infection. Because of the anticoagulant released by the leech, the bite may bleed for an extended period; apply gentle pressure with a clean cloth or bandage until bleeding stops. Monitor the wound for signs of infection, such as redness or swelling.
To reduce encounters, wear protective clothing, such as long pants tucked into socks or boots, in their habitats. Checking your skin after swimming or wading in freshwater helps identify attached leeches promptly. Avoid stagnant or murky waters with abundant vegetation to minimize direct contact. While leech bites are harmless and do not transmit diseases to humans, prolonged bleeding can occur, and allergic reactions are rare. Seek medical attention if you experience signs of infection or a severe allergic reaction.