Leeches (Common Blood-suckers)

Leeches move through the water by undulating like a snake. They can also move along the surface of an animal, rock or piece of wood by ‘looping’. They do looping by attaching their mouth to a surface, pulling their body forward and attaching their tail suckers to the surface. By repeating this looping motion they can move over a surface.

Most leeches have well developed jaws with gristly mouthparts to break through the skin of their victims and suck fluids. Their saliva contains an anesthetic (pain killer) so their victim does not feel them break the skin. Their saliva also contains an anticoagulant (a chemical that stops the blood from turning jellylike and scabbing) called ‘hirudin’. Leeches have very large ‘crops’ that make up most of their digestive organs. The ‘crop’ can hold up to three times the weight of the leech in blood. The leech keeps only the solid parts of the blood as food. While it is sucking and after it leaves the host or prey, the leech’s kidneys eliminate or rid its body of the fluid part of the blood.

If you or a friend finds a leech on your skin, it is important to not pull it off. The leeches’ mouthparts could be left in your skin and cause infection. Infection is more dangerous than the loss of blood. Get out of the water. Use an irritant like salt or heat (lighter, match, hot pin) to make the leech let go and drop away.
Clean, disinfect and bandage leech bites. Treat the bite similar to any other cut. Although there is no evidence that leeches transmit disease, if not treated properly the wound may become infected.

A leech bite may continue to ooze for several hours after the leech is removed. This is caused by compounds present in leech saliva which prevent blood from clotting. Although troublesome, this normally does not result in any significant blood loss.

There may also be delayed irritation or itching after a bite. Allergic reactions have also been reported in some cases. If the wound does not appear to be healing properly or you experience any further discomfort, contact your doctor.

If you believe that there is a persistent problem with leaches at lake swimming beach that may represent a public health hazard, please contact both the Water Quality Program at (360) 337-5245 and the owner/operator of the beach.