Leech Farm

• Feeding
Most leeches do not feed on human blood, but instead prey on small invertebrates, which they eat whole. To feed on their hosts, leeches use their anterior suckers to connect to hosts for feeding, and also release an anesthetic to prevent the hosts from feeling them. Once attached, leeches use a combination of mucus and suction to stay attached and secrete an anticoagulant enzyme, hirudin, into the hosts' blood streams. Though certain species of leeches feed on blood, not all species can bite; 90% of them feed solely on decomposing bodies and open wounds of amphibians, reptiles, waterfowl, fish, and mammals (including, but not limited to, humans). A leech attaches itself when it bites, and it will stay attached until it becomes full, at which point it falls off to digest. Due to the hirudin that leeches secrete, bites may bleed more than a normal wound after the leech is removed. The effect of the anticoagulant will wear off several hours after the leech is removed and the wound is cleaned.
Leeches normally carry parasites in their digestive tracts, which cannot survive in humans and do not pose a threat. However, bacteria, viruses, and parasites from previous blood sources can survive within a leech for months, but only a few cases of leeches transmitting pathogens to humans have been reported. A study found both HIV and hepatitis B in African leeches from Cameroon.