Leprosy (Hirudinea) is a class of ringworms. Its body length is from a few cm to 15 cm, sometimes even longer. The body is flattened on the back and abdomen, sometimes cylindrical, with 33 outer rings. The number of outer rings of the body 3 is not equal to the number of inner rings, usually each outer ring has 3-5 outer (secondary) rings. About 400 species are distributed in freshwater basins and seas. Most leopards have two suckers, one in front of them and the other behind them. The mouth is lined with a sucker or Khartoum. Leeches live in the wild (leeches) or parasites (leeches). The leech feeds on small invertebrates, and the parasitic leech sucks the blood of various vertebrates and humans. The leech sucks a lot of blood into the very large sacs on the side of the intestine. The hirudin in leprosy does not clot the blood. Leeches breathe through their skin. Digestive system - metanephridia. The circulatory system of the leech differs from other roundworms in that it has no vascular wall epithelium, and the blood vessels are formed by the remnants of the body cavity. Leeches are hermaphroditic, laying their fertilized eggs in cocoons. The larva develops within the cocoon without change. 2 subclasses: ancient (Archihirudinea) and true leech. (Euhirudinea). True leeches are divided into Rhynchobdellida and Gnatobdellida. Hirudamedicinalis is used in the treatment of vascular diseases associated with thrombus formation (hypertension, early stages of sclerosis, stroke, etc.).Medical leprosy is propagated in special plants. Some leeches cause serious damage to fish. The Central Asian watershed is home to the Glossiphoniacomplanata, the Haemopissanguisida, and the Limnatusturkistanica. In the tropical forests of Ceylon and the Sunda Archipelago, the terrestrial leech (Haemodipsaceylomca) asked for human and mammalian blood.