At present, the bloodsucking leeches which are widely distributed in China and easy to collect for medical treatment are: Japanese medical leeches, Philippine leeches, Hainan leeches, Tianmushan leeches and so on. However, the most common leech on the market, the wide-body golden leech, does not suck blood, but feeds on the body fluids of mollusks such as snails. The biggest difference in appearance between bloodsucking leeches and non-bloodsucking leeches lies in their size: bloodsucking leeches are small because of limited food sources, which can reach 1~5 times of their own weight at a time and can survive for one year, and their size changes greatly before and after bloodsucking, which can reach 2~5 times. Non-bloodsucking leeches have a wide range of food sources and do not need to store food in the body. Individuals are generally twice the size of their thumbs. Blood-sucking leeches hide when they are full and rarely move, so body shape is the most basic way to distinguish blood-sucking leeches from non-blood-sucking leeches.

Humans have used leeches to treat diseases for 3000 years: the murals in the tombs of ancient Egyptian pyramids have already burned the story of ancient humans using leeches to treat diseases. In Europe, doctors in the Middle Ages always used leeches to treat thromboembolism, which became a fashion in the19th century. At that time, leeches were very popular and almost disappeared in Europe. China recorded leech medicine for the first time in Shennong Herbal Classic more than 2000 years ago. Traditional Chinese medicine believes that it has the functions of breaking blood, removing blood stasis and dredging meridians. It is mainly used to treat tumor, swelling, blood stasis, amenorrhea, traumatic injury and so on, and is still widely used in internal medicine, surgery, gynecology, andrology and dermatology of traditional Chinese medicine. /kloc-In the late 9th century, with the development of modern physiology, pathology and microbiology, and more and more reports of infection and excessive bleeding related to leech therapy, many scholars believe that leech therapy has no place in modern hospitals. However, since the appearance of microsurgery and tissue transplantation in 1960, there have been more and more reports about the failure of using leeches to save transplanted flaps. In the reconstruction of local congestion after microsurgery, the current medical methods are sometimes powerless, but leech therapy is unique. The medical value of leeches has been rediscovered. 1985, Joseph Upton from the Department of Plastic Surgery, Harvard Medical Center performed vascular anastomosis and replantation for a patient 1 5 years old whose ear was completely severed due to dog bite. After operation, leech therapy was used to relieve venous congestion and rebuild circulation. The success of this operation re-established the position of leech therapy in modern medicine, and greatly increased the sales of leeches of BIO—PHARM Company in Britain. L Scott Levin, director of plastic surgery at Duke University Medical Center in the United States, commented that leech therapy is an ancient and effective treatment method, and it is a living drug therapy for some patients in a specific L clinical state [13 1. At present, plastic surgeons in Britain are still using leech therapy to save failed flap surgery. A survey of 62 plastic surgery institutions in Britain shows that most plastic surgery institutions use leech therapy after surgery. In June 2004, FDA approved that medical leeches can be sold publicly, and synthetic hirudin can be used for clinical treatment of some indications. The Russian Ministry of Health recently officially approved some leeches for clinical treatment of coronary heart disease, angina pectoris and myocardial infarction.