Genome of European Medicinal Leech (Hirudo medicinalis) Sequenced; Study Reports on 15 Different Proteins Known to Negatively Affect Blood-Clotting Mechanism in Vertebrates, 17 Others Likely Also Part of Same Anti-Clotting Process

The results of new research, published online on June 18, 2020 in Scientific Reports, reveal insights that may have profound effects on the use of medicinal leeches in hospital-based medicine. The open-access article is titled “Draft Genome of the European Medicinal Leech Hirudo medicinalis (Annelida, Clitellata, Hirudiniformes) with Emphasis On Anticoagulants.” An international team of researchers, led by Sebastian Kvist (, PhD, Royal Ontario Museum (ROM) scientist and Professor at the University of Toronto’s in the Department of Ecology & Evolutionary Biology, has announced the completion and results of their work to sequence the genome of Hirudo medicinalis, a European leech, and one of the most prominently used medicinal species. The team focused on the diversity of blood thinners--or anti-coagulants--contained within the genome, generating results that may have profound effects on how blood-sucking organisms are used in hospital settings. Medicinal leeches have long been used to treat various human conditions. However, their use in pre-modern medicine was based on early, unfounded theories of healing--primarily, that human body function relied on the balance of the four "humors": blood, phlegm, black bile, and yellow bile. Draining a patient's blood, often by applying live leeches, was thought to restore that balance. Today, two leech species--Hirudo verbana and Hirudo medicinalis--are used for healing practices based soundly in science, primarily for the replantation of digits (e.g., fingers) or skin grafting surgery. The saliva of these leeches contains the strongest blood thinners known to medicine and can relieve the buildup of blood after surgery and promote the healing of blood vessels.
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