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The taxonomy of what has until recently been considered as a single species, Hirudo medicinalis, has been revised dramatically during the first decade of the 21st century (Trontelj and Utevsky 2012 and references therein). In fact, it appears there are three species of European medicinal leeches and that most commercial and aquaculture specimens actually belong to the Eastern phylogroup of H. verbana, presumably due to the fact that commercial facilities obtain leeches from Russia and Turkey, the major leech exporters (Siddall et al. 2007; Kutschera 2012; Trontelj and Utevsky 2012). True Hirudo medicinalis is the northernmost species among medicinal leeches. It occupies the deciduous arboreal zone from Britain and southern Norway to the southern Urals and probably as far as the Altai Mountains (Trontelj and Utevsky 2012).
Siddall et al. (2007) note that some researchers see therapeutic potential for many protease inhibitors purified from leech saliva, and that, notwithstanding the historical association with quackery, Hirudo medicinalis has been approved by the United States Food and Drug Administration as a prescription medical device (although most leeches being used therapeutically are apparently H. verbana). Whitaker et al. (2012) reviewed available evidence on the efficacy of medicinal leeches in plastic and reconstructive surgery (mainly to prevent venous congestion) and presented what they considered to be current best evidence to guide clinicians. Yantis et al. (2009) provided guidelines for nurses for the safe and effective use of leeches.The use of leeches is not without risks, such as serious wound infection, but many medical practitioners and researchers believe the benefits often outweigh the risks and that risks can be minimized (e.g., with the use of prophylactic antibiotics).