Medicinal leeches turn out to be misclassified

This video is called Hirudo medicinalis.

From the National Science Foundation in the USA:

Misclassified For Centuries, Medicinal Leeches Found To Be 3 Distinct Species

Science Daily — Genetic research has revealed that commercially available medicinal leeches used around the world in biomedical research and postoperative care have been misclassified for centuries.

Until now, the leeches were assumed to be the species Hirudo medicinalis, but new research reveals they are actually a closely related but genetically distinct species, Hirudo verbana.

The study also shows that wild European medicinal leeches are at least three distinct species, not one.

“This raises the tantalizing prospect of three times the number of anticoagulants, and three times as many biomedically important developments in areas like protease inhibitors,” said Mark Siddall of the American Museum of Natural History, who led the research team.

“However, it will also require a better effort to conserve these much-maligned animals, in a way that takes into account their impressive diversity.”

While Hirudo medicinalis was approved by the U.S. Food and Drug Administration (FDA) in 2004, for use as a prescription medical device that helps restore blood flow following cosmetic and reconstructive surgery, Hirudo verbana has not been approved by the FDA and has no special conservation status.

“This study is a great example of why the field of taxonomy [the science of classification of organisms] is so important,” said Patrick Herendeen, program director in the National Science Foundation (NSF) Division of Environmental Biology, which funded the research.

“Taxonomists have been studying the diversity of life on Earth for hundreds of years. In this case, the discovery of previously unknown species diversity has very significant legal and commercial implications.”

Since the time of Hippocrates and long before Carolus Linnaeus first described Hirudo medicinalis in 1758, medicinal leeches have been used in a variety of medical treatments–some legitimate, many not.

Demand for leeches in 19th-century Europe grew so intense that efforts to protect them led to the some of the earliest legislative efforts at biological conservation.

Leeches are still afforded protection by the World Conservation Union (IUCN) and are regulated by the Convention on International Trade in Endangered Species (CITES), the Berne Convention, and the European Union Habitat Directive.

Commercially available European medicinal leeches also are used extensively by biomedical researchers studying biological processes such as blood coagulation, developmental genetics and neurobiology.

Studies of commercial specimens have figured prominently in the discovery and production of anticoagulants and protease inhibitors, some of which may have cancer-fighting properties.

That researchers have been mistakenly using Hirudo verbana in their work for decades may call much of this research, including hundreds of scientific publications, into question and force a reconsideration of what scientists think they know about this widely studied species.

Siddall and his colleagues examined mitochondrial and nuclear DNA of wild leeches from across their range in Europe, as well as from samples supplied by commercial providers and university laboratories that use leeches as model organisms.

Their analysis clearly showed that the commercial and laboratory specimens were not Hirudo medicinalis, as they were labeled, but Hirudo verbana.

In addition, the work showed that the specimens of wild European medicinal leeches clearly comprised three genetically distinct species.

The results appear in the April 10, 2007, online version of the journal Proceedings of the Royal Society B.

The third species involved is Hirudo orientalis.

European land leech: here.

12 thoughts on “Medicinal leeches turn out to be misclassified

  1. 2007-05-07 11:03

    Friendly leeches to help doctors
    Italian study says they help deal with insulin resistance

    MILAN (ANSA) – Leeches are enjoying something of a medical comeback, with the latest Italian research suggesting they may be able to help combat diseases triggered by insulin resistance.

    A study by scientists at Milan’s Maggiore Policlinico hospital has found that leeches could play a vital role in helping combat problems such as cardiovascular disease.

    Insulin is normally released in the pancreas after eating, telling insulin-sensitive tissues in the body to absorb glucose in order to lower blood glucose to a normal level.

    In insulin-resistant people, normal levels of insulin fail to trigger the signal for glucose absorption and in order to compensate, the pancreas releases much more insulin.

    Insulin resistance is to blame for several problems, including damage to the liver, most commonly a fatty liver.

    Aggravated by a modern diet and sedentary lifestyle, a fatty liver is not life threatening but is painful and has been linked to an array of other problems, such as cardiovascular disease and some forms of diabetes.

    A variety of techniques has been developed to combat insulin resistance, most tending to involve the administration of drugs and pharmaceuticals. But the Italian study, directed by Silvia Fargion and published in the American Journal of Gastroenterology, adopted a far simpler approach.

    Working on the theory that an excess of iron can trigger insulin resistance, the team drew blood, which contains iron, using leeches.

    The treatment was carried out about eight times on 128 patients over the course of a year, combined with diet alterations and increasing physical activity.

    “Given that an estimated 20% of Italians suffer from fatty livers, this ‘ancient’ treatment could have an enormous impact in helping prevent cardiovascular disease,” explained Fargion.


    First used in Egyptian times, leeches have such ancient ties to the medical world that their modern name even comes from the Old English word for physician, “laece”.

    By the late 1800s they were used in the treatment of a variety of ailments, from headache to gout, based on the idea of draining “impure blood” from the body.

    Over the last couple of decades, doctors have returned to the bloodletting talents of leeches in limb reattachment operations.

    Arteries, which carry blood into the limbs, are fairly easy to suture as they are thick walled. But veins, carrying blood away, are far more problematic, meaning that patients often end up with blood congestion in the limb, making the surgery useless.

    This is where the leeches come in. Their three razor-sharp teeth latch onto the skin and draw blood out, while compounds in their saliva contain an anaesthetic that eases pain and stops the blood from clotting, allowing the blood to circulate freely.


  2. Marine leeches provide clues on climate change
    Tuesday, 17 June 2008, 10:09 am
    Press Release: Massey University

    Marine leeches provide clues on climate change

    Mr Kolb diving for leeches in the Arctic Ocean
    Full release with more pictures:

    Marine leeches provide clues on climate change

    Elusive marine leeches in Antarctica are the focus of study on how climate change is affecting vulnerable fish species.

    German-born doctoral researcher Juergen Kolb says it is proven that leeches transmit viruses and bacteria into host bodies, and that new strains are currently arriving in Antarctica.

    “The situation is potentially quite dangerous. If conditions become warmer, we’ll get new types of pathogens being transmitted into fish. Not only can this cause harm or death of individual fish but lead to the collapse of entire fish populations,” says Mr Kolb. “Eventually this could threaten commercial fishing industries and the food sources that humans depend on.”

    Based at Massey’s Institute of Natural Resources in Auckland, he is one of a handful of biologists world wide studying marine leeches.

    The bloodsuckers have generally been ignored by scientists because they are so hard to find and collect, he says. But gaining a better understanding of their biology and ecological importance could provide vital clues about the impact of climate change on fragile ecological systems and the survival of less adaptive animal species.

    Although little is known about marine leeches in extreme environments such as Antarctica, their physiology is thought to be similar to fresh water and terrestrial leeches in warmer habitats.

    Based on his earlier research on Arctic marine leeches, Mr Kolb says it is highly likely leeches will survive any rise in water temperature from global warming that would threaten other extreme cold water-adapted species more sensitive to change.

    Mr Kolb began his studies at the University of Freiburg. In 2006 he sailed on a Norwegian scientific research vessel to Svalbard Archipelago – halfway between Norway and the North Pole – where he dived up to 35 metres deep in freezing waters. But difficult conditions meant he was able to collect only seven leeches, which were attached to seaweed, algae, fish and crabs. He then decided to continue his research from New Zealand because of its accessibility to Antarctica. He hopes to gather a much greater quantity of leeches, this time by an easier method of catching leech-covered fish off the Antarctic coast. He will carry out genetic analysis on the leeches to determine how closely they are related to other leech species.

    Leeches, or Hirudinea, are a class of Phylum Annelida or segmented worms – most widely represented by the common earthworm. Leeches are divided into sections like an earthworm but with suckers at both ends. A leech is a thin tube of muscles around a cavity containing a gut and reproductive systems. It can flatten its body to avoid being removed from a host and, if necessary, swim in an undulating movement for kilometres.

    “I’ve always been fascinated by parasites,” says Mr Kolb. “They are extreme in terms of their physiology and adaptation to their parasitic lifestyle. They are, by nature, ultimate survivors – if you are a fish you have a hard time killing a leech.”


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