• Question from:Wesley

I read that leeches are still used in medicine.  Is it possible to catch something from them if they are used on people? And what chemical in leeches is it that helps a sick person?  Thanks.

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  • University of Western Australia, Perth
  • Posts: 96

Hirudotherapy is the use of medicinal leeches for medical purposes.  The most common leech used in medicine is Hirudo medicinalis.  The medicinal use of leeches was described by the Greeks as far back as 200BC and originally they were used to remove blood with the aim of restoring the balance of the 4 humors.  They have also been used to treat skin diseases and clean up surgical wounds after operation.  In fact, in 19th century France the esteemed physician Francois Broussais rejected the humoral theory of disease, but favoured extensive bleeding as therapy. So convincing were his teachings that the physicians of France imported in a single year over 40 million leeches!

Today they have been used in association with microsurgery, to reduce blood coagulation (clotting) and relieve venous pressure.  The therapeutic effect does not only come from the blood taken in the meal, but also, the continued bleeding after the leech is detached, which is due to the anticoagulant (hirudin) in the leeches saliva.

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  • University of the Pacific, California, USA
  • Posts: 122

Bloodborne diseases can indeed live on in a leech if they feed on an infected person.  In general, after microsurgery assisted by leeches the animals are discarded and not used again on another patient.