leeches & health – asking some questions

This morning’s Herald ran an article on ‘alternative therapies’ – New Zealanders’ beliefs about their effectiveness, & a Herald reporter’s experience of one such ‘therapy’. (Apparently there will be more to come over the next few days.) The article presented some results from a recent UMR research poll – as it was provided ‘exclusively to the Herald’ I wasn’t able to read the whole thing – which apparently show that around 75% of those surveyed believe that arnica reduces bruising (which it may well do, provided we’re talking therapeutic & not homeopathic concentrations), while 51% believe that homeopathy has been scientifically proven. Sigh. (The article also cited a 2008 Massey University study, which I wrote about at the time it came out.)

So I suppose I shouldn’t have been surprised to read on & find that the reporter who tried hirudotherapy (ie blood-letting using medicinal leeches) didn’t actually question any of the claims made for this particular treatment modality.

Apparently, ‘leech therapy’

has "gone global" since Greek physician Nicander in Colophon was recorded as using them in 200 BC.

Well, yes – leeches have a long history of medical use. Much of this was at a time when people believed things such as health being a matter of balancing the four ‘humors’, and that imbalances could be dealt with by bleeding the patient. This could be done using either a scalpel, or a leech. Given that the germ theory of disease was well in the future & standards of surgical hygiene rather limited, I would have gone for the leech every time. Although – there would still be the risk of picking up a real blood-borne illness from the last patient to be sucked on (see below). However, leeches have come back into favour & are used in some aspects of mainstream medical practice.

The practitioner featured in this article told the reporter that

medical leeches can treat problems ranging from arthritis, diabetes, endometriosis, hepatitis and high blood pressure to bronchitis.

"Their saliva has enzymes that helps break blood clots, and widens blood vessels to stop bacteria growth and present inflammation. It also helps blood circulation and flow," he said.

Leech saliva does contain a rich mix of chemicals, as you’d expect in a blood-sucker. After all, the last thing a leech needs is for your body’s normal blood-clotting cascade to kick in while it’s dining, nor does it need local inflammatory responses as these would slow the flow of blood to the wound site. These constituents are listed in a 2007 article by Dr Karen Dente (emphasis mine)

  • Hirudin, a direct thrombin inhibitor;

  • Hyaluronidase, which increases the local spread of leech saliva through human tissue at the site of the would and also has antibiotic properties;

  • A histamine-like vasodilator that promotes local bleeding; and

  • A local anaesthetic.

Note the use of the word ‘local’. This is not the same as the systemic effects claimed above. Hirudin is used clinically as an anticoagulant – in controlled, measurable doses, which is not what you’re going to get by using individual leeches.

What about these claims of the problems leeches can be used to treat? (It would have been nice to see the reporter asking this!) While it’s possible that a leech’s kiss might have some impact on circulatory issues, what about bronchitis? Hepatitis? Diabetes?

I can actually think of a potential mechanism for their use in treating some of the sequelae of diabetes, where peripheral circulation may be reduced. But how on earth is leech saliva going to address the root problem with diabetes ie the body’s inability to produce (Type 1) or to respond to (Type 2) insulin? Certainly a PubMed search turned up nothing for ‘leeches + diabetes’ (or ‘hirudo + diabetes’, come to that).

As for hepatitis, the various types are due to viral infections that target the liver. Off we go to PubMed again. It turns out that the virus that causes hepatitis B can persist in a leech’s gut for up to 15 weeks. This alone should rule out the use of leeches in anything other than controlled, use-once-and-discard circumstances. And again, there is nothing on PubMed relating to therapeutic uses of leeches for people with hepatitis. (Nothing, also, for bronchitis or endometriosis…)

The medicinal hirudo leeches, which are used at his clinic, can help reduce wrinkles and stimulate circulation in reattachment operations for organs with critical blood flow, he claims. "These creatures are God’s gift to nature, and nature’s gift to mankind to keep us in good health."

That’s a really strange juxtaposition – a minor cosmetic issue and a major surgical problem! Anyway, while it is indeed correct that leeches are used in reattachment operations where circulation is an issue (for example, reattachment of an ear), unless these leeches are used on a ‘once only & then discard’ basis, there’s the potential for bad health outcomes too, if a prior customer was carrying hepatitis…

NB neither antiquity nor popularity are, by themselves, a good indication that something actually works.


Over at Respectful Insolence, commenter lilady tells me that an Austrian version of hirudotherapy involves "bathing in turpentine, shaving certain areas of [the] body, and then letting the leeches suck your blood." One celebrity endorsing this ‘treatment’ says that "These are not swamp leeches, they are ‘highly trained’ medical leeches." 


I suspect the humour in this statement was not intentional. 

Leave a Reply

Your email address will not be published. Required fields are marked *