Effect of ale, garlic, and soured cream on the appetite of leeches

According to "The European" one of the most obscure clinical trials in contemporary medicine was recently conducted at our Department. Anders Baerheim and Hogne Sandvik sought to establish just what turns leeches on - or off. In 1996 Anders & Hogne were awarded the prestigeous Ig Nobel prize in biology for their scientific achievements.

The medicinal leech has regained some of its long-lost popularity by its present use in microsurgery. Sometimes, however, the leeches refuse to co-operate properly. To overcome this problem our colleagues of the past used to immerse leeches in strong bitter beer before application. An old deaconess learned that a little soured cream on the skin would encourage the leeches' feeding behaviour, and we recently found that they seem to be attracted by garlic. The present study, however, shows this to be a fatal attraction (abstract below).

OBJECTIVE — To evaluate the effect of ale, garlic, and soured cream on the feeding behaviour of leeches.
DESIGN — Controlled experimental setting. Leeches were randomized to different pretreatments (beer) or different preparations of the application site (soured cream or garlic).
SETTING — Division for General Practice, University of Bergen, Norway.
SUBJECTS — Two batches of six leeches each.
MAIN OUTCOME MEASURE — Time from application to biting one of the authors.
RESULTS — Leeches dipped in Guinness Stout bit after 187s, those dipped in Norwegian Hansa Bock bit after 136s, and the controls bit after 92s. Leeches exposed to soured cream bit after 25s (controls 34s). Two leeches briefly placed on a forearm smeared with garlic died after 2 ½ hours.
CONCLUSIONS — Beer disorganized the leeches' behaviour, skin contact with garlic proved lethal, while the effect of soured cream was uncertain.

You may want to read the whole story: Baerheim A, Sandvik H. Effect of ale, garlic, and soured cream on the appetite of leeches. BMJ 1994; 309: 1689.

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Department of Public Health and Primary Health Care, last updated 28.10.00