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Leeches Invade Japan

Leeches Invade Japan

By B. James McCallum and Stuart M. Smith

Imagine not being able to walk out the front door of your house without being attacked by Nosferatu. This has become a reality for many residents of Japan. The type of large land leech, known locally as yamabiru, is leaving the mountains and invading suburbia.

Although it sounds absurd, the leech invasion is forcing the closure of campsites and is changing the way that farmers grow rice and tea – some have even been forced to abandon their livelihood.

The leeches attach themselves painlessly to people and begin sucking blood, swelling from their normal length of 1.5 cm to up to ten times that size before becoming sated. Often their victim does not even realize that the leech is present until they notice their clothing soaked with blood.

No one is quite sure why the leeches have given up there mountain homes for suburban Japan, but there is speculation that strict hunting regulations have increased the number of wild animals that are there usual prey. Furthermore, a decrease in deforestation near inhabited area has also allowed the surplus animals to live in closer proximity to humans. The blood suckers have followed suit. Global warming may also have decreased the number of animal dying from exposure each year.

There seems to be no good way to stop the leech invasion. Communities have erected fences to keep the deer and wild boar away and have sprayed pesticides for the leeches, but they still keep coming.

Leeches were used for hundreds of years in European medicine as a way to remove blood from sick individuals. They are still used today in certain situations where a small prescribed amount of blood needs to be removed from an area – say from a finger that has been reattached after having been cut off. A component of leech spit, the chemical hirudin, has unique blood thinning properties. There are several synthetic versions of this protein in use in modern medicine today.

Get more from James and Stuart with their excellent review of gummy bear science, alternatively try these stories:

- Top ten - World's grimmest parasites
- Rubber Invaders - Britain braced for a ducking
- Little swine - Blood-sucking creatures
- Killed by poo - Ancients tribe's fatal faeces

Image via Dierdorf

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28 Jul 2009
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