Leeches - the fleshy bloodsucking worms associated with the historic world of medicine - are making a comeback - even if the yuk factor means they often have to be hidden from public gaze.

A leech farm in Wales sells 15,000 leeches a year to the NHS, according to London medical student Robert Weinkove, who has written a history of the worm for the Student British Medical Journal.

Biopharm, a leech farm in Swansea, exports another 15,000 a year around the world.

Leeches were widely used up until this century for many medical conditions, including tonsillitis and piles.

"They went too far, overusing them and using them in the wrong way with little benefit, " said Mr Weinkove, a fifth-year medical student at the United Medical and Dental Schools of Guy's and St Thomas' Hospitals in London.

A few doctors were still using leeches in the 1930s and 40s, mainly on stroke patients, but their use died out until the 1960s when interest in the creature was reignited.

But it is only in the last 10 to 15 years that they have really caught on and their use has taken off in the last five years.

Image problem

Mr Weinkove believes it has taken so long for them to come back because they have an image problem.

People donate blood for medicinal purposes; leeches take it away...

"Doctors have been reluctant to use them because of their image, but now it has been proven that they can be useful in certain cases," he said.

Leeches are particularly useful in plastic surgery, such as breast reconstruction and where a part of the body has become severed and had to be sewn back on.

Sometimes, the patient's veins are too weak to take the blood away from the body part and the blood builds up, causing "venous congestion".

Attaching leeches to the body can draw the blood away gradually and painlessly since leech saliva contains an anaesthetic.

This allows the re-attached body part to survive until the veins are strong enough to work normally. One man who cut off his penis had to have leeches attached to drain the blood.

Swollen

The leeches suck the blood until they become totally engorged. They can take in up to 10 times their bodyweight in blood. When they are full they fall off and can be replaced with another leech.

A patient may need up to 30 leeches to drain blood away.

Mr Weinkove says most patients are willing to have leeches on their bodies if it is a choice between leeches, more operations or losing a part of the body.

He says children often give them names. But their family and friends are not so keen to see the creatures at work.

This has led some doctors to hide the leeches, using dressings. Another consideration is to ensure the leech feeds on the right part of the body.

'Dinner plate'

Doctors in Philidelphia have developed a plastic shield to hide the leech and keep it in place.

It involves a dinner plate-like object with a hole in it. This is used on severed fingers. The patient's arm is covered in plaster of paris to keep it raised in the air so the blood can be drained.

The dinner plate is put on top and the leech is attached and covered in fabric. One of the doctors involved is called Dr Callegari, conjuring up images of the famous German film.

Most hospitals in the UK which use leeches do not keep them on site when there is no specific need for them.

There are a handful of pharmacies up and down the country which have storage room for them. They can send leeches over to hospitals on request.

Leech saliva also has medicinal uses of its own. It prevents clotting and is being used in several new drugs, for example, to treat patients who have had a stroke, often due to blood clots in the brain.

A new one, hirudin, is being used in the US and may have less side effects than other anti-clotting drugs.