Authorities in Madrid have declared war on a growing and formidable enemy - bed bugs that are infesting hotel rooms throughout the country at an alarming rate.

The government for the Madrid region has published a manual to make people and businesses more aware of the tiny pests and how to get rid of them.

The number of bed bugs actually declined in Spain in the 1950s and 60s.

But "today the situation seems to have completely changed, the declared number of cases has risen, in some cases quite significantly, approaching the level of an epidemic," said the manual, seen by AFP on Wednesday.

The bugs' dramatic reappearance coincides with the withdrawal from the market of powerful chemicals such as DDT, which killed the insects but were harmful for the environment.

As their name suggests, bed bugs are primarily found in mattresses and become active at night when they gorge on the blood of sleeping humans who are blissfully unaware that they are providing an impromptu midnight feast.

Until the next morning that is, when red welts show up on the victim's skin.

The flat, oval, brownish-red creatures, which measure about five millimeters, do not transmit any diseases.

But they leave traces of blood and feces on the pillows and sheets, and an infested room can have a unpleasant, pungent smell.

Their numbers rose by 10 to 20 percent in 2008 in Spain, according to a study last year by the National Association for the Control of Plagues (ANECPLA).

The worst-hit regions are in the Canary Islands and along the Mediterranean coast, both tourist destinations, the study said.

It said that the hotel sector has been particularly badly hit. Four- and five-star establishments appear to have been the worst hit, but that may be because their system for detecting the insects is more advanced.

In its manual, the Madrid regional government advises hotels on how to train employees to detect the pests.