WINNIPEG - Bed bugs are no longer just the stuff of bedtime rhymes with the blood-sucking critters increasingly becoming a problem in large Canadian cities.

They are hitching rides with international travellers and moving from home to home in used furniture, creating problems in bedrooms from coast to coast.

"We're all experiencing an increase in the incidences of bed bugs," said Reg Ayre, manager of the healthy environments program with the Toronto public health department.

"We're seeing it right across the board whether you are in (a) very elite area, in a single family residence, whether you are in a five-star hotel or whether you are in the local rooming house down on the corner. We're seeing it all over the place."

The wingless insects invade mattresses, curtains or tiny crevasses in the wall, coming out to feast on humans while they sleep.

Bed bugs used to be fairly common around the time of the Second World War, Ayre said. As harsh pesticides like DDT gained popularity, he said the bed bug population dipped along with the population of other household pests, such as cockroaches and ants.

But with the phase-out of such harmful pesticides, Ayre said bed bugs are making a comeback.

"Folks have lost the knowledge on how to deal with bed bugs," he said.

There are several theories about why bed bugs are thriving in North America once again, said University of Manitoba entomologist Terry Galloway.

Some blame international travel, arguing bed bugs are stowing away in clothes and suitcases to set up homes in Canadian bedrooms.

But Galloway said bed bugs are also capable of covering large enough distances on foot, travelling from apartment to apartment quickly within a building.

Used furniture is also a good way to spread the bugs, he said.

When they find a warm place close to a source of food, Galloway said they start to reproduce relatively quickly.

While bed bugs aren't known to spread infectious disease, Galloway said some people develop welts after being bitten.

Still, he said many people -- even entomology students -- don't recognize the telltale signs of bed bugs such as clusters of bites and small droppings on the sheets. Even when bed bugs are identified, he said some people are often ashamed.

"They've often been associated with poverty," said Galloway. "That's not necessarily true at all. It's the same as head lice. Anybody can get head lice. It doesn't have anything to do with social status or anything else."

Several years ago, Winnipeg exterminator Lincoln Poulin said he'd get one or two calls a year about bed bugs. These days, his Western Canada pest control chain gets an average of 10 calls a day.

"These insects are literally everywhere," he said. "I've treated moving vans for them."

Bed bugs are hearty creatures, living up to a year without food in cold climates, which makes them tough to get rid of, Poulin said. You can't just close off a room or shut down a summer camp and expect them to die off on their own, he said.

The longer the bugs live in your bedroom, the harder it is to get rid of them, Poulin said. Washing clothes right away after returning from a trip and vacuuming out the suitcase can help kill bed bugs before they settle in, but Poulin said very few people tend to do that.

"Bed bugs are so tiny, people have a hard time seeing them," he said. "They bring them home and they don't even realize it."

Public health experts recommend regularly washing bedding and vacuuming mattresses to prevent infestations. They also recommend caution when buying used furniture. After returning from a trip, luggage should be kept in an isolated area of the home. All clothing in the suitcase should also be washed in the hottest water possible and put in a hot dryer for 20 minutes.