Reviled as vermin through the ages, rats are becoming unlikely soldiers in the struggle against two scourges of the developing world: land mines and tuberculosis.

In Mozambique, special squads of raccoon-size rats are sniffing out lethal explosive devices buried across the countryside, remnants of the country's anticolonial and civil wars of the last century.

In neighboring Tanzania, teams of rats use their twitchy noses to detect TB bacteria in saliva samples from four clinics serving slum neighborhoods. So far this year, the 25 rats trained for the pilot medical project have identified 300 cases of early-stage TB - infections missed by lab technicians with their microscopes. If not for the rodents, many of these victims would have died and others would have spread the disease.

"It's fair, I think, to call these animals 'hero rats,' " said Bart Weetjens, the Belgian conceiver of both programs.

The rat squads, at first derided by some interna tional aid officials as ridiculous, have won support from the World Bank and praise from the UN and land mine eradication groups. Now there are plans to deploy the creatures to Angola, Congo, Zambia, and other land mine-infested lands.

The rats' "noses are far more sensitive than all current mechanical vapor detectors," Havard Bach, a mine-clearing specialist with the Geneva International Center for Humanitarian Demining, wrote in a study.

Although rats make almost everyone's short list of horrors - associated with filth, disease, and destruction of food crops - they "are really nice creatures," according to Weetjens.

"They are organized, sensitive, sociable, and smart," said the former product engineer in a telephone interview from Antwerp, Belgium, home base for Apopo International, the nonprofit organization that trains and deploys the rats.

In the 1990s, he journeyed to Africa to study land mine clearance techniques. He put his engineer's mind to the expensive, clumsy, and often risky methods employed to detect the lethal contraptions of metal and explosive that detonate underfoot.

Land mines claim casualties for decades after the last shot is fired in a conflict; millions are strewn in former and present fighting zones across Africa, Asia, and Europe. The wickedly durable antipersonnel devices kill or maim thousands of people every year, mainly in the poorest of countries. Removal of the weapons is a priority of the United Nations and other groups.

"In Africa, it came to me: Rats can be part of this great effort," Weetjens recalled.

So he started training giant pouched rats - an African species known for its large size, sunny disposition, and ultra-keen nostrils - to detect the faintest whiff of TNT and other explosives. Because the rats are too light to trigger the explosive, they are not harmed in the exercise; they simply signal the location of the explosive to a handler, who has it defused and removed.