Parasites want to survive, and that is bad news for humans.

By THOMAS FULLER

TASANH, Cambodia - The afflictions of this impoverished nation are on full display in its western corner: the girls for hire outside restaurants, the badly rutted dirt roads and the ubiquitous signs that warn“Danger Mines!”

But what eludes the naked eye is a potentially graver problem, especially for the outside world. The parasite that causes the deadliest form of malaria is showing the first signs of resistance to the best new drug against it.

Combination treatments using artemisinin, an antimalaria drug extracted from a plant used in traditional Chinese medicine, have been hailed in recent years as the biggest hope for eradicating malaria from Africa, where more than 2,000 children die from the disease each day.

Now a series of studies, including one recently published in The New England Journal of Medicine and one due out soon, have cemented a consensus among researchers that artemisinin is losing its potency here and that increased efforts are needed to prevent the drug-resistant malaria from leaving here and spreading across the globe.

“This is something we can’t just slide under the carpet,”said R. Timothy Ziemer, a retired admiral in the United States Navy who heads the President’s Malaria Initiative, the $1.2 billion program started by the Bush administration three years ago to cut malaria deaths in half in the countries affected worst.

Admiral Ziemer met with Thai and Cambodian officials in December to assess the resistance problem, which affects the same drugs used by the malaria initiative in Africa.

Malaria experts note that several times in the past, this same area around the Thai-Cambodian border appears to have been a starting point for drug-resistant strains of malaria, starting in the 1950s with the drug chloroquine.

Introduced immediately after World War II, chloroquine was considered a miracle cure against falciparum malaria, the deadliest type. But the parasite evolved, the resistant strains spread, and chloroquine is now considered virtually useless against falciparum malaria in many parts of the world, including sub-Saharan Africa.

It took decades for this resistance to spread across the world, so by the same token artemisinin-based drugs are almost sure to be useful for many years.

To protect against artemisinin resistance, the global health authorities are trying to assure that it is sold only as a combination pill with other antimalaria medicines that linger longer in the blood, mopping up any artemisinin-resistant parasites.

“This could spread in any direction; we have to make sure it doesn’t,”said Pascal Ringwald, malaria coordinator at the World Health Organization.“We know it’s not yet in Bangladesh,”he said.“It’s not yet in India.”

Artemisinin-based combinations turned out to be fast-acting and seemed to slow transmission of the disease, said Dr.John MacArthur, an infectious disease expert with the United States Agency for International Development in Bangkok.

Dr.MacArthur and others say resistance to malaria drugs is a natural consequence of widespread use of the drug.

“In the case of malaria, it’s the Darwinism of the parasite,”he said.“It likes to survive.”

Still, some researchers remain concerned about sending the wrong message to the public about the efficacy of artemisinin-based drugs.

“This is not the death knell of artemisinin,”said Dr.Nicholas White, a malaria expert who is chairman of a joint research program between Oxford University and Mahidol University in Thailand.“The drug still works in Cambodia, maybe not as well as before.”

But given the history of drug failures here, there appears to be a consensus on the solution.“Get rid of all malaria from Cambodia,” Dr.White said.“Eradicate it. Eliminate it.”