Cambodia drug-resistant malaria stirs health fears

Sat Mar 6, 2010
Thin Lei Win

PAILIN, Cambodia (Reuters) - In a dusty village near the Thai-Cambodia border, 24-year-old Oeur Samoeun sits on a dark green hammock recovering from a strain of malaria that has resisted the most powerful drugs available.

Ravaged by days of fever and chills, he is considered lucky: the parasite has left his body. But for many others, the potentially deadly disease never quite disappears.

His province of Pailin is the epicenter of strains of malaria that have baffled healthcare experts worldwide, raising fears a dangerous new form of malaria could already be spreading across the globe.

"The fear is what we're observing right now could be the starting point for something worse regionally and globally," said Dr. Charles Delacollette, Mekong Malaria Program Coordinator at the World Health Organization.

A New England Journal of Medicine study last year showed that conventional malaria-fighting treatments derived from artemisinin took almost twice as long to clear the parasites that cause the disease in patients in Pailin and others in northwestern Thailand, suggesting the drugs were losing potency in the area.

That is echoed by U.S. development agency USAID, which says artemisinin-based combination therapy is "now taking two to three times longer to kill malaria parasites along the Thai-Cambodian border than elsewhere." The agency has helped to monitor the situation in the area for years.

The disease transmitted via mosquito bites kills more than 1 million people worldwide each year and children account for about 90 percent of the deaths in the worst affected areas of sub-Saharan Africa and parts of Asia.

The studies shine a spotlight on the remote province of Pailin, a former stronghold of ultra-communist Khmer Rogue rebels and once renown for blood-red rubies and lush forests.

MULTIPLIED AND DISPERSED

Pailin is the origin of three drug-resistant malaria parasites over the past five decades. Thanks to prolonged civil conflict, dense jungles and movement of mass migrants in the gem mines in the 1980s and 90s, the strains multiplied and dispersed through Myanmar, India and two eventually reached Africa.

Few can say why it is a hotbed for drug-resistant malaria but experts point to a combination of sociological factors and a complicated history spanning the Khmer Rouge era when 1.7 million people, nearly a quarter of Cambodia's population, perished from execution, overwork or torture during their 1975-79 rule.

Driven from the capital, the rebels waged an insurgency from western Cambodia with Pailin one of their last holdouts until their defeat in the late 1990s.

"During the Khmer Rouge era, people came here illegally and when they get malaria, they go to the market, buy pills and self-medicate," Sophal Uth, a Pailin-based field officer for non-profit Malaria Consortium said. "It was difficult for the government to control."

With weak public health infrastructure and rising malaria cases, Cambodia made malaria drugs available over the counter more than a decade ago. Most Cambodians don't have access to public health services and rely on private medical centers.

The strategy carried risks. Easy access reduced the number of cases but also led to incorrect dosages and substandard or counterfeit medicine, which instead of killing the parasites only make them stronger.

For some like Oeur, a migrant worker who likely caught malaria on a logging trip or while sleeping in his rickety shed without a mosquito net, artemisinin-based medicine still works.

Artemisinin, derived from the sweet wormwood, or Artemisia annual plant, is the best drug available against malaria, especially when used in artemisinin combination therapy (ACT) medicines made by firms such as Swiss drugmaker Novartis AG and France's Sanofi-Aventis.

MOST HAVE HAD MALARIA

After three days of ACT, Oeur is weak but parasite-free.

The Mekong River region of Thailand, Cambodia, Vietnam and Laos use ACTs against the "falciparum" parasite, the most severe form of malaria, as suggested by the World Health Organization.

"Artemisinin is the most effective antimalarial we have left," Dr. Chansuda Wongsrichanalai of USAID's office of public health in Bangkok said. "We don't have any ideal alternatives available and ready to for use in a control programme right now."

Pailin's gem mines are gone and so are most foreign migrants and the troops. Severe deforestation has left most hill tops barren. Yet the parasites are as virulent as ever. Most of its inhabitants have had malaria at least once in their lives.

Malaria experts, weary of being called alarmists, are quick to point out ACTs still work -- they are just taking longer. The WHO isn't even calling it drug-resistance, they preferred to use the term "altered response" or "tolerance to artemisinin."

"From a public health perspective, I don't think it really matters much if it's resistance or something else given that at the end of the month, patients are returning to the health facility with the same malaria," Dr. John MacArthur, chief of the President's Malaria Initiative at the U.S. Centers for Disease Control and Prevention said.

Potential fallout from ACT resistance led the Bill & Melinda Gates Foundation to fund a $22.5 million containment programme. Cambodia will also receive $102 million from The Global Fund to fight malaria in the next five years.

The Gates Foundation programme aims to use screening, bed nets and grass-roots muscle to contain the parasites along the border area and eliminate them before they can spread further.

Last November, Malaria Consortium said studies show artemisinin resistance already may be present in Myanmar, China and Vietnam, where between 12-31 percent of patients still had the parasite in the system after three days of treatment.

(Editing by Jason Szep and Bill Tarrant)