Sitting in a cluttered yard behind a series of wooden shacks, chickens pecking in the dust all around, Meoun Naem waits to be given a second dose of drugs. He's sweating and the whites of his eyes have a yellow hue, a legacy of earlier bouts of malaria; Meoun Naem estimates that this is the 10th time he has contracted the disease.
The 30-year-old has recently been diagnosed with Plasmodium falciparum, the deadliest strain of malaria. He's weak and has been unable to work for several days.
"It started with a high fever, muscle and joint pain and continued from there," he says.
He hitched a ride from the farm on which he earns US$5 a day as a seasonal worker to the village of Salakhoa, close to the Cambodian-Thai border. He came to get tested and, as it proved necessary, treated by a member of the Village Malaria Workers, a network of trained volunteers set up over the past few years to combat one of the biggest threats to surface in recent decades in the global fight against the disease.
In December 2008, researchers published a letter in the New England Journal of Medicine (NEJM) based on a study conducted on malaria patients in the west of Cambodia. The study showed evidence that malaria parasites in the area were developing resistance to artemisinin, which, when combined with other anti-malarial drugs, has formed one of the few effective treatments against Plasmodium falciparum.
While the news was a major setback in the fight against malaria, the source of this new threat wasn't exactly a surprise; since the 1970s, western Cambodia's Pailin province, a poor, agricultural area that is still recovering from decades of brutal Khmer Rouge rule, has held the ominous distinction of being ground zero for new drug-resistant malaria strains.
"In the past 50 years, this Thai-Cambodian border area has been the very birthplace of all drug resistance," says Steven Bjorge, speaking late last year, before he retired as team leader of the malaria and vector-borne diseases department of the World Health Organisation in Cambodia. "Every drug that has replaced previous drugs has become resistant first in this area before becoming resistant elsewhere."
THE MAIN STREET IN the town of Pailin is a two-lane road lined with simple shacks serving as stores and restaurants. Small dirt roads intersect it, but the heart of the town can be driven through in a matter of minutes.
The province was once known for its gem trade, but in recent years the size and number of precious stones found has dwindled, though locals still search the rivers after heavy rainfall and swap stories about other people's life-altering finds. Stalls at the town's central market, where gems are still sometimes traded, sell basic agricultural supplies and food, and are surrounded by muddy puddles and potholes streaked with oil.
The few four-wheel-drive vehicles in town generally bear the logo of one of the international NGOs operating in the region (most of them focused on malaria prevention and de-mining).
Situated down one of the town's dirt roads, the Cambodian Red Cross' local office - a wooden shack - is deserted in the afternoon heat, although the door is wide open.
Down another muddy side road, in the small Malaria Consortium office, instances in which malaria cases have shown resistance to artemisinin-based medicines have been plotted on a map on the wall. There have already been confirmed cases in Cambodia and across the border in Thailand, and a recently added postscript pinned to the map refers to cases that have been reported in Myanmar and China.
"Our big concern is the spreading of resistance from one country to another, one region to another," says Sophal Uth, the map hanging behind him. The Cambodian doctor has been working on containment in the region since 2009 and is the field office co-ordinator for the non-profit Malaria Consortium's in Pailin.
Malaria has been a deadly threat throughout human history and, every year, hundreds of millions still fall sick as a result of the mosquito-borne parasite - most of them in Africa, where it is estimated that a child dies from the disease every minute. There were an estimated 627,000 malaria-related deaths in 2012, the majority caused by Plasmodium falciparum, and according to the WHO, one-fifth of the world's population still live in areas where there is a high risk of infection.
Meanwhile, all but four countries in the world use artemisinin combination therapy (artemisinin plus one other drug) as their first-line treatment for Plasmodium falciparum.
"All we need is one or two artemisinin-resistant cases to cross into Thailand, Myanmar and then onwards. Our big concern is how we can contain this," Sophal Uth says, his desk surrounded by piles of insecticide-treated bednets and educational material.
Since 2008, tens of millions of dollars have been spent in Cambodia by major organisations such as the Global Fund to Fight Aids, Tuberculosis and Malaria, the WHO and the Bill & Melinda Gates Foundation to stop the potentially devastating spread of artemisinin-resistant malaria, as well as on attempting to eradicate the disease once and for all.
A containment project was quickly put into place soon after the NEJM letter was published, with bednets liberally distributed across the province. "We achieved full bednet coverage in 2009," says Bjorge. Education programmes and call-in radio shows were set up and free malaria testing and treatment were offered across the province. In cases where Plasmodium falciparum is found to be still present in a patient's body three days after treatment has begun, chemicals are sprayed in a 100-metre radius around their home in an attempt to kill off host mosquitoes.
Last April, the WHO launched an emergency response across the Greater Mekong subregion.
"The world is watching," said Shin Young-soo, WHO regional director for the Western Pacific, at its launch. "We cannot afford to fail."
Malarone, a stopgap drug, was used throughout Pailin and neighbouring Battambang province and proved highly successful. Malarone, however, wasn't a long-term replacement for artemisinin combination therapy.
"Malarone is not used in normal malaria areas," says Bjorge. "It is expensive - US$50 a dose - and with Malarone it only takes one point mutation - one mutation in one gene - for it to become resistant. So we don't want to use it for too long. The less we use it and the quicker we can transition to a new drug the better."
Across Cambodia, malaria-related deaths dropped 78 per cent in the first 10 months of 2013 from the same period the year before; down from 37 to eight. Overall malaria cases dropped from 59,668 to 33,769, due mainly to a reduction in breeding grounds, wider bednet coverage and better access to testing, treatment and drugs.
"The goal is no more malaria deaths in the region by 2015, and no more malaria by 2020," says Kaem Monykosal, deputy director at the main hospital in Pailin. "It is hard to predict if this is possible, but over the last three years we've achieved a lot."
OVER THE PAST FEW years, a network of hundreds of trained volunteers has been set up to conduct simple blood tests, refer bad cases to the hospital and administer anti-malarial drugs to those who test positive for the parasite. For their efforts, each Village Malaria Worker is paid about US$17 a month.
The goal is not simply to monitor drug-resistant malaria in the region but also to educate the population and attempt, through better habits and quicker treatment, to further reduce the number of malaria cases.
"The Village Malaria Workers, they are the key frontline people," says Sophal Uth, on a field trip to visit one such worker.
As our mud-splattered four-wheel drive arrives in her village, 28-year-old Hong Chheong Ly is waiting. She treats people out of the back of her family's store, a bag of medicine and documents on which to mark her findings always within easy reach.
"I've been doing this for about six months," she says. "Before, I didn't really understand how you get malaria, or how you recover from it."
Now she is able to test the blood of - and when necessary administer anti-malarial pills to - anyone within her 300-person community, as well as seasonal farm workers in the area.
As we talk, Reoum Phearom, a nervous 15-year-old, arrives. He came to Pailin recently with his older sister, to find crop-planting work. Now he is feeling sick and wants to get tested for malaria.
Hong Chheong Ly performs a simple blood test, pricking the tip of the boy's finger and placing a small drop of blood onto one of her rapid detection kits. Twenty minutes later the results come back: Reoum Phearom doesn't have Plasmodium falciparum nor Plasmodium vivax, the two strains of malaria most prevalent in the region.
After a relieved-looking Reoum Phearom answers some basic questions for Hong Chheong Ly's paperwork - the boy cannot read or write - Sophal Uth quizzes him about his habits. He admits that, despite having a mosquito net, he never sleeps under it, preferring instead to stay out in the open, in a hammock. It quickly becomes clear that Reoum Phearom has never been told that malaria is caught from mosquito bites.
"We are trying to educate people about mosquitoes causing malaria, but still some believe the old ways - that it comes from spirits in the forest," says Sophal Uth, after Reoum Phearom leaves. "In the past, these people went to traditional healers; some got better but most of them died. I've heard plenty of stories like this."
Sophal Uth is hopeful that the boy has gone away with a bit more knowledge about the causes of malaria.
Our drive back through the borderlands takes us past vibrant green fields, wooden shacks and several small, tented encampments, where seasonal workers live, often with their whole families sleeping under a single bednet.
WHEN THE KHMER ROUGE regime was brought to an abrupt end, in 1979 - after causing the deaths of an estimated two million people - its remaining forces and leadership retreated to the poorer mountainous regions in the north and west of the country. It wasn't until the late 90s, when the civil war officially ended, that Pailin returned to central government control.
"Since 1997 we have moved forwards," I'm told over lunch by H.E. Mey Maak, vice-governor of Pailin province, who, like many of the region's top politicians, had been a Khmer Rouge leader until the area's wholesale defection to the government side in 1996. "We have peace now but some sectors, like health care, we basically started from zero in the late-90s."
Legacies of that dark period are still present, however: in the fields, land mines dating from the 80s and 90s are a continual threat - during my three-day visit, a farmer is killed when his tractor drives over an unexploded mine.
In the past, poorer residents who suspected they had malaria often had little choice but to visit a pharmacist, buy a few anti-malarial pills and take them until they felt better. The makeshift nature of malaria treatment was hardly an effective means of controlling the disease and doctors believe that drug-resistance could have developed from years of fake medicines being sold here - medicines that often contained a small amount of the real drug; enough to offer improvements but not to completely remove the parasite. (A 2006 investigation of artemisinin-based anti-malarials across Southeast Asia found that roughly half the samples were fakes).
"Everything was so unregulated," says Sophal Uth.
At the same time, many sick people would take the medicine until they felt better and then stop, without finishing the course of treatment, or take anti-malarial medicine for a common cold or fever. This allowed malaria parasites to develop resistance to the drugs.
Since 2010, the sale of anti-malarial drugs in Pailin has been banned and anyone feeling sick must go to the hospital or one of the Village Malaria Workers for free testing and treatment. The medicine must now be swallowed in the presence of a doctor or volunteer, to ensure that the full course is completed.
One morning I accompany 57-year-old Nuth Tith as he makes his rounds. It is part of his job, as a drug inspector, to make sure no anti-malarial drugs are being sold and that the medicines legally on offer are genuine and within their expiration dates.
"In the past year we've found 17 kinds of fake or expired drugs for sale, but no anti-malarial drugs," Nuth Tith says, standing beside one of the dozen or so clinics that surround Pailin's central market. An anti-malaria instruction poster, bleached by the sun, decorates one of the walls.
The day before, Nuth Tith, who patrols the town in a smart blue uniform and peaked cap, conducted an undercover operation to see if any of the clinics would give anti-malarial drugs to a stranger; he is happy to report that they all refused, and simply referred the person to the malaria clinic at the hospital.
A 40-MINUTE DRIVE outside Pailin town, down heavily rutted roads, Seng Pin's farm almost straddles the border with Thailand. The 74-year-old farmer has 50 migrant workers in his employ at any one time, with some staying for a full season and others leaving after a few weeks or months.
Mosquito nets hang from the ceiling of a large barn, home to the labourers when they aren't in the fields harvesting corn. Children play in the yard, poking sticks at a fattened pig.
"In the past we would have about eight people every year who would get malaria," Seng Pin says, adding that there have been far fewer cases since they put the nets up three years ago.
The transitory nature of many of those working in Pailin province is of concern to those monitoring the malaria situation in the region. These are the people most likely to spread a resistant strain of malaria to different communities and across borders (the Anopheles mosquito, the carrier of malaria, only travels nine kilometres in its lifetime, so malaria relies on human carriers to spread it across large distances).
Once, Cambodian workers from Pailin would cross back and forth into Thailand to find work or to trade, helping to spread the disease. Myanmese miners would also come to Pailin, to mine for precious stones. Nowadays, the migration is more localised.
"There are no more Burmese gem miners, they've moved on. Times have changed," says Bjorge. "Factors that might have spread malaria 20 years ago don't exist anymore."
Even so, in September, Malaria Consortium began offering voluntary malaria testing at checkpoints between Thailand and Pailin province to try to identify and treat infected people before they could inadvertently spread drug-resistant Plasmodium falciparum.
Containment activities are also set to begin this year in Laos, where a recent trial found that 22.2 per cent of patients treated with artemether-lumefantrine (an artemisinin combination therapy) were still parasitic three days after treatment began.
"There is a chance we may be able to eliminate Plasmodium falciparum in the area in another couple of years," says Bjorge, but, he adds, this is unlikely to stop an eventual resistance forming to artemisinin elsewhere in the world. The best it can do is push the fight against malaria another step down the road. "We're seeing artemisinin-resistant cases appearing in South America. As far as I know there is no link to the Pailin area - it is just natural mutation."
"For the longest time, if people have heard about Pailin it is related to malaria," says Lim Kimseng, an officer for FHI 360, an NGO focusing on global health and development. "Maybe one day that will change."
Thanks to a great deal of effort by a number of concerned organisations, that day may indeed come.