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Credit: James Gathany
Drug-resistant malaria parasites have spread to critical border regions of Southeast Asia, according to a study published in The New England Journal of Medicine.
The study confirms that resistance to the world’s most effective antimalarial drug, artemisinin, is now widespread in Southeast Asia.
This is not the first time malaria parasites have developed resistance to front-line drugs, and, each time, resistance has emerged from the same corner of Asia on the Cambodia-Thailand border.
To assess the extent of artemisinin resistance, researchers analyzed blood samples from 1241 malaria patients in 10 countries across Asia and Africa.
This revealed that artemisinin resistance in Plasmodium falciparum is now firmly established in western Cambodia, Thailand, Vietnam, eastern Myanmar, and northern Cambodia. There are also signs of emerging resistance in central Myanmar, southern Laos, and northeastern Cambodia.
There are no signs of resistance in the 3 African sites included in the study, located in Kenya, Nigeria, and the Democratic Republic of the Congo.
The study also suggested that extending the course of antimalarial treatment in areas with established resistance—for 6 days rather than the standard 3 days—could offer a temporary solution to this worsening problem.
“It may still be possible to prevent the spread of artemisinin-resistant malaria parasites across Asia and then to Africa by eliminating them, but that window of opportunity is closing fast,” said study author Nicholas White, FRS, of the University of Oxford in the UK.
“Conventional malaria control approaches won’t be enough. We will need to take more radical action and make this a global public health priority, without delay.”
He and his colleagues conducted this study by analyzing malaria-infected adults and children at 15 trial sites in 10 malaria-endemic countries between May 2011 and April 2013.
Patients received a 6-day antimalarial treatment—3 days of an artemisinin derivative and a 3-day course of artemisinin combination treatment (ACT). Then, the researchers analyzed patients’ blood to determine the rate at which the parasites were cleared.
The median parasite clearance half-life ranged from 1.8 hours in the Democratic Republic of the Congo to 7 hours at the Thailand-Cambodia border, where artemisinin resistance has been known to exist since 2005.
The proportion of patients with parasites in their blood 72 hours after treatment, a widely used test for artemisinin resistance, ranged from 0% in Kenya to 68% in Eastern Thailand.
Malaria infections that were slow to clear were strongly associated with a single point mutation in a P falciparum gene called kelch 13, an important validation of the recently discovered genetic marker (k13) in the DNA of the malaria parasite.
The researchers also found that patients who had slow-clearing infections were more likely to have parasite stages that can infect mosquitoes. This suggests artemisinin-resistant P falciparum parasites have a transmission advantage over parasites that are not resistant, which drives their spread.
“Frontline ACTs are still very effective at curing the majority of patients, but we need to be vigilant, as cure rates have fallen in areas where artemisinin resistance is established,” said study author Elizabeth Ashley, MBBS, PhD, also of the University of Oxford.
“Action is needed to prevent the spread of resistance from Myanmar into neighboring Bangladesh and India. The artemisinin drugs are arguably the best antimalarials we have ever had. We need to conserve them in areas where they are still working well.” 
Credit: James Gathany
Drug-resistant malaria parasites have spread to critical border regions of Southeast Asia, according to a study published in The New England Journal of Medicine.
The study confirms that resistance to the world’s most effective antimalarial drug, artemisinin, is now widespread in Southeast Asia.
This is not the first time malaria parasites have developed resistance to front-line drugs, and, each time, resistance has emerged from the same corner of Asia on the Cambodia-Thailand border.
To assess the extent of artemisinin resistance, researchers analyzed blood samples from 1241 malaria patients in 10 countries across Asia and Africa.
This revealed that artemisinin resistance in Plasmodium falciparum is now firmly established in western Cambodia, Thailand, Vietnam, eastern Myanmar, and northern Cambodia. There are also signs of emerging resistance in central Myanmar, southern Laos, and northeastern Cambodia.
There are no signs of resistance in the 3 African sites included in the study, located in Kenya, Nigeria, and the Democratic Republic of the Congo.
The study also suggested that extending the course of antimalarial treatment in areas with established resistance—for 6 days rather than the standard 3 days—could offer a temporary solution to this worsening problem.
“It may still be possible to prevent the spread of artemisinin-resistant malaria parasites across Asia and then to Africa by eliminating them, but that window of opportunity is closing fast,” said study author Nicholas White, FRS, of the University of Oxford in the UK.
“Conventional malaria control approaches won’t be enough. We will need to take more radical action and make this a global public health priority, without delay.”
He and his colleagues conducted this study by analyzing malaria-infected adults and children at 15 trial sites in 10 malaria-endemic countries between May 2011 and April 2013.
Patients received a 6-day antimalarial treatment—3 days of an artemisinin derivative and a 3-day course of artemisinin combination treatment (ACT). Then, the researchers analyzed patients’ blood to determine the rate at which the parasites were cleared.
The median parasite clearance half-life ranged from 1.8 hours in the Democratic Republic of the Congo to 7 hours at the Thailand-Cambodia border, where artemisinin resistance has been known to exist since 2005.
The proportion of patients with parasites in their blood 72 hours after treatment, a widely used test for artemisinin resistance, ranged from 0% in Kenya to 68% in Eastern Thailand.
Malaria infections that were slow to clear were strongly associated with a single point mutation in a P falciparum gene called kelch 13, an important validation of the recently discovered genetic marker (k13) in the DNA of the malaria parasite.
The researchers also found that patients who had slow-clearing infections were more likely to have parasite stages that can infect mosquitoes. This suggests artemisinin-resistant P falciparum parasites have a transmission advantage over parasites that are not resistant, which drives their spread.
“Frontline ACTs are still very effective at curing the majority of patients, but we need to be vigilant, as cure rates have fallen in areas where artemisinin resistance is established,” said study author Elizabeth Ashley, MBBS, PhD, also of the University of Oxford.
“Action is needed to prevent the spread of resistance from Myanmar into neighboring Bangladesh and India. The artemisinin drugs are arguably the best antimalarials we have ever had. We need to conserve them in areas where they are still working well.”
Credit: James Gathany
Drug-resistant malaria parasites have spread to critical border regions of Southeast Asia, according to a study published in The New England Journal of Medicine.
The study confirms that resistance to the world’s most effective antimalarial drug, artemisinin, is now widespread in Southeast Asia.
This is not the first time malaria parasites have developed resistance to front-line drugs, and, each time, resistance has emerged from the same corner of Asia on the Cambodia-Thailand border.
To assess the extent of artemisinin resistance, researchers analyzed blood samples from 1241 malaria patients in 10 countries across Asia and Africa.
This revealed that artemisinin resistance in Plasmodium falciparum is now firmly established in western Cambodia, Thailand, Vietnam, eastern Myanmar, and northern Cambodia. There are also signs of emerging resistance in central Myanmar, southern Laos, and northeastern Cambodia.
There are no signs of resistance in the 3 African sites included in the study, located in Kenya, Nigeria, and the Democratic Republic of the Congo.
The study also suggested that extending the course of antimalarial treatment in areas with established resistance—for 6 days rather than the standard 3 days—could offer a temporary solution to this worsening problem.
“It may still be possible to prevent the spread of artemisinin-resistant malaria parasites across Asia and then to Africa by eliminating them, but that window of opportunity is closing fast,” said study author Nicholas White, FRS, of the University of Oxford in the UK.
“Conventional malaria control approaches won’t be enough. We will need to take more radical action and make this a global public health priority, without delay.”
He and his colleagues conducted this study by analyzing malaria-infected adults and children at 15 trial sites in 10 malaria-endemic countries between May 2011 and April 2013.
Patients received a 6-day antimalarial treatment—3 days of an artemisinin derivative and a 3-day course of artemisinin combination treatment (ACT). Then, the researchers analyzed patients’ blood to determine the rate at which the parasites were cleared.
The median parasite clearance half-life ranged from 1.8 hours in the Democratic Republic of the Congo to 7 hours at the Thailand-Cambodia border, where artemisinin resistance has been known to exist since 2005.
The proportion of patients with parasites in their blood 72 hours after treatment, a widely used test for artemisinin resistance, ranged from 0% in Kenya to 68% in Eastern Thailand.
Malaria infections that were slow to clear were strongly associated with a single point mutation in a P falciparum gene called kelch 13, an important validation of the recently discovered genetic marker (k13) in the DNA of the malaria parasite.
The researchers also found that patients who had slow-clearing infections were more likely to have parasite stages that can infect mosquitoes. This suggests artemisinin-resistant P falciparum parasites have a transmission advantage over parasites that are not resistant, which drives their spread.
“Frontline ACTs are still very effective at curing the majority of patients, but we need to be vigilant, as cure rates have fallen in areas where artemisinin resistance is established,” said study author Elizabeth Ashley, MBBS, PhD, also of the University of Oxford.
“Action is needed to prevent the spread of resistance from Myanmar into neighboring Bangladesh and India. The artemisinin drugs are arguably the best antimalarials we have ever had. We need to conserve them in areas where they are still working well.”