Malaria-endemic countries should increase vigilance
National monitoring essential step in preventing the emergence of malaria drug resistance
18 NOVEMBER 2010 | GENEVA -- WHO is calling on countries to be increasingly vigilant in monitoring antimalarial drug efficacy in order to allow for early detection of artemisinin resistance.1 This is one among several conclusions of the Global report on antimalarial drug efficacy and drug resistance: 2000–2010, released today. The report is based on 1100 studies conducted by national malaria control programs and research institutes over the ten-year period.
The report estimates that only 34% of malaria-endemic countries are complying with WHO recommendations to routinely monitor the efficacy of first- and second-line antimalarial medicines.2
Global report on antimalarial efficacy and drug resistance: 2000-2010
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"A greater political commitment to support and sustain national monitoring of the efficacy of antimalarial medicines is critical to prevent a wider emergence of artemisinin resistance", said Dr Pascal Ringwald of the Drug Resistance and Containment Unit, within WHO's Global Malaria Programme and one of the report authors.
Resistance to artemisinin
In February 2009, WHO confirmed that resistance to artemisinin had emerged on the Cambodia-Thailand border. Although patients infected were cured following treatment with an artemisinin-based combination therapy (ACT), the recovery took more time. In artemisinin-resistant areas, the high cure rates observed depend heavily on the efficacy of the non-artemisinin component of the combination.
Nonetheless, the report found that ACTs currently recommended by national malaria control programmes remain efficacious in treating malaria, with cure rates generally greater than 90%. In countries where the currently recommended ACT has a cure rate of less than 90%, policy change is ongoing to implement an efficacious replacement treatments for malaria.
"The emergence of artemisinin resistance on the Cambodia-Thailand border has been a wake-up call to the world to prevent its spread, increase monitoring, and preserve ACTs as the only effective treatment we have for falciparum malaria", said Dr Robert Newman, Director of WHO's Global Malaria Programme. "Prompt action will be critical to sustain progress in malaria control and achieve the health-related Millennium Development Goals."
Containing the spread of artemisinin resistance
Efforts to contain the spread of artemisinin resistance on the Cambodia-Thailand border have been ongoing since November 2008. However, there is some early evidence that resistance to artemisinins may also be emerging on the Myanmar-Thailand border. There is also concern that resistance could spread from the Cambodia-Thailand border to Africa, as it did with antimalarial drugs such as chloroquine and sulfadoxine-pyrimethamine in the 1960s and 1970s.
"Antimalarial drug resistance is like a cancer, it must be fought at every level – affected countries need to be in the frontline in combating the emergence of drug resistance. WHO should be empowered and supported to take a strong lead. It is crucial to protect ACTs as they are the best treatments for millions of people against malaria," said Professor Nicholas J White, of the Mahidol-Oxford Research Unit in Bangkok, Thailand.
Since 1973, WHO has been providing support to national malaria control programmes to monitor drug resistance by regularly updating the standardized therapeutic efficacy study protocol, supporting and coordinating the collection, analysis and reporting of data, and promoting appropriate use of additional tests needed to confirm resistance.
Why artemisinin resistance occurs
Scientists continue to investigate how and why artemisinin resistance specifically emerges. Generally, antimalarial drug resistance first emerges through a rare spontaneous change in the malaria parasite. The subsequent ability of the drug resistant strain to survive and spread is influenced by many factors, including the use of substandard medicines and artemisinin-based monotherapies. However, it is clear that if the efficacy of artemisinin component continues to decline, there is an increased risk that resistance to non-artemisinin medicines used in the combination will emerge. Currently, research efforts are ongoing to discover and develop new medicines for the treatment of malaria.
In response to the findings in this report, WHO is working with partners to develop a Global Plan for Artemisinin Resistance Containment, which will be released in January 2011. On World Health Day 2011, WHO will launch a public awareness campaign on antimicrobial resistance and its global spread, calling on governments and stakeholders to implement the policies and practices needed to safeguard medicines for future generations.