WHO report reviews 10 years of anti-malarial drug resistance

Because of the small amount of available treatments, anti-malarial drug resistance is a significant threat.

Newly elected Director-General of the World Health Organization (WHO) Tedros Adhanom Ghebreyesus attends a news conference at the United Nations in Geneva, Switzerland (photo credit: REUTERS)
Newly elected Director-General of the World Health Organization (WHO) Tedros Adhanom Ghebreyesus attends a news conference at the United Nations in Geneva, Switzerland
(photo credit: REUTERS)
The World Health Organization released a new report summarizing WHO surveillance of antimalarial-drug resistance from 2010 to 2019.
There are currently only a small number of drugs in use to treat malaria, a deadly disease which 1.1 billion people are at high risk of contracting and from which a child dies every two minutes, according to the WHO. Because of the small amount of available treatments, the importance of maintaining the efficacy of these drugs is vital and drug resistance is a significant threat.
The report found that first- and second-line artemisinin-based combination therapies (ACTs) remain effective overall in curing P. falciparum malaria, the malaria parasite responsible for 97% of global malaria deaths, and that all strains of this species of malaria can still be treated with at least two different ACTs.
There was "cause for concern" from findings in Rwanda and Guyana. In the latter, validated molecular marker C580Y associated with partial ACT resistance was reported in 2010 and 2017. In Rwanda, there was an increase in the prevalence of validated marker R561H of artemisinin partial resistance in 2018. To date, ACTs are still effective in both countries.
Where the WHO found that treatment efficacy was below 90%, treatment policy changes were made, according to the report.
High treatment failure rates were detected in Cambodia, Laos, Thailand and Vietnam. There were at least two ACT options available to effectively treat P. falciparum malaria in all of these countries.
Efficacy rates of the two ACTs most commonly used in Africa, the continent with the heaviest malaria burden in the world, were consistently high.
IT IS POSSIBLE that drug resistant strains of malaria can spread, but they are more likely to emerge independently, according to the WHO.
“Countries in the Greater Mekong are winning the battle against P. falciparum malaria. The massive reductions in disease and death reported across the sub-region in recent years are a testament to the sustained progress that has been achieved along the path toward elimination," said WHO Global Malaria Program Director Dr. Pedro Alonso.
"The threat of antimalarial drug resistance expanding from the Greater Mekong to other malaria-affected areas has been significantly reduced. What was once seen as the greatest challenge to malaria control globally has been brought under control. Countries still need to walk the last mile, but there is room for optimism,” he went on to say.
The report focused on ACTs, drugs made from artemisia annua, also known as the sweet wormwood plant, and a partner drug. In ACTs, the artemisinin compound reduces parasites in the first days of treatment while the partner drug eliminates the remaining parasites.
Artemisnin resistance generally means delayed clearance of parasites from the blood of those with malaria, meaning the ACT as a whole is less effective in treating the disease. Because the parasite's mechanisms of resistance against the artemisinin compounds affect only the ring stage of the malaria parasite cycle, the delayed clearance is categorized as partial resistance as opposed to drug resistance.
The report used therapeutics efficacy studies completed at regular intervals in the same location, with molecular markers for precise mapping, which enabled the WHO to detect declines in drug efficacy early.
There is currently no evidence that artemisinin partial resistance alone has resulted in an increase in malaria cases and deaths. Nearly all patients treated with an ACT along with an effective partner drug are fully cured, according to the WHO.
Multiple factors contribute to partial ACT resistance including "poor treatment practices, inadequate patient adherence to prescribed antimalarial regimens, and the widespread availability of oral artemisinin-based monotherapies and substandard forms of the drug," said the WHO.
Report data was collected from over 1,000 efficacy studies and molecular marker studies for P. falciparum drug resistance. The WHO global database has data from 66,000 patients worldwide.
Artemisinin resistance was first reported in the Greater Mekong sub-region (GMS) in 2008. Since then, there has been a decline in malaria deaths and cases.
The main risk factors for malaria death in these regions are insufficient access to a timely diagnosis and treatment rather than drug resistance, according to the WHO.