Drug-resistant malaria infections are now widespread in Southeast Asia and pose a global health risk, according to a study just published in the New England Journal of Medicine.
The researchers found the deadliest form of the malaria-causing parasite, P. falciparum, has developed resistance to the most effective anti-malarial drug, artemisinin. The drug-resistant parasite is firmly established in northwestern Cambodia, Thailand, Vietnam, and eastern Myanmar. They also found signs of emerging resistance in central Myanmar, southern Laos and northeastern Cambodia.
The spread of resistance to artemisinin—and an emerging resistance to the partner drugs used in combination with it—may reverse the substantial recent gains made in malaria control, the researchers said.
Malaria is spread when an infected person is bitten by a female mosquito of the genus Anopheles and the mosquito bites another person. When a patient has a drug-resistant form of the parasite, treatment takes longer and provides more opportunity for transmitting the infection to greater numbers of mosquitoes. And the Anopheles mosquito is showing resistance to all classes of insecticides in 64 countries where malaria is prevalent, posing yet another risk of increasing rates of malaria and death according to the World Health Organization (WHO).
Researchers did not find the drug-resistant malaria parasites in the three African sites included in the study: Kenya, Nigeria, and the Democratic Republic of Congo. Still, they fear the parasite could eventually spread across Asia and into India and Africa. If that happens, the global consequences could be dire because no alternative anti-malarial medicine is available with the same level of efficacy and tolerability as artemisinin and its partner drugs.
Nicholas White, the study’s senior author, believes “conventional malaria control approaches won’t be enough” to stop this new problem, according to Wellcome Trust. “We will need to take more radical action and make this a global public health priority, without delay.”
To date there is no preventative vaccine against malaria. Controlling the disease relies heavily on the use of anti-malarial drugs that kill the parasite after it infects a human body. Drug-resistant mutations are not new. Every time a new anti-malarial drug has been developed, the parasites have acquired a resistance to it. In the early 1950s, Chloroquine (CQ) was the most widely used drug but P. falciparum became resistant to it after about 10 years. The CQ-resistant parasite appeared first in Colombia and Thailand but quickly spread through most endemic areas. CQ was replaced with a combination of two drugs, Sulfadoxine-pyrimethamine (SP) but resistance developed rapidly.
In the past decade, the use of artemisinin has been extremely effective in the fight to control malaria. According to the Tracking Resistance to Artemisinin Collaboration,the global malaria mortality rate was reduced by 45 percent between 2000 and 2012.
About 3.4 billion people, half of the world’s population, are at risk of contracting malaria. The disease took an estimated 627,000 lives in 2012, mostly children under five years of age in Africa, according to Margaret Chan, WHO director-general.