Malaria parasites in eastern Africa have developed resistance to artemisinins, essential first-line drugs used in combination therapies, jeopardizing the progress made in recent decades against the disease.
Treatment of nonsevere cases of malaria with a combination of artemisinins with a partner antimalarial has been used as an effective first-line therapy since the early 2000s, typically clearing malaria parasites from a patient’s blood within three days of treatment.
Resistance to artemisinins in the Plasmodium falciparum parasites causing malaria was first reported in Southeast Asia in 2009; reports of resistance to some partner drugs soon followed. The treatment failure rate in some parts of Southeast Asia reached 85% by 2016.
Resistance to artemisinins has been determined to be due to mutations in the P. falciparum gene Pfkelch13.
A team of researchers led by Didier Ménard, PhD, of the Université de Strasbourg/Institut Pasteur in Strasbourg, France, reported their findings from studies in Eritrea in a report published in the New England Journal of Medicine in which the team, along with colleagues from Eritrea’s Ministry of Health, assessed the effectiveness of artemisinin-based combination therapies in nearly 1,000 patients in Eritrea between 2016 and 2019.
The researchers found that while the drugs failed to clear parasites in only 0.4% of the Eritrean patients in 2016, that number rose to 4.2% by 2019, crossing the World Health Organization’s threshold for declaring resistance. Furthermore, by 2019, approximately 1 in 5 of the patients studied was infected with artemisinin-resistant parasites with the mutated Pfkelch13 gene.
How widespread the mutations in Pfkelch13 shown in the Eritrean cohort are in other parts of Africa remains to be seen. The researchers note in their report the emergence of partial resistance to artemisinin in Rwanda and Uganda. However, the researchers noted that approximately 17% of the Eritrean cases had P. falciparum with genetic deletions that render the parasite undetectable with a rapid diagnostic test which, while no longer in use in Eritrea, is still the most commonly used throughout Africa for malaria.
With 95% of malaria deaths occurring in Africa, any increase in drug resistance on the continent is cause for alarm. The authors say that the emergence and spread of these resistant parasites “threaten to compromise regional malaria control and elimination campaigns.”