Molecular surveillance of antimalarial resistance in Mozambique

Chloroquine susceptibility is returning and markers of artemisinin resistance are absent, but piperaquine resistance may spread across the country if drug selection pressure increases. These are the results of a study performed in Mozambique and led by ISGlobal, an institution supported by “la Caixa” Foundation, and published in Emerging Infectious Diseases.

Antimalarial drugs play a key role in malaria control. However, their efficacy can be affected by the emergence of drug-resistant parasites (Plasmodium falciparum). Indeed, over the last decades, scientists have described several gene mutations that confer resistance to almost all antimalarial drugs, including chloroquine, mefloquine, lumefantrine and piperaquine. Worryingly, strains resistant to artemisinin- one of the first-line treatments- have been reported in Southeast Asia.

“Drug resistance caused by genetic variations is a phenomenal art where the malaria parasite is the artist with 24 million shades on its color palette”, says Himanshu Gupta, first author of the study.

To maintain drug efficacy, several countries including Mozambique have changed their antimalarial drug policies, passing from chloroquine to amodiaquine, sulphadoxine-pyrimethamine (SP) to artemisinin-based combination therapies such as arthemeter-lumefantrine (AL).

Molecular markers of resistance to antimalarial drugs are a powerful tool to confirm the presence of resistant strains and explain drug failure. In this molecular surveillance study, the authors analyzed DNA from a total of 351 parasites isolated from children with malaria in different study regions of Mozambique. Specifically, they looked for mutations (in the K13, pfcrt, pfmdr1, pfdhps genes) and amplifications (in pfpm2 and pfmdr1 genes) associated with resistance.

The results show a high prevalence of SP resistance, likely due to its constant use as preventive treatment in pregnancy. They also indicate the low presence of parasites with multiple copies of pfpm2 circulating in Southern Mozambique, suggesting piperaquine resistance may spread to the rest of the country if drug pressure increases. In contrast, susceptibility to chloroquine is returning in most regions, and no markers of artemisinin resistance were found.

“These baseline prevalence data will allow us to determine the impact of malaria control or elimination programmes, such as mass drug administration, on resistance evolution” says Alfredo Mayor, ISGlobal researcher and study coordinator.