Resistance to malaria drugs in Africa may begin to take hold, according to a study that maps changes such as those seen a decade ago when drug resistance spread in Southeast Asia.
In Cambodia and neighboring countries, the artemisinin drugs widely used against malaria are no longer always effective. The falciparum malaria parasites have developed genetic mutations that allow them to evade drugs. There is great concern that drug resistance could spread to Africa, which has the largest number of cases of this type of malaria – and the highest number of deaths due to children.
A study in Rwanda, published Wednesday in the journal Lancet Infectious Diseases, shows that the dreaded erosion of the effectiveness of malaria medicine may have begun. As has happened in Southeast Asia, researchers have found that giving a course of medicine to artemisinin compound children does not always remove the malaria parasites from their blood within three days, as it should.
Artemisinins, introduced from China in the early 2000s, are given in combination with another type of malaria medicine to ensure that all parasites are cleaned and that the effectiveness of the drugs is not compromised. The most common combination is artemether lumefantrine, which Rwanda started using in 2006.
If the artemisinin does not clear the parasites quickly within three days, the partner drug comes under pressure and may develop resistance to it. At that point, treatment may fail, as has happened in Southeast Asia.
‘Mutations can occur spontaneously, and previous studies have shown isolated cases of resistance. However, our new study shows that resistant isolates are becoming more and more common, especially with clinical implications [delayed parasite clearance], ”Said lead author Dr Aline Uwimana, of the Rwanda Biomedical Center, in Kigali.
The experts called for more intensive monitoring of drug resistance in Rwanda and other African countries. “Our study has shown that the treatment for malaria in Rwanda is still 94% effective, but that new studies and ongoing monitoring are urgently needed,” said co-author Dr. Naomi Lucchi, CDC resident adviser to the US President’s Malaria Initiative, said.
The researchers monitored the treatment of 224 children with malaria from six months to five years in three areas of Rwanda – Masaka, Rukara and Bugarama. At two of the sites, about 15% of the children still had detectable parasites after three days, which meet the World Health Organization’s (WHO) criteria for partial resistance.
The researchers also found certain mutations in the parasites, implicated by the WHO in delayed clearance.
Experts believe the warning signs are there. This study and other data suggest that we are ‘at the point of clinically significant resistance to artemisinin in Africa, as it emerged in Southeast Asia a decade ago,’ writes Prof Philip Rosenthal, of the University of California, San Francisco, in a commentary in the journal.
‘Loss of effectiveness of important ACTS [artemisinin-based combination therapies], especially artemether lumefantrine, the most widely used malaria remedy, can have serious consequences, as occurred when resistance to chloroquine led to a huge increase in malaria deaths in the late 20th century. ‘
It was impossible to predict the rate of progression in Africa, but close monitoring of the development of resistance in the parasite – with the immediate replacement of weakened regimes – “could save many lives”, he said.