LONDON • Malaria-carrying parasites in parts of Cambodia have developed resistance to a major drug used to treat the disease in Southeast Asia, according to research published in The Lancet Infectious Diseases journal.

The drug piperaquine, used in combination with the drug artemisinin, has been the main form of malaria treatment in Cambodia since 2008.

The combination is also one of the few treatments still effective against the multi-drug-resistant malaria which has emerged in South-east Asia in recent years, and which experts fear may spread to other parts of the world.

"(Treatment) failures are caused by both artemisinin and piperaquine resistance, and commonly occur in places where dihydroartemisinin-piperaquine has been used in the private sector," researchers said.

Artemisinin resistance has been found in five countries in South-east Asia: Cambodia, Laos, Myanmar, Thailand and Vietnam. Resistance to artemisinin and drugs used in combination with it has developed in parts of Cambodia and Thailand. Experts are particularly concerned that artemisinin resistance will spread to sub-Saharan Africa where about 90 per cent of malaria cases and deaths occur.

They suggest an alternative treatment should be tested, comprising artesunate, a form of artemisinin, combined with mefloquine, a different long-acting partner drug.

The research was produced by the US National Institute of Allergy and Infectious Diseases.

About 3.2 billion people - almost half the world's population - are at risk of malaria, according to the World Health Organisation (WHO).

Singapore was declared malaria-free by the WHO in 1982, but it remains vulnerable due to the influx of travellers and foreign workers from malaria zones.

REUTERS