Drug-resistant malaria may spread, India warned

A new research has warned that drug-resistant malaria parasites on the border of Thailand and Myanmar may spread to India and then to Africa, where most deaths from malaria occur.

According to the research, the malaria parasites on the border are becoming resistant to the most effective malaria drugs, a release from The University of Oxford said.

"The concern is that this will open the way for resistance to spread to India and then Africa, where most deaths from malaria occur.

Eliminating malaria might then prove impossible", the release warned.

In the past, resistance to anti-malarial drugs has spread from South-East Asia to Africa.The new cases of resistance have been observed 800km away, at the Thailand-Myanmar border.

The new research from a joint programme between Oxford University and Mahidol University in Thailand has been reported in The Lancet.

The study coincides with research by the same group published in the journal Science.Along with colleagues in the USA, they identify a major region of the malaria parasite genome that is associated with resistance to these drugs.

The most effective antimalarial drug is artemisinin.

The artemisinin derivatives, most commonly artesunate, have the advantage of acting more rapidly and having fewer side-effects than other antimalarial drugs and, until recently, malaria parasites had shown no resistance against them, the release said.

The drugs are recommended to be used only in conjunction with one or more other drugs as Artemisinin-based Combination Therapies (ACTs) because of fears over the possible development of resistance.

ACTs have contributed substantially to the recent decline in malaria cases in most regions.

Resistance to artemisinin makes the drugs less effective and could eventually render them obsolete, putting millions of lives at risk. 

Francois Nosten, Director of the Shoklo Malaria Research Unit – where the work was carried out – and professor of tropical medicine at Oxford University, said: "We have now seen the emergence of malaria resistant to our best drugs, and these resistant parasites are not confined to western Cambodia.

"This is very worrying indeed and suggests that we are in a race against time to control malaria in these regions before drug resistance worsens and develops and spreads further".

In the Lancet study, Oxford-Mahidol University researchers based at the Shoklo Malaria Research Unit on the border of Thailand and Myanmar measured the time taken to clear parasites from the blood stream of over 3,000 patients over a 10 year period between 2001 and 2010.

The average time taken to reduce the number of parasites in the blood by a half – known as the ‘parasite clearance half-life’ – increased from 2.6 hours in 2001 to 3.7 hours in 2010.

This is a clear sign that the drugs are becoming less effective.

The proportion of slow-clearing infections – defined as a half-life of over 6.2 hours – increased over this same period from 6 out of every 1000 infections to 200 out of every 1000 infections.

By examining the genetic make-up of the parasites, the researchers provide compelling evidence that the decline in parasite clearance rates is due to genetic changes in the parasites which make them resistant to the drugs.

This finding is supported by the evidence reported in Science identifying a region in the genome of the P.falciparum malaria parasite that shows a strong association with slow parasite clearance rates.

While the actual mechanism involved is not clear, the region contains several candidate genes that may confer artemisinin resistance to the parasite.

Professor White of Oxford University, who is chair of the WorldWide Antimalarial Resistance Network (WWARN), added: "This new study suggests that containing the spread of resistance is going to be even more challenging and difficult than we had first feared."