Drug-resistant malaria proliferating
Tuesday April 10th, 2012
A strain of malaria that is resistant to standard treatment has been extensively reported along the Thailand-Burma border.
The artemisinin-resistant malaria was confirmed in Cambodia in 2006 and there have been concerted efforts to effort to control P. falciparum malaria and stem its prevalence.
But new research, published in the April 5 edition of The Lancet, has revealed that it is rapidly increasing along the Thailand-Burma (Myanmar) border.
Professor François Nosten and Professor Nicholas White, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand, and Centre for Tropical Medicine at Oxford University in England, and colleagues analysed data from patients in malaria clinics of the Shoklo Malaria Research Unit, located along the northwestern border of Thailand, who received treated between 2001 and 2010.
“Genetically determined artemisinin resistance in P. falciparum emerged along the Thailand–Myanmar border at least eight years ago and has since increased substantially,” they write.
“At this rate of increase, resistance will reach rates reported in western Cambodia in two to six years."
They say that the reduction in artemisinin effectiveness will have an adverse effect on the treatment of uncomplicated falciparum malaria by slowing therapeutic responses and increasing treatment failure rates. It will also reduce the effectiveness of treatment for severe malaria.
“Identification of a molecular marker will be crucial to monitor the distribution and spread of resistance and to understand the evolution of this trait and the mechanism of action of artemisinin,” they say.
“The large numbers of patients infected with malaria, high heritability, and the broad range of parasite clearance half-lives make the Thailand–Myanmar border region ideal for powerful association studies.
“Clinical studies are needed urgently to map further spread and to establish the effect of different degrees of artemisinin resistance on treatment effectiveness and transmissibility.”
Meanwhile, in the April 6 edition of Science, Ian Cheeseman and colleagues from the Texas Biomedical Research Institute in San Antonio, Texas, USA, are reported to have sequenced the genomes of 91 P. falciparum parasites from Thailand, western Cambodia and Laos, where resistance to the latest artemisinin-based drugs has not yet emerged.
They found 33 regions on the P. falciparum genome that appear to be under strong selection for artemisinin resistance and were able to narrow it down to seven specific genes on chromosome 13 that span 35 kilobase pairs.
This particular section of the chromosome is accountable for 35 per cent of the observed reduction in P. falciparum clearance rates in Southeast Asia.
A Major Genome Region Underlying Artemisinin Resistance in Malaria. Cheeseman I et al Science April 5 2012
Tags: Asia | Genetics | North America | Traveller Health | World Health
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