Abstract
BackgroundResistance to the artemisinin derivatives in Plasmodium falciparum has emerged in Cambodia and is now spreading throughout South-East Asia. The rapid elimination of P. falciparum seems to be the only viable option to avoid a public health disaster but this is difficult because even in low transmission settings many residents have asymptomatic parasitaemias.MethodsIn response to a large number of malaria cases reported in three remote villages on the Thai-Myanmar border where malaria is endemic and the disease is seasonal, surveys were conducted using an ultra-sensitive qPCR assay (LOD 22 parasites per mL). In one of the villages where it was feasible, mass anti-malarial drug administration was proposed to the population as a potential solution, and this was adopted.ResultsIn the three villages 204/356 (57.3 %), 212/385 (55.1 %) and 195/286 (68.2 %) of the resident populations were positive by qPCR (approximately one-third P. falciparum and two-thirds P. vivax). Of those positive for P. falciparum 62 % carried single point mutations in the P. falciparum kelch protein (a marker of artemisinin resistance). In one of the villages 217 of 674 inhabitants received at least one dose of dihydroartemisinin-piperaquine chemoprevention in June 2012, 155 (71.4 %) received two consecutive months, and 98 (45.2 %) received three treatment doses. The chemoprevention was generally well tolerated. The sub-microscopic reservoir of P. falciparum malaria was eliminated during the six-month follow-up period (prevalence fell from 7 to 0 %); P. vivax malaria persisted (prevalence fell from 35 to 8 %). From June to October 2012 (rainy season) the number of clinical episodes of P. falciparum was six times lower (46), than during the same period in the previous year (290).ConclusionMass drug administration with dihydroartemisinin-piperaquine may be an effective strategy to eliminate P. falciparum rapidly where multi-drug resistance is present.
Highlights
Resistance to the artemisinin derivatives in Plasmodium falciparum has emerged in Cambodia and is spreading throughout South-East Asia
The emergence and spread from Asia to Africa of first chloroquine resistance and anti-folate resistance in P. falciparum led to the loss of millions of lives
Malaria has been substantially underestimated in this area, as in other areas in this region with similar epidemiology [7]
Summary
Resistance to the artemisinin derivatives in Plasmodium falciparum has emerged in Cambodia and is spreading throughout South-East Asia. Relative resistance to artemisinin derivatives has emerged recently in Western Cambodia making it imperative to eliminate these parasites rapidly to prevent their spread. One potential approach recently advocated by the WHO is to screen individuals in endemic areas for malaria and treat those who are positive either by microscopy, rapid tests, or by PCR (Focal Screen and Treat; FSAT) [8]. This approach assumes that most infections will be detected by such methods.
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