Focused Screening and Treatment (FSAT): a PCR-based strategy to detect malaria parasite carriers and contain drug resistant P. falciparum, Pailin, Cambodia.
Recent studies have shown that Plasmodium falciparum malaria parasites in Pailin province, along the border between Thailand and Cambodia, have become resistant to artemisinin derivatives. To better define the epidemiology of P. falciparum populations and to assess the risk of the possible spread of these parasites outside Pailin, a new epidemiological tool named "Focused Screening and Treatment" (FSAT), based on active molecular detection of asymptomatic parasite carriers was introduced in 2010. Cross-sectional malariometric surveys using PCR were carried out in 20 out of 109 villages in Pailin province. Individuals detected as P. falciparum carriers were treated with atovaquone-proguanil combination plus a single dose of primaquine if the patient was non-G6PD deficient. Interviews were conducted to elicit history of cross-border travel that might contribute to the spread of artemisinin-resistant parasites. After directly observed treatment, patients were followed up and re-examined on day 7 and day 28. Among 6931 individuals screened, prevalence of P. falciparum carriers was less than 1%, of whom 96% were asymptomatic. Only 1.6% of the individuals had a travel history or plans to go outside Cambodia, with none of those tested being positive for P. falciparum. Retrospective analysis, using 2010 routine surveillance data, showed significant differences in the prevalence of asymptomatic carriers discovered by FSAT between villages classified as "high risk" and "low risk" based on malaria incidence data. All positive individuals treated and followed-up until day 28 were cured. No mutant-type allele related to atovaquone resistance was found. FSAT is a potentially useful tool to detect, treat and track clusters of asymptomatic carriers of P. falciparum along with providing valuable epidemiological information regarding cross-border movements of potential malaria parasite carriers and parasite gene flow.
World Health Organization, Global Malaria Programme, Geneva, Switzerland. hoyers@who.int
Stefan
S
Hoyer
Sokomar
S
Nguon
Saorin
S
Kim
Najibullah
N
Habib
Nimol
N
Khim
Sarorn
S
Sum
Eva-Maria
EM
Christophel
Steven
S
Bjorge
Andrew
A
Thomson
Sim
S
Kheng
Nguon
N
Chea
Sovann
S
Yok
Samphornarann
S
Top
Seyha
S
Ros
Uth
U
Sophal
Michelle M
MM
Thompson
Steve
S
Mellor
Frédéric
F
Ariey
Benoit
B
Witkowski
Chhiang
C
Yeang
Shunmay
S
Yeung
Socheat
S
Duong
Robert D
RD
Newman
Didier
D
Menard
D037621:Artemisinins; D053626:Atovaquone / Q000627:therapeutic use; D001483:Base Sequence; D002160:Cambodia / Q000453:epidemiology; D002353:Carrier State / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D003710:Demography; D004338:Drug Combinations; D004351:Drug Resistance / Q000235:genetics*; D006801:Humans; D007407:Interviews as Topic; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology*; D008403:Mass Screening / Q000379:methods*; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000235:genetics*; D016133:Polymerase Chain Reaction; D015995:Prevalence; D011319:Primaquine / Q000627:therapeutic use; D002727:Proguanil / Q000627:therapeutic use; D017422:Sequence Analysis, DNA; D018709:Statistics, Nonparametric
D037621:Artemisinins; D004338:Drug Combinations; C109496:atovaquone, proguanil drug combination; C031327:artemisinin; D011319:Primaquine; D002727:Proguanil; D053626:Atovaquone