Novel Cross-Border Approaches to Optimise Identification of Asymptomatic and Artemisinin-Resistant Plasmodium Infection in Mobile Populations Crossing Cambodian Borders.
BACKGROUND
Human population movement across country borders presents a real challenge for malaria control and elimination efforts in Cambodia and its neighbouring countries. To quantify Plasmodium infection among the border-crossing population, including asymptomatic and artemisinin resistant (AR) parasites, three official border crossing points, one from each of Cambodia's borders with Thailand, Laos and Vietnam, were selected for sampling.


RESULTS
A total of 3206 participants (of 4110 approached) were recruited as they crossed the border, tested for malaria and interviewed. By real-time polymerase chain reaction (RT-PCR), 5.4% of all screened individuals were found to harbour Plasmodium parasites. The proportion was highest at the Laos border (11.5%). Overall there were 97 P. vivax (55.7%), 55 P. falciparum (31.6%), two P. malariae (1.1%) and 20 mixed infections (11.5%). Of identified infections, only 20% were febrile at the time of screening. Of the 24 P. falciparum samples where a further PCR was possible to assess AR, 15 (62.5%) had mutations in the K13 propeller domain gene, all from participants at the Laos border point. Malaria rapid diagnostic test (RDT) pLDH/HRP-2 identified a positivity rate of 3.2% overall and sensitivity compared to RT-PCR was very low (43.1%). Main individual risk factors for infection included sex, fever, being a forest-goer, poor knowledge of malaria prevention methods and previous malaria infection. Occupation, day of the week and time of crossing (morning vs. afternoon) also appeared to play an important role in predicting positive cases.


CONCLUSIONS
This study offers a novel approach to identify asymptomatic infections and monitor AR parasite flow among mobile and migrant populations crossing the borders. Similar screening activities are recommended to identify other hot borders and characterise potential hot spots of AR. Targeted "customised" interventions and surveillance activities should be implemented in these sites to accelerate elimination efforts in the region.
Malaria Consortium, Phnom Penh, Cambodia.
Hannah M
HM
Edwards
Malaria Consortium, Phnom Penh, Cambodia.
Sara E
SE
Canavati
Malaria Consortium, Phnom Penh, Cambodia.
Chandary
C
Rang
National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia.
Po
P
Ly
National Center for Parasitology, Entomology and Malaria Control (CNM), Phnom Penh, Cambodia.
Siv
S
Sovannaroth
Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.
Lydie
L
Canier
Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.
Nimol
N
Khim
Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.
Didier
D
Menard
Malaria Consortium, Phnom Penh, Cambodia.
Ruth A
RA
Ashton
Malaria Consortium, Phnom Penh, Cambodia.
Sylvia R
SR
Meek
Malaria Consortium, Phnom Penh, Cambodia.
Arantxa
A
Roca-Feltrer
D000293:Adolescent; D000328:Adult; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D058345:Asymptomatic Infections / Q000453:epidemiology*; D002160:Cambodia / Q000453:epidemiology; D002353:Carrier State / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D004351:Drug Resistance; D004641:Emigration and Immigration; D005260:Female; D006801:Humans; D007812:Laos / Q000453:epidemiology; D008288:Malaria / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology; D008297:Male; D010961:Plasmodium / Q000235:genetics / Q000302:isolation & purification*; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D010965:Plasmodium malariae / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D012307:Risk Factors; D013785:Thailand / Q000453:epidemiology; D014171:Transients and Migrants; D014744:Vietnam / Q000453:epidemiology; D055815:Young Adult
D000962:Antimalarials; D037621:Artemisinins; C031327:artemisinin