Molecular surveillance of artemisinin resistance falciparum malaria among migrant goldmine workers in Myanmar

Abstract

Background: Artemisinin resistance has been reported in Greater Mekong Sub-region countries, including Myanmar. After discovery of artemisinin resistance marker (K13), molecular surveillance on artemisinin resistance in endemic regions have been conducted. As the migrant population represents a high percentage of malaria cases, molecular surveillance of artemisinin resistance among migrant workers is of great concern.

Methods: A cross-sectional survey was conducted in Shwegyin Township, where migrants work in the goldmines. Blood samples were collected from uncomplicated Plasmodium falciparum-infected migrant workers by active and passive cases screening with rapid diagnostic testing (RDT) and microscopy. Amplification and sequence analysis of artemisinin resistance molecular markers, such as k13, pfarps10, pffd, pfmdr2, pfmrp1, pfrad5, and pfcnbp, were carried out and pfmdr1 copy number analysis was conducted by real-time PCR.

Results: Among the 100 falciparum-infected patients, most were male (90%), of working age (20-40 years) with median parasite density of 11,166 parasites/µL (range 270-110,472 parasites/µL). Artemisinin resistance molecular marker, k13 mutations were detected in (21/100, 21.0%) in which composed of a validated marker, C580Y (9/21, 42.9%) and candidate markers such as P574L (5/21, 23.8%), P667T (5/21, 23.8%) and M476I (2/21, 9.5%). Underlying genetic markers predisposing to become k13 mutants were found as V127M of pfarps10 (41/100, 41.0%), D153Y of pffd (64/100, 64.0%), T484I of pfmdr2 (58/100, 58.0%) and F1390I of pfmrp1 (24/100, 24.0%). The pfmdr1 copy number analysis revealed six copy numbers (1/100, 1.0%), three (2/100, 2.0%), two (8/100, 8.0%) and only one copy number (89/100, 89.0%). Only one sample showed both k13 mutation (P667T) and multiple copy number of pfmdr1.

Conclusions: High mutant rate of artemisinin resistance markers and relatively high pfmdr1 copy number among isolates collected from migrant goldmine workers alert the importance of containment measures among this target population. Clinical and molecular surveillance of artemisinin resistance among migrants should be scaled up.

Keywords: Artemisinin resistance; Malaria; Migrant; Molecular surveillance; Myanmar.

Fig. 1

Map of the Bago Region showing the numbers of cases of falciparum malaria diagnosed within each administrative township who reported that they were migrant goldmine workers. The study site, Shwegyin showed the highest reported number of cases of malaria from migrant goldmine workers than from neighbouring areas as of 2010. It is one of the Tier I areas of Myanmar’s artemisinin resistance containment zone

Fig. 2

Occupation of the examined cases and malaria cases in active cases detection. Data were retrieved from the township active case detection [14] report conducted in 2010. Goldmine workers were the majority of malaria cases in this study site. Taung-yar: slash-and-burn cultivation

Fig. 3

Co-occurrence of molecular markers among pfmdr1 multiple and single copy number. The distribution of single and multiple copy number of pfmdr1 gene (a) and co-occurrence of other molecular markers among single and multiple copy number of pfmdr1 gene (b)

Fig. 4

Co-occurrence of the molecular markers among k13 kelch mutant and wild type. Distribution of k13 wild and mutant (a) and co-occurrence of other molecular markers among the k13 mutants and wild-type alleles (b)