Background
Methods
Study site and design
Study participants and procedures
Sample collection
DNA extraction and PCR amplification
Statistical analysis
Ethics statement
Results
Demographic characteristics of participants
Characteristics | Results | P value** | ||||
---|---|---|---|---|---|---|
Negative | Positive | |||||
P. falciparum
|
P. vivax
| Mixed (Pf + Pv)a
|
Plasmodium spp. | |||
Sex | ||||||
Male (n = 479) | 354 (74 %) | 16 (3 %) | 76 (16 %) | 10 (2 %) | 23 (5 %) | <0.001 |
Female (n = 409) | 359 (88 %) | 16 (4 %) | 23 (6 %) | 4 (1 %) | 7 (2 %) | |
Age group | ||||||
15–35 years (n = 505) | 383 (76 %) | 22 (4 %) | 73 (15 %) | 8 (2 %) | 19 (4 %) | 0.009 |
36–55 years (n = 234) | 196 (84 %) | 7 (3 %) | 20 (9 %) | 5 (2 %) | 6 (3 %) | |
56–80 years (n = 149) | 134 (90 %) | 3 (2 %) | 6 (4 %) | 1 (0.7 %) | 5 (3 %) | |
Mean age in years (n = 888; SD) | 37.0 (16.2) | 32.0 (13.9) | 30.9 (13.6) | 32.9 (13.9) | 34.7 (15.7) | 0.005 |
History of Fever in the last 48 h | ||||||
Yes (n = 277) | 223 (80 %) | 17 (6 %) | 26 (9 %) | 4 (1 %) | 7 (3 %) | 0.056 |
No (n = 611) | 490 (80 %) | 15 (3 %) | 73 (12 %) | 10 (2 %) | 23 (4 %) | |
Feeling ill in the last 48 h | ||||||
Yes (n = 451) | 370 (82 %) | 20 (4 %) | 43 (10 %) | 5 (1 %) | 13 (3 %) | 0.186 |
No (n = 437) | 343 (79 %) | 12 (3 %) | 56 (13 %) | 9 (2 %) | 17 (4 %) | |
History of malaria | ||||||
Yes (n = 493) | 367 (74 %) | 21 (4 %) | 76 (15 %) | 10 (2 %) | 19 (4 %) | <0.001 |
No (n = 385) | 336 (87 %) | 11 (3 %) | 23 (6 %) | 4 (1 %) | 11(3 %) | |
Episodes of malaria | ||||||
0 Episodes (n = 395) | 346 (88 %) | 11 (3 %) | 23 (6 %) | 4 (1 %) | 11 (3 %) | <0.001 |
1–3 episodes (n = 409) | 320 (78 %) | 20 (5 %) | 47 (12 %) | 7 (2 %) | 15 (4 %) | |
>3 episodes (n = 84) | 47 (56 %) | 1 (1 %) | 29 (35 %) | 3 (4 %) | 4 (5 %) | |
Stay overnight in the forest in the last 3 monthsa
| ||||||
<2 weeks ago (n = 183) | 136 (74 %) | 7 (4 %) | 30 (16 %) | 3 (2 %) | 7 (4 %) | <0.001 |
2–4 weeks ago (n = 27) | 16 (59 %) | 1 (4 %) | 8 (30 %) | 1 (4 %) | 1 (4 %) | |
>4 weeks ago (n = 66) | 43 (65 %) | 1 (2 %) | 15 (23 %) | 4 (6 %) | 3 (5 %) | |
No forest visits (n = 612) | 518 (85 %) | 23 (4 %) | 46 (8 %) | 6 (1 %) | 19 (3 %) | |
Travelled outside the village in the last 3 monthsa
| ||||||
Yes (n = 232) | 188 (81 %) | 10 (4 %) | 23 (10 %) | 4 (2 %) | 7 (3 %) | |
No (n = 656) | 525 (80 %) | 22 (3 %) | 76 (12 %) | 10 (2 %) | 23 (4 %) | 0.902 |
Bed net use | ||||||
Every day (n = 682) | 559 (82 %) | 26 (4 %) | 67 (10 %) | 8 (1 %) | 22 (3 %) | 0.132 |
Sometimes (n = 143) | 108 (76 %) | 3 (2 %) | 24 (17 %) | 4 (3 %) | 4 (3 %) | |
Never (n = 63) | 46 (73 %) | 3 (5 %) | 8 (13 %) | 2 (3 %) | 4 (6 %) |
Prevalence of Plasmodium infections
Villages | Negative | Positive | PfK-13 resistance Marker C580Y | |||
---|---|---|---|---|---|---|
PF
|
PF + PV
|
PV
|
P species
| |||
Thapangthong District | ||||||
Maiphosy (n = 50) | 38 (76 %) | 0 | 1 (2 %) | 11 (22 %) | 0 | 1/1 (100 %) |
Bouttaphan (n = 59) | 42 (71 %) | 1 (2 %) | 2 (3 %) | 14 (24 %) | 0 | 3/3 (100 %) |
Maixe (n = 58) | 47 (81 %) | 2 (3 %) | 0 | 7 (12 %) | 2 (3 %) | 1/2 (50 %) |
Phouphanang (n = 56) | 37 (66 %) | 2 (4 %) | 1 (2 %) | 15 (27 %) | 1 (2 %) | 3/3 (100 %) |
Phoumaly (n = 52) | 42 (81 %) | 1 (2 %) | 1 (2 %) | 6 (12 %) | 2 (4 %) | 2/2 (100 %) |
Nalao (n = 52) | 40 (77 %) | 1 (2 %) | 2 (4 %) | 7 (13 %) | 2 (4 %) | 0/3 |
Khampia (n = 49) | 30 (61 %) | 1 (2 %) | 1 (2 %) | 14 (29 %) | 3 (6 %) | 2/2 (100 %) |
Kengkhai (n = 57) | 50 (88 %) | 0 | 0 | 3 (5 %) | 4 (7 %) | 0/0 |
Thapangthong Total (n = 433) | 326 (75 %) | 8 (2 %) | 8 (2 %) | 77 (18 %) | 14 (3 %) | 12/16 (75 %) |
Nong District | ||||||
Oi Tan Tip (n = 50) | 22 (44 %) | 4 (8 %) | 5 (10 %) | 15 (30 %) | 4 (8 %) | 0/8 |
Denvilay (n = 50) | 46 (92 %) | 1 (2 %) | 0 | 2 (4 %) | 1 (2 %) | 0/1 |
Asing na (n = 19) | 15 (79 %) | 1 (5 %) | 0 | 2 (11 %) | 1 (5 %) | 0/1 |
Asing saly (n = 29) | 27 (93 %) | 0 | 0 | 0 | 2 (7 %) | 0/0 |
Phounmakmy (n = 57) | 46 (81 %) | 9 (16 %) | 0 | 0 | 2 (4 %) | 0/8 |
Kaysone (n = 50) | 46 (92 %) | 2 (4 %) | 0 | 1 (2 %) | 1 (2 %) | 0/1 |
Thathe (n = 49) | 45 (92 %) | 1 (2 %) | 1 (2 %) | 1 (2 %) | 1 (2 %) | 1/2 (50 %) |
Xuangtai (n = 50) | 44 (88 %) | 3 (6 %) | 0 | 0 | 3 (6 %) | 0/1 |
Paloy (n = 47) | 45 (96 %) | 1 (2 %) | 0 | 1 (2 %) | 0 | 1/1 (100 %) |
Salang (n = 54) | 51 (94 %) | 2 (4 %) | 0 | 0 | 1 (2 %) | 0/2 |
Nong Total (n = 455) | 387 (85 %) | 24 (5 %) | 6 (1 %) | 22 (5 %) | 16 (4 %) | 2/28 (7 %) |
Overall Total (n = 888) | 713 (80 %) | 32 (4 %) | 14 (2 %) | 99 (11 %) | 30 (3 %) | 14/44 (32 %) |
Resistance markers
Plasmodium prevalence by RDT
RDT | qPCR | |||||
---|---|---|---|---|---|---|
Negative |
P. falciparum
|
P. vivax
| Mixeda
|
Plasmodium spp. | Total | |
Negative | 708 | 23 | 96 | 13 | 30 | 870 |
P. falciparum
| 0 | 7 | 0 | 1 | 0 | 8 |
Non-falciparum | 4 | 0 | 2 | 0 | 0 | 6 |
Mixed infectiona
| 1 | 2 | 1 | 0 | 0 | 4 |
Total | 713 | 32 | 99 | 14 | 30 | 888 |
RDT | |||||
---|---|---|---|---|---|
Sensitivity % (95 % CI) | Specificity % (95 % CI) | PPV (95 % CI) | NPV (95 % CI) | ||
uPCR |
P. falciparum (n = 36) | 27.8 (14.2–45.2) | 99.9 (99.1–100) | 90.9 (57.1–99.5) | 96.5 (94.8–97.6) |
P. vivax (n = 109) | 2.7 (0.7–8.2) | 99.3 (98.3–99.7) | 37.5 (10.2–74.1) | 86.7 (84.1–88.9) |
Factors associated with Plasmodium infections
Covariates | Univariate analysis | P value | Multivariate analysis | P value |
---|---|---|---|---|
Crude OR (95 % CI) | Adj. OR (95 % CI) | |||
Sex male (n = 812) | 3.35 (2.06–5.46) | <0.001 | 4.76 (2.84–8.00)a
| <0.001 |
Age (n = 812) | 0.97 (0.96–0.99) | 0.001 | 0.98 (0.96–0.99)b
| 0.002 |
District Nong (n = 812) | 0.21 (0.13–0.34) | <0.001 | 0.16 (0.10–0.27)c
| <0.001 |
History of Fever in the previous 48 h (n = 812) | 0.78 (0.49–1.26) | 0.31 | 1.02 (0.61–1.72)d
| 0.92 |
Feeling ill in the previous 48 h (n = 812) | 0.71 (0.47–1.09) | 0.12 | 0.98 (0.62–1.55)d
| 0.92 |
History of 3 or more malaria episodes (n = 802) | 9.28 (4.96–17.36) | <0.001 | 1.56 (1.08–2.25)d
| 0.02 |
Stay overnight in the forest in the last 3 months (n = 812) | 3.06 (2.00–4.70) | <0.001 | 2.45 (1.17–5.11)d
| 0.02 |
Travelled outside the village in the last 3 months (n = 812) | 0.85 (0.51–1.39) | 0.50 | 0.92 (0.54–1.57)d
| 0.76 |
Bed net never used (n = 812) | 1.28 (0.58–2.79) | 0.31 | 1.55 (0.66–3.66)d
| 0.45 |
Covariates | Univariate analysis | P value | Multivariate analysis | P value |
---|---|---|---|---|
Crude OR (95 % CI) | OR adj. (95 % CI) | |||
Sex male (n = 745) | 1.01 (0.50–2.06) | 0.97 | 0.84 (0.87–4.65)a
| 0.65 |
Age (n = 745) | 0.97 (0.96–1.00) | 0.01 | 0.98 (0.95–1.00)b
| 0.08 |
District Nong (n = 745) | 1.89 (0.84–4.3) | 0.12 | 2.02 (0.87–4.65)c
| 0.10 |
History fever in the last 48 h (n = 745) | 2.49 (1.22–5.08) | 0.01 | 2.47 (1.20–5.08)d
| 0.01 |
Feeling ill in the last 48 h (n = 745) | 1.55 (0.74–3.21) | 0.24 | 1.70 (0.81–3.59)d
| 0.16 |
History of any malaria (n = 735) | 1.75 (0.83–3.68) | 0.14 | 1.68 (0.79–3.61)d
| 0.18 |
History of 3 or more malaria episodes (n = 735) | 0.67 (0.09–5.30) | 0.70 | 0.87 (0.10–7.40)d
| 0.90 |
Stay overnight in the forest in the previous 3 months (n = 745) | 1.04 (0.47–2.28) | 0.92 | 1.04 (0.44–2.41)d
| 0.94 |
Travelled outside the village in the previous 3 months (n = 745) | 1.27 (0.59–2.73) | 0.54 | 1.91 (0.55–2.58)d
| 0.66 |
Bed net never used (n = 745) | 1.50 (0.44–5.11) | 0.52 | 1.18 (0.34–4.10)d
| 0.80 |