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Table 2 Malariometric indices by study village (determined by microscopy and PCR)

From: Epidemiology of forest malaria in Central Vietnam: the hidden parasite reservoir

  Village 1% (n) Village 2 Village 3 Village 4 TOTAL % (n/N) [95% CI]
Total screened (by microscopy) 350 256 532 312 1,450
Parasite prevalence (microscopy) 4.9 (17) 3.9 (10) 9.8 (52) 10.9 (34) 7.8 (113/1450) [6.3; 9.6]°
Prevalence by age group (years):       
 ≤9 4.7 (6/127) 1.2 (1/84) 9.9 (20/202) 15.4 (18/117) 8.5 (45/530) [6.3; 11.3] °°
 10–19 7.6 (5/66) 7.6 (4/53) 25.6 (20/78) 11.4 (8/70) 13.9 (37/267) [9.4; 20.0]
 20–39 4.2 (4/95 5.3 (4/75) 5.6 (9/160) 7.9 (6/76) 5.7 (23/406) [3.8; 8.3]
 ≥40 3.2 (2/62) 2.3 (1/44) 3.3 (3/92) 4.1 (2/49) 3.2 (8/247) [1.6; 6.4]
Species distribution (proportion):       
- P. falciparum 58.8 (10) 80.0 (8) 96.2 (50) 70.6 (24) 81.4 (92) [72.8; 87.8]°
- P. vivax 41.2 (7) 20.0 (2) 1.9 (1) 29.4 (10) 17.7 (20) [11.6; 26.1]
- Mixed 0 0 1.9 (1) 0 0.9 (1) [0.1; 6.3]
Parasite density (geometric mean):       
 - P. falciparum 1390.9 938.5 2008.3 3007.6 2006.9 [1,523.8; 2,643.1]
 - P. vivax 340.9 423.3 726.6 794.9 559.7 [301.9; 1,037.7]
Infections with gametocytes, % (n) 64.7 (11/17) 40.0 (4/10) 15.4 (8/52) 52.9 (18/34) 36.3 (41/113) [28.0; 45.5]°°
Proportion asymptomatic, % (n) 76.5 (13/17) 80.0 (8/10) 73.1 (38/52) 58.8 (20/34) 69.9 (79/113) [60.1; 78.2]
Total surveyed (PCR) N = 75 N = 55 N = 133 N = 64 N = 327
Parasite prevalence*, % (n) 16.4 (13/75) 18.9 (12/55) 20.2 (25/133) 42.5 (24/64) 23.6 (74/327) [19.0; 28.9]
Species distribution:       
P. falciparum (Pf) 25.8 (4) 52.6 (6) 77.5 (17) 58.6 (14) 59.2 (41) [47.2; 70.2]°
P. vivax (Pv) 74.2 (9) 47.4 (6) 22.5 (8) 37.9 (9) 39.6 (32) [28.7; 51.6]
Pf + Pv 0 0 0 3.5 (1) 1.2 (1) [0.2; 8.7]
Prop. sub-patent infections, % (n) 79.0 (10) 73.7 (8) 44.9 (14) 57.2 (14) 58.7 (46) [46.2; 70.2]
Prop. asymptomatic infections, % (n) 100.0 (13) 71.9 (9) 62.3 (15) 78.6 (18) 75.4 (55) [63.7; 84.2]
Prevalence ratio LM/PCR 0.30 0.21 0.48 0.26 0.33  
Mean haemoglobin, g/dl 13.1 13.4 11.9 11.9 12.4 [12.2; 12.6]**
Prevalence anaemia (Hb <10.0 g/dl) 3.4 (2) 2.7 (1) 14.9 (19) 11.7 (7) 9.6 (29) [6.6; 13.7]°
  1. °Chi-square p < 0.05;
  2. °°Chi-square p < 0.001 (p-values are specified for significant differences between villages for each category);
  3. * Village prevalence was estimated taking into account the survey design (weight = household size; strata = village);
  4. ** Significant Hb decrease by >1.1 g/dl in Villages 3 and 4 compared to Village 1 (svy regress p < 0.05).