EDP Sciences logo
Search
Menu
All issues Volume 41 / No 3 (May–June 2010) Vet. Res., 41 3 (2010) 28 Full HTML
Open Access

Table I.

Results of the multivariate analysis for factors associated with risk of HPAI H5N1 in chicken and duck flocks from 3 July 2004 to 5 May 2005 in Thailand (p ≤ 0.05).

Variable Categories Number of subdistricts Chicken flocks
 Duck flocks
Risk ratio 95% CI Risk ratio 95% CI
(a) Environmental factors
Relative risk for ducks
≤ 0.5 2 769 1.00
0.51–1.5 825 0.76 0.63–0.91
1.51–10 1 310 1.86 1.55–2.22
≥ 10.01 2 462 13.11 10.92–15.73
Relative risk for chickens
≤ 0.5 3 175 1.00
0.51–1.5 633 1.10 0.86–1.42
1.51–10 1 824 6.13 4.83–7.78
≥ 10.01 1 734 33.86 26.33–43.53
Average altitude (m)
≥ 400.01 632 1.00 1.00
150.01–400 2 605 0.38 0.32–0.45 0.27 0.21–0.34
50.01–150 1 701 0.53 0.45–0.63 0.24 0.19–0.30
≤ 50 2 428 5.73 4.77–6.90 10.16 7.89–13.09
Mean number of rice crops per year
≤ 0.2 1 167 1.00 1.00
0.21–1 2 405 0.77 0.65–0.92 0.88 0.70–1.10
1.01–1.5 3 308 1.47 1.24–1.76 1.12 0.88–1.42
≥ 1.51 486 11.21 9.15–13.73 17 12.89–22.42
Distance to the closest river (km)
≥ 10.01 1 328 1.00 1.00
5.01–10 1 509 0.68 0.57–0.82 0.59 0.47–0.75
2.01–5 1 966 0.83 0.69–0.99 0.74 0.58–0.94
≤ 2 2 563 2.05 1.71–2.46 2.88 2.25–3.69
(b) Poultry farming factors
Density of native chickens (no poultry/km2)
≤ 50 1 441 1.00 1.00
50.01–100 1 324 1.12 0.94–1.33 1.57 1.24–2.00
100.01–300 3 319 0.73 0.61–0.87 0.52 0.41–0.66
≥ 300.01 1 282 0.52 0.43–0.63 0.46 0.36–0.60
Density of fighting cocks (no poultry/km2)
≤ 0.1 4 191 1.00 1.00
0.11–1 1 682 0.59 0.50–0.71 0.53 0.42–0.67
1.01–3 832 0.75 0.62–0.91 0.62 0.48–0.80
≥ 3.01 661 1.52 1.24–1.87 2.3 1.75–3.03
Density of houses with fighting cocks (no house/km2)
≤ 0.01 3 152 1.00 1.00
0.01–0.1 2 163 0.67 0.56–0.79 0.69 0.55–0.87
0.11–0.4 1 439 0.86 0.71–1.04 0.73 0.57–0.94
≥ 0.41 612 1.26 1.01–1.54 1.59 1.21–2.10
Density of free-grazing ducks (no poultry/km2)
≤ 0.1 5 953 1.00 1.00
0.11–10 779 0.68 0.57–0.83 0.37 0.29–0.48
≥ 10.01 634 10.13 8.29–12.37 18.26 13.88–24.04
Density of farms with free-grazing ducks (no farm/km2)
≤ 0.001 4 539 1.00 n.s. n.s.
0.0011–0.05 1 367 0.65 0.54–0.78 n.s. n.s.
≥ 0.051 1 460 1.61 1.33–1.96 n.s. n.s.
Density of broiler and layer chickens (no poultry/km2)
≤ 1 2 997 n.s. n.s. 1.00
1.01–50 2 475 n.s. n.s. 0.78 0.61–0.98
50.01–500 1 076 n.s. n.s. 0.68 0.53–0.88
≥ 500.01 818 n.s. n.s. 3.04 2.34–3.95
Density of farms with broiler and layer chickens (no farm/km2)
≤ 0.01 932 1.00 1.00
0.011–0.05 1 092 0.78 0.65–0.93 0.75 0.59–0.94
0.051–1 4 794 1.01 0.85–1.21 1.03 0.81–1.31
≥ 1.01 548 0.61 0.50–0.75 0.66 0.50–0.87
Density of broiler and layer ducks (no poultry/km2)
≤ 5 3 374 1.00 1.00
5.01–20 2 195 0.96 0.80–1.15 0.62 0.49–0.79
20.01–80 1 222 0.97 0.81–1.17 0.51 0.39–0.65
≥ 80.01 575 4.6 3.76–5.63 6.85 5.19–9.04
Density of farms with broiler and layer ducks (no farm/km2)
≤ 0.5 3 228 1.00 1.00
0.51–1 1 471 1.41 1.18–1.69 1.32 1.03–1.69
1.01–2 1 423 1.22 1.02–1.47 0.88 0.69–1.13
≥ 2.01 1 244 0.7 0.58–0.84 0.28 0.22–0.36
(c) Anthropogenic factors
Road density
≤ 0.001 1 897 1.00 1.00
0.0011–0.002 1 849 0.73 0.61–0.87 0.68 0.54–0.86
0.0021–0.005 2 538 0.69 0.58–0.82 0.46 0.36–0.58
≥ 0.0051 1 082 4 3.32–4.82 6.82 5.29–8.80
Density of human population (km2)
≤ 100 2 206 1.00 1.00
100.01–300 3 744 0.86 0.72–1.02 0.57 0.45–0.72
300.01–600 758 2.61 2.15–3.18 4.18 3.19–5.46
≥ 600.01 658 5.56 4.62–6.68 11.61 9.04–14.90
Distance to the closest highway (km)
≥ 50.01 1 021 1.00 1.00
20.01–50 2 109 0.76 0.64–0.91 0.52 0.41–0.66
5.01–20 2 494 1.19 0.99–1.43 1.28 1.01–1.64
≤ 5 1 742 1.96 1.63–2.35 2.84 2.21–3.63
Distance to the closest highway junction (km)
≥ 100.01 1 964 1.00 1.00
50.01–100 2 569 0.78 0.66–0.94 0.78 0.61–0.99
20.01–50 1 863 2.09 1.75–2.51 2.81 2.19–3.60
≤ 20 970 6.15 5.13–7.38 9.46 7.38–12.13
Distance to the closest major city (km)
≥ 80.01 3 427 1.00 1.00
40.01–80 2 176 1.15 0.96–1.37 1.02 0.80–1.30
20.01–40 965 1.78 1.48–2.15 2.06 1.60–2.66
≤ 20 798 4.14 3.44–4.98 7.12 5.53–9.15