Table 6 Statistical analysis of metacercariae counts and FZT infection status (not infected, infected) of fish collected in 25 ponds located in two communes, Nhgia Lac and Nhgia Phu, in Nam Dinh province, northern Vietnam during the main FZT transmission season (July-November)
Factor (No. of sites sampled) | No. of fish | Intensity of infection | Infection status | ||
|---|---|---|---|---|---|
| Â | Â | Count ratio (uni-variablea) | Count ratio (multi-variable) | Odds ratio (uni-variablea) | Odds ratio (multi-variable) |
Time of sampling | Â | Â | Â | Â | Â |
 August (25) | 254 | 1.00 |  | 1.00 |  |
 October (22) | 221 | 1.47 | 1.90* | 1.88** | 1.98** |
 December (21) | 213 | 2.77* | 2.98*** | 2.84*** | 3.22*** |
Fish species (ponds) | Â | Â | Â | Â | Â |
  C. idellus (20) | 91 | 1.00 | 1.00 | 1.00 | 1.00 |
  H. molitrix (21) | 192 | 0.80 | 0.63 | ||
  C. mrigala (21) | 90 | 0.07*** | 0.14* | 0.52 | |
 Other species (19) | 119 | 0.21** | 0.26* | 0.34*** | |
  L. rohita (25) | 196 | 0.04*** | 0.04*** | 0.20*** | |
Commune | Â | Â | Â | Â | Â |
 Nghia Lac (12) | 365 | 1.00 |  | 1.00 | 1.00 |
 Nghian Phu (13) | 323 | 1.80 |  | 2.41*** | 2.29*** |
Snail density | Â | Â | Â | Â | Â |
August in ponds | Â | Â | Â | Â | Â |
 None (5) | 119 | 1.00 | 1.00 | 1.00 |  |
 Low (10) | 293 | 1.29 | 1.01 |  | |
 High (10) | 276 | 2.26 | 2.62* | 1.34 |  |
August in small canals | Â | Â | Â | Â | Â |
 Absent (19) | 525 | 1.00 |  | 1.00 |  |
 Present (6) | 163 | 0.61 |  | 0.74 |  |
August in rice fields | Â | Â | Â | Â | Â |
 Absent (17) | 462 | 1.00 |  | 1.00 |  |
 Present (8) | 226 | 0.65 |  | 1.17 |  |