Results of multivariable modelling on SARS-CoV-2 RNA in the different sample types of mink housing units
| Variable | Virus load (copies) | Virus presence (non-detect/detect) | ||
| Swipe | Bedding material | Faecal material | Drinker cup swab | |
| Ratio (95% CI) | Ratio (95% CI) | OR (95% CI) | OR (95% CI) | |
| Farm NB1A (indicator) | – | – | – | – |
| Farm NB1B | 0.43* (0.23 to 0.81) | 1.7 (0.25 to 11) | 0.31 (0.081 to 1.11) | 0.28 (0.061 to 1.09) |
| Farm NB2 | 0.37* (0.20 to 0.68) | 0.22 (0.03 to 1.5) | 0.16* (0.042 to 0.56) | 0.15* (0.031 to 0.58) |
| Farm NB4 | 6.80* (2.90 to 16.0) | 45* (3.0 to 670) | 0.19 (0.025 to 1.28) | 1.92 (0.296 to 14.32) |
| Timepoint 1 (indicator) | – | – | – | – |
| Timepoint 2 | 1.10 (0.60 to 2.00) | 1.7 (0.24 to 11) | 0.4 (0.115 to 1.28) | 0.25* (0.058 to 0.97) |
| Timepoint 3 | 0.57 (0.31 to 1.10) | 0.86 (0.12 to 6.0) | 0.11* (0.027 to 0.38) | 0.22* (0.045 to 0.88) |
| Mink recently deceased (vs live mink) | 1.60 (0.95 to 2.60) | 59* (12 to 300) | 0.47 (0.161 to 1.31) | 7.76* (2.156 to 38.32) |
Number of samples (percentage above limit of detection) collected per type: swipe n=99 (100%), bedding material n=94 (83%), faecal material n=95 (54%) and drinker cup swab n=97 (31%).
Censored regression was applied for swipes and bedding material samples. Associations expressed in ratio=estimate of associations to the power of 10 to represent ratio in viral load.
Logistic regression was applied for faecal material samples and swabs of the drinker cups due to the limited number of samples above the limit of detection. Associations expressed in OR.
*P<0.05.