Table 3. Univariable associations between the presence of C. burnetii in PM10 and spatial, temporal and spatial-temporal characteristics.
| Variable type | Variables | OR | 95% CI | P-value |
|---|---|---|---|---|
| Spatial | Number of goats1 on nearest goat farm (in hundreds) | 0.98 | 0.92–1.04 | 0.418 |
| Distance2 to nearest goat farm (per 100 m) | 0.80 | 0.61–1.08 | 0.105 | |
| Number of goats (in hundreds)/ squared distance (per 100 m) | 1.23 | 1.08–1.40 | 0.002 | |
| Number of goats within 500m buffer (per hundred) | 0.99 | 0.93–1.05 | 0.606 | |
| Number of goats within 1000m buffer (per hundred) | 1.00 | 0.98–1.01 | 0.576 | |
| Number of sheep within 500m buffer (per hundred)3 | - | - | - | |
| Number of sheep within 1000m buffer (per hundred) | 0.98 | 0.82–1.17 | 0.817 | |
| Number of cows within 500m buffer (per hundred) | 0.98 | 0.90–1.08 | 0.659 | |
| Number of cows within 1000m buffer (per hundred) | 0.99 | 0.95–1.02 | 0.372 | |
| Nearest goat farm bulk-milk positive4 | 2.26 | 1.16–4.53 | 0.011 | |
| Temporal | Temperature (per °C) | 0.82 | 0.73–0.91 | <0.001 |
| Relative Humidity (per %) | 0.96 | 0.93–0.99 | 0.016 | |
| Precipitation (per 10 mm) | 0.97 | 0.94–1.00 | 0.030 | |
| Wind speed (per 0.1 m/s) | 1.00 | 0.97–1.04 | 0.906 | |
| Sunshine (per 0.1 hours) | 1.41 | 1.04–1.93 | 0.028 | |
| Estimated monthly percentage of number of goats born in the Netherlands (%)5 | 1.08 | 1.04–1.12 | <0.001 | |
| Spatial-temporal | Natural logarithm of number of goats born on nearest farm per measurement week 6 | 1.30 | 0.93–1.84 | 0.134 |
| Percentage of time sampling site downwind from the nearest goat farm | 1.01 | 0.97–1.04 | 0.717 |
1 Number of goats on farm represents the number of goats (in hundreds) on the nearest farm from the measurement site.
2 Distance is the distance between measurement site and nearest goat farm measured in hundreds of meters.
3 There were no sheep within a 500 m buffer at each measurement site
4 Bulk-milk positive outcomes for C. burnetii tested on January 24th 2011
5 Monthly percentage of number of goats born in the Netherlands estimated on basis of the paper of Hermans et al. [[22]]
6 Subset analyses for farm specific kidding data present for 4 out of 8 measurement sites