Table 4.
Final multivariable logistic regression model describing the association between risk factors and detection of bovine respiratory syncytial virus by PCR on pooled broncho-alveolar lavage samples from epidemic respiratory disease in calves1
| Independent variable | Category | n | % positive | b | SE | OR | 95% CI | P-value |
|---|---|---|---|---|---|---|---|---|
| Intercept | −1.3 | 0.5 | 0.01 | |||||
| PI-3 | Negative | 97 | 22.6 | Referent | ||||
| Positive | 10 | 60.0 | 2.6 | 0.9 | 13.4 | 2.1–86.0 | 0.02 | |
| Season | Autumn | 40 | 12.5 | Referent | <0.001 | |||
| Winter* | 45 | 48.9 | 2.3 | 0.7 | 10.3 | 2.8–37.5 | <0.001 | |
| Spring-summer | 22 | 4.5 | −1.2 | 1.3 | 0.30 | 0.03–3.5 | 0.33 | |
| Number of days with signs before sampling (per day) | 107 | −0.01 | 0.0 | 0.99 | 0.98–0.99 | 0.01 | ||
| Prevalence of calves with respiratory disease (per 1% increase) | 107 | 0.03 | 0.01 | 1.02 | 1.00–1.04 | <0.01 |
1
PI-3 = parainfluenzavirus type 3; b = regression coefficient; OR = odds ratio.
*
Winter was also significantly higher than spring-summer (P < 0.01).