TABLE 1.
Significant determinants of the numbers of neutrophils and of A. phagocytophilum-infected neutrophils per milliliter in whole-blood samples of the study sheep in multivariable regression models
| Factor | Effect on no. of neutrophils/ml of blood
|
Effect on no. of infected neutrophils/ml of blood
|
||
|---|---|---|---|---|
| Coefficient (SE) | Wald Z (P)b | Coefficient (SE) | Wald Z (P)b | |
| Number of adult ticks per sheep | −0.215 (0.062) | −3.497 (<0.001) | −0.298 (0.124) | −2.400 (0.016) |
| Number of nymphal ticks per sheep | 0.109 (0.052) | 2.058 (0.037) | 0.113 (0.061) | 1.865 (0.062) |
| Proportion of neutrophils infected | 0.048 (0.011) | 4.424 (<0.001) | 1.448 (0.300) | 4.828 (<0.001) |
| Wk pre- vs wk postinfectiona | −2.737 (0.287) | −9.534 (<0.001) | ||
| Intercept | 7.886 (0.503) | 15.658 (<0.001) | −2.152 (0.272) | −7.902 (<0.001) |
| Random effect of sheep identity | 0.635 (0.166) | 3.826 (<0.001) | ||
a
The time point of infection was defined as the first occasion when blood from an individual sheep was found to be PCR positive.
b
Wald Z values represent parameter estimates divided by their asymptotic standard errors.