A longitudinal study of serological responses to Coxiella burnetii and shedding at kidding among intensively-managed goats supports early use of vaccines

Table 3 Multivariable Weibull accelerated failure-time regression model assessing risk factors for seroconversion to C. burnetii before breeding.

Variable	Levels	n	Serocon.	Coef.	SE (Coef.)	p value	Survival rate ratio (95% CI)	Hazard ratio (95% CI)
Cohort	Cohort 2	62	42	−0.60	0.11	0.001	0.55 (0.39, 0.78)	2.73 (1.45, 5.16)
Cohort	Cohort 1	33	16	0.00 (ref)			1.00	1.00
Doe IgM	Positive	37	29	−0.42	0.16	0.008	0.65 (0.48, 0.89)	2.04 (1.19, 3.54)
Doe IgM	Negative	56	28	0.00 (ref)			1.00	1.00
Intercept	–	–	–	3.89	0.35	< 0.001	–	–

In intensively-reared goats in Victoria, Australia, 2014–2015. Interpretation: After adjusting for the effect of cohort, kids born by does that had positive IgM titres (Doe IgM = positive; indicating recent exposure) were 2.04 times more likely to seroconvert within the first 6 months of life compared to those born by IgM seronegative does. Log likelihood = −201.1. Coef. coefficient. Similarly, after adjusting for the effect of farm, kids born by does that had positive IgM titres were 2.23 times (95% CI 1.29, 3.86) more likely to seroconvert within the first 6 months of life compared to those born by IgM seronegative does; see Additional file 3

ISSN: 1297-9716