Table 7.

Climatic associations with E. coli O157 super-shedding in a cohort of 52 dairy heifers, estimated by logistic regression. Levels for each factor represent the number of days the threshold value for was reached in the 7 days preceding sampling. The exception was temperature (T), which was counted in the 3 days preceding sampling

Parameter	n	Estimate	s.e.	95% CI	P	OR
T <30°C	372	−2·816	0·225	−3·257 to −2·376	n.a.	1
T ⩾30°C, 1 day	233	−1·522	1·225	−2·714 to −0·329	0·012	0·218
T ⩾30°C, 2 days	138	−0·99	2·225	−2·211 to 0·231	0·112	0·371
T ⩾30°C, 3 days	99	−1·764	3·225	−3·688 to 0·160	0·072	0·171
No rain	190	−4·526	0·449	−5·406 to −3·647	n.a.	1
⩾10 mm, 1 day	450	1·636	0·538	0·581 to 2·69	0·002	5·133
⩾10 mm, 2 days	202	2·011	0·547	0·938 to 3·084	<0·001	7·473
RH <95	660	−3·907	0·278	−4·453 to −3·362	n.a.	1
RH ⩾95%, 1 day	182	1·497	0·387	0·738 to 2·257	<0·001	4·47
SE >20, 1 day	103	−2·618	0·392	−3·386 to −1·851	n.a.	1
SE ⩾20, 3 days	123	0·079	0·523	−0·945 to 1·104	0·879	1·083
SE ⩾20, 4 days	49	−6·9	10·4	−27·25 to 13·36	0·502	0·001
SE ⩾20, 5 days	241	−0·753	0·532	−1·795 to 0·289	0·157	0·471
SE ⩾20, 6 days	235	−1·73	0·701	−3·103, −0·356	0·014	0·177
SE ⩾20, 7 days	91	−1·88	1·08	−3·996 to 0·234	0·081	0·152

s.e. Standard error; CI, confidence interval; OR, odds ratio; n.a., not applicable as the reference level; RH, relative humidity; SE, solar exposure.