Table 2.

Relative risk (odds ratio) for trichostrongyle infections and the quantitative egg output in relation to different variables. Single regression model on ± trichostrongyle faecal egg positive animals. Differences between related figures are statistically significant (p < 0.05).

Categories, examined animals and variables	Relative risk of infection		EPG
	Odds ratio	95% Cl	Geometric mean
Lambing time
Ewes soon after lambing
Winter	1	-	13
Spring	8.3	3.4 – 20.1	123
High EPG – values
Ewes soon after lambing
Haemonchus negative flocks	1	-	118
Haemonchus positive flocks	26	10 – 71	776
Different sampling times in the same flocks
Lambs in Sept. – Oct.	1	-	37
Lambs in Nov.	5.0	2.8 – 8.7	213
Slaughtering time
Lambs in Sept. – Oct.
All lambs slaughtered before Dec. 1	1	-	10
≥ 1% of the lambs slaughtered after Dec 1.	3.9	2.5 – 6.1	83
Accommodation from birth to turn out in spring
Lambs after appr. 4 weeks grazing
Stable – new grazing area	1	-	3
Stable – old grazing area	3.8	2.4 – 5.9	22
Winter area – new grazing area	2.3	1.6 – 3.3	10
Winter area – old grazing area	9.1	5.6 – 14.6	63
Permanent outdoors	3.9	2.4 – 6.3	25
Pasture managament
Ewes not dewormed
Lambs after appr. 4 weeks grazing
New grazing area	1	-	4
Old grazing area	5.9	4.3 – 7.9	53
Ewes dewormed before turn out
Lambs after appr. 4 weeks grazing
New grazing area	1	-	4
Old grazing area	4.9	2.4 – 10.0	45
Lambs in Sept. – Oct.
New spring grazing area + New autumn grazing area	1	-	8
New spring grazing area + Old autumn grazing area	7.4	2.9 – 19.3	156