Table 1.

Proportion of samples positive for Salmonella spp. by site and cohort (samples represent individual faecal samples, pooled faecal samples from the source nursery and barn environmental swabs) and respective 95% confidence intervals (CI)

Site/cohort	Environment*		Nursery†		Cohort
					Total positive faecal samples tested, n/N (%)	Adjusted Salmonella apparent prevalence‡
	%	(95% CI)	%	(95% CI)		%	(95% CI)
Site A
1	5·0	(0·1–24·9)	60·0	(26·2–87·9)	30/388 (7·7)	7·6	(4·5–12·5)
2	25·0	(8·7–49·1)	80·0	(44·4–97·5)	42/396 (10·6)	10·4	(6·7–15·7)
3	0·0	n.a.	n.s.	n.s.	7/390 (1·8)	1·9	(0·7–5·4)
4	85·0	(62·1–96·8)	60·0	(26·2–87·8)	46/382 (12·0)	12·1	(7·9–18·3)
5	5·0	(0·1–24·9)	20·0	(2·5–55·6)	16/386 (4·1)	4·7	(2·5–8·6)
6	5·0	(0·1–24·9)	10·0	(2·5–44·5)	6/396 (1·5)	1·9	(0·7–5·0)
Site B
1	10·0	(1·2–31·7)	10·0	(0·25–44·5)	12/383 (3·1)	3·3	(1·5–7·1)
2	10·0	(1·2–31·7)	100·0	(69·2–100)	156/354 (44·1)	43·1	(35·7–50·9)
3	0·0	n.a.	20·0	(2·5–55·6)	4/379 (1·1)	1·5	(0·50–4·5)
4	30·0	(11·9–54·3)	100·0	69·2–100)	57/339 (16·8)	16·4	(11·3–23·0)
5	5·0	(0·1–24·9)	0·0	n.a.	2/362 (0·6)	1·1	(0·3–4·0)
6	0·0	n.a.	0·0	n.a.	16/386 (4·1)	4·2	(2·1–8·3)
Site C
1	0·0	n.a.	0·0	n.a.	1/387 (0·3)	0·6	(0·1–3·0)
2	0·0	n.a.	80·0	(44·4–97·5)	24/393 (6·1)	5·7	(3·2–10·1)
3	0·0	n.a.	0·0	n.a.	6/390 (1·5)	1·6	(0·6–4·6)
4	15·0	(3·2–37·9)	60·0	(26·2–87·8)	18/371 (4·9)	4·5	(2·4–8·8)
5	5·0	(0·1–24·9)	10·0	(2·5–55·6)	0/376 (0·0)	0·0	n.a.
6	0·0	n.a.	10·0	(2·5–44·5)	10/378 (2·6)	2·5	(1·0–6·1)

n.s., Not sampled; n.a., not applicable.

^*Total of 20 environmental samples per cohort.

^†Total of 10 pooled samples per cohort.

^‡Adjusted apparent prevalence accounting for clustering.