Table 1. Pig farms included in this study.

Pig farm	Participants	No. of sows	No. of weaners	No. of finishers
Pig farm workers
A	1–4	1,000	1,300	0
B	5–8	800	3,000	200
C	9–12	650	2,300	5,740
D	13–16	885	3,304	2,400
Volunteers and pigs
E	8 volunteers	0	2,400	450
	4 pigs