An atypical weakly haemolytic strain of Brachyspira hyodysenteriae is avirulent and can be used to protect pigs from developing swine dysentery

Table 7 Faecal shedding of B. hyodysenteriae by pigs in experiment 3 during the challenge period, as detected by culture on selective media

Group number	Pig number	Culture results (days after first day of first challenge with the virulent strains)^a																											Median
Group number	Pig number	7	10	14	17	21	24	28	31	35	38	41	45	48	51	55	58	61	65	68	71	75	78	81	85	88	91	95	Median
A	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	3	0
	2	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	3	1^c	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	4	1^c	1^c	1^c	1^c	0	1^c	1^c	1^c	1^c	1^c	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	5	1	1^c	1^c	0	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	6	0	1^c	1^c	1^c	0	0	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	7	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	8	1^c	1^c	1^c	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	9	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	10	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	11	1^c	1^c	1^c	0	1^c	0	0	0	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
	12	1^c	0	1^c	1^c	1^c	1^c	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0
Median^b		1*	1*	1	0	0	0	0	0*	0*	0*	0*	0**	0**	0**	0**	0**	0**	0**	0**	0**	0**	0**	0**	0	0	0	0	0**
B	13	0	0	0	0	0	0	0	2	2	2	2	2	2	2	2	2	2	3	5	5	5	5	5	Dead				2
	14	0	0	3	4	4	4	4	3	3	4	5	5	5	5	5	5	5	5	Dead									4
	15	0	0	0	0	0	0	0	2	2	2	2	3	3	4	4	5	5	5	5	5	5	5	5	Dead				3
	16	0	0	0	0	0	0	0	0	0	0	0	3	3	3	2	4	5	5	5	5	5	5	5	Dead				2
	17	0	0	0	0	0	2	2	2	2	2	2	2	2	2	3	1	1	1	5	5	5	5	5	dead				2
	18	0	0	0	0	3	3	3	3	3	4	5	5	5	5	5	5	5	5	5	5	Dead							4.5
	19	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	Dead*				0
	20	0	0	0	0	0	1	2	2	2	2	1	1	1	0	0	0	0	0	0	0	1	1	1	Dead				0
	21	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	Dead*				0
	22	0	0	0	0	0	0	2	2	2	1	1	2	1	1	2	2	1	1	1	3	3	4	5	Dead				1
	23	0	0	0	0	0	0	0	0	0	0	0	4	5	5	5	5	5	5	5	5	Dead							0
	24	0	0	3	3	3	3	3	3	4	4	4	5	5	5	5	5	5	5	Dead									4
Median^b		0*	0*	0	0	0	0	1	2*	2*	2*	1.5*	2.5**	2.5**	2.5**	2.5**	3**	3.5**	4**	5**	5**	4**	4.5**	5**					2**

Pigs in group A had been exposed to MU1, and subsequently they and the pigs in group B which had not been exposed to MU1 were challenged with a cocktail of five virulent field strains of B. hyodysenteriae. Both groups were challenged with the cocktail again after 32 days. Surviving pigs in group A were killed 100 days following challenge with the cocktail, whilst those in group B were killed 85 days pc.
Dead—indicates pigs developed dysentery and were removed for pm.
Dead*—indicates 2 pigs unexposed to MU1 that were healthy and were killed after 85 days (end of experiment for group B).
^aCulture score: 1 to 5, extent of growth on selective agar plates; 0, no growth. Days marked in italics are after the second inoculation with the cocktail, which occurred 32 days after the first inoculation with the cocktail.
^bMedians for the values in groups A and B that are significantly different in a Mann–Whitney test are marked with asterisks (* p < 0.05; ** p < 0.01).
^cGrowth of weakly haemolytic B. hyodysenteriae (MU1). All others were strongly haemolytic.

ISSN: 1297-9716