Can selection for resistance to OsHV-1 infection modify susceptibility to Vibrio aestuarianus infection in Crassostrea gigas? First insights from experimental challenges using primary and successive exposures

Table 1 Summary of the trials and sets to evaluate OsHV-1 and V. aestuarianus susceptibility.

Trial	1	2	3	3	3	3	3	4	4
Set			1	2	3	4	5^a	1^b	2^c
Pathogen	OsHV-1	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus	Vibrio aestuarianus
Infection protocol	Cohabitation	Injection	Cohabitation	Cohabitation	Cohabitation	Cohabitation	Cohabitation	Cohabitation	Cohabitation
Number of exposure	1st infection	1st infection	1st infection	1st infection	1st infection	1st infection	1st infection	2nd infection	3rd infection
Date of challenge	Apr 2013	Jan 2013	Feb 2013	Mar 2013	Mar 2013	May 2014	Nov 2014	May 2014	Nov 2014
Age (months)	13	10	11	12	13	26	32	26	32
Individual weight (g)	22	22	22	22	22	120	100	100	170
Stage	Juvenile	Juvenile	Juvenile	Juvenile	Juvenile	Adult	Adult	Adult	Adult
Number of tanks^f	12	48	3	3	8	2	2	1	1
Tank volume (L)	5	5	150	150	10	150	150	150	150
Lines tank⁻¹	1	1	4	4	1	4	4	4	3^d
Oysters line-1 tank⁻¹	10	10	25	25	15–20	24–32	28–33	1–88^e	1–30^e
OsHV-1 detection in moribunds	Yes	No	No	No	No	No	No	No	No
V. aestuarianus detection in moribunds	No	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

For all trials, two unselected and control lines (AC and BC) and two lines selected for their higher resistance to OsHV-1 (AS and BS) were evaluated under controlled conditions
^aOysters used were survivors from field testing
^bOysters used were survivors from sets 1 to 3 of trial 3
^cOysters used were survivors from set 1 of trial 4
^dOne of the control line had 100% mortality before the trial
^eSelected lines had at least 28 and 12 oysters in sets 4 and 5, respectively, whereas the control lines had less than 5 oysters
^fThe number indicated is without the control tanks

ISSN: 1297-9716