Figure 5

Poly(I:C) priming efficiency during a naturally occurring disease outbreak. (a) Kaplan–Meier survival curves were generated from spats primed by injection after anesthesia with 10 µg of poly(I:C) per oyster (green line) 1 day before deployment in a coastal lagoon of the Mediterranean sea (Thau Lagoon, France) before a disease outbreak (April 2015). Animals without treatment are represented as non-treated control (black line). Mortalities in groups of 100 oysters were monitored for 119 days after deployment. Different letters next to the graphed lines indicate statistically significant difference among treatment at p-value < 0.0001(log-rank test; n = 100). (b) Kaplan–Meier survival curves were generated from spats primed after anesthesia with poly(I:C) (19 µg.g⁻¹ of oyster) (green lines) or with filtered seawater as a control (FSW, red lines), 126 days (priming A), 99 days (priming B), 71 days (priming C) or 1 day (priming D) before deployment in the Thau Lagoon during a disease outbreak (June 2016). Animals without treatment are represented as non-treated control (black line). Mortalities in groups of 100 oysters were monitored for 30 days after deployment. Different letters next to the graphed lines indicate statistically significant difference among treatment at a-b p-value < 0.0001; b-c p-value < 0.05 (log-rank test, n = 100). (c) OsHV-1 DNA detection on 2016 experiment, by quantitative PCR. Results are expressed as the mean number of DP copies detected per ng of genomic DNA extracted from whole spat pools at 9 and 14 days post immersion. The effect of priming on OsHV-1 μvar loads was determined using Kruskal-Wallis test. Statistical differences represent an increase of OsHV-1 loads compared to the loads at the beginning of the experiment (T0). Significant differences between treatments were performed using Mann-Whitney test (*p-value < 0.1; **p-value < 0.05; ***p-value < 0.01- n = 12 pools of 3 oysters for poly(I:C) and FSW treated oysters and n = 3 pools of 3 oysters for non-treated oysters).