FIG. 7.

Attenuation and protection of rSDV in trout. (A) Juvenile trout (n = 100; mean weight, 0.5 g) were infected by immersion in a water bath with 5 × 10⁴ PFU/ml of the wild-type SDV strain B or J (wtSDV-B or wtSDV-J) or with the recombinant SDV (rSDV) or mock infected. Mortalities were recorded every day and are expressed as a percentage of cumulative mortality. d.p.i, days postinfection. (B) Trout infected with rSDV 3 months (left) or 5 months (right) earlier were challenged with the wtSDV-B, and cumulative mortality was recorded 2 months later (months 5 and 7, respectively). Naïve trout are trout infected with the wtSDV-B (positive infection control). Mock-infected trout are trout treated under the same conditions except that cell culture medium was used.