FIG 2.

ESV infection causes high mortality rates in larval and adult zebrafish. (A) Groups of AB zebrafish larvae (n > 11) at 6 days postfertilization (dpf) were infected by bath immersion with increasing doses of semipurified ESV obtained by ultracentrifugation of crude viral stocks through a 45% sucrose cushion as indicated, and cumulative mortality was recorded daily up to 8 dpi. Shown is one representative experiment of three. (B) Groups of adult AB zebrafish (mock, n = 28; ESV, n = 38) were infected by bath immersion with a single dose of 2 × 10⁶ PFU/ml of semipurified ESV, and cumulative mortality was recorded daily up to 17 dpi. Shown is one representative experiment of three. (C) Transmission electron micrograph of ultrathin sections of glutaraldehyde-fixed and Epon-embedded ESV-infected larva at 2 dpi. The inset shows a detail of budding viruses from a different section. (D) Hematoxylin and eosin (H&E)-stained section of an adult zebrafish kidney corresponding to mock-infected (a) or ESV-infected (b) animals at 48 h p.i. Arrows indicate nuclear chromatin margination, necrosis, and vacuolation in segments of the renal tubular epithelium. Scale bars are shown in panels C and D.