In situ localization of LUC activity and detection of viral replication in carp periodontal pharyngeal mucosa. Carp weighing 100 g were fed with food pellets contaminated with the CyHV-3 LUC strain. At 2 dpi, carp were anesthetized, injected with luciferine, and euthanized immediately before dissection of the oropharyngeal cavity. Dissected fish were analysed for ex vivo bioluminescence (A). A fragment of periodontal pharyngeal mucosa emitting bioluminescence was harvested and processed for histological (B) and electron microscopy analysis (C and D). Panel C shows low magnification of the epithelium. Panel D shows one representative infected epithelial cell at higher magnification.