Systemic megalocytivirus infection in three-spined stickleback Gasterosteus aculeatus

Iridoviruses have been reported from a wide range of freshwater and marine fish species worldwide and in recent years megalocytiviruses (family Iridoviridae) have emerged as important fish pathogens affecting commercially important species. The present case describes a systemic megalocytivirus infection in a three-spined stickleback Gasterosteus aculeatus L. Histology revealed the presence of numerous cytomegalic cells in several locations throughout the body. Transmission electron microscopy (TEM) revealed the presence of high numbers of viral particles, with a morphology compatible with an iridovirus, throughout the cytoplasm of the affected cells. The histopathological features and the TEM observations are consistent with a megalocytivirus infection.