title: Megalocytivirus infection in cultured Nile tilapia Oreochromis niloticus.
abstract: Megalocytiviruses, such as infectious spleen and kidney necrosis virus (ISKNV), induce lethal systemic diseases in both ornamental and food fish species. In this study, we investigated an epizootic affecting Nile tilapia Oreochromis niloticus cultured in the US Midwest. Diseased fish displayed lethargy, gill pallor, and distension of the coelomic cavity due to ascites. Histopathological examination revealed a severe systemic abundance of intravascular megalocytes that were especially prominent in the gills, kidney, spleen, liver, and intestinal submucosa. Transmission electron microscopic examination revealed abundant intracytoplasmic polygonal virions consistent with iridovirus infection. Comparison of the full-length major capsid protein nucleotide sequences from a recent outbreak with a remarkably similar case that occurred at the same facility many years earlier revealed that both epizootics were caused by ISKNV. A comparison of this case with previous reports suggests that ISKNV may represent a greater threat to tilapia aquaculture than previously realized.
authors.affiliation: Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Kuttichantran
authors.initials: K
authors.lastname: Subramaniam
authors.forename: Michael
authors.initials: M
authors.lastname: Gotesman
authors.forename: Charlie E
authors.initials: CE
authors.lastname: Smith
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Steckler
authors.forename: Karen L
authors.initials: KL
authors.lastname: Kelley
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Groff
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Waltzek
mesh_terms: D000818:Animals; D017756:Aquaculture; D023681:Cichlids; D004266:DNA Virus Infections / Q000662:veterinary* / Q000821:virology; D005393:Fish Diseases / Q000821:virology*; D007497:Iridoviridae / Q000302:isolation & purification*