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. KEY WORDS: Iridoviridae · Megalocytivirus · Infectious spleen and kidney necrosis virus · Aquaculture · Ornamental fish Resale or republication not permitted without written consent of the publisherDis Aquat Org 119: [253][254][255][256][257][258] 2016 Although tilapia are considered relatively resistant to disease, they are susceptible to common aquatic pathogens (e.g. viruses, bacteria, fungi, water molds, parasites) when reared intensively. The primary microbial pathogens affecting cultivated tilapia include Gram-negative bacteria (Aeromonas hydrophila, Flavobacterium columnare, and Francisella noatunensis), Gram-positive bacteria (Streptococcus spp.), and water molds such as members of the family Saprolegniaceae (e.g. Achyla and Saprolgenia spp.; Plumb & Hanson 2010). Despite the global culture of tilapia, few viruses have been described from tilapia, and none has proven to be a serious threat to the industry (El-Sayed 2006).The first RNA virus discovered in tilapia was an aquabirnavirus isolated from apparently healthy Mozambique tilapia O. mossambicus cultured in Lukang, Taiwan (Hedrick et al. 1983). In 2007, a betanodavirus was detected by RT-PCR in Nile tilapia larvae following a mass mortality event at a western European fish farm (Bigarré et al. 2009), andEyngor et al. (2014) isolated a novel RNA virus (tilapia lake virus) from wild tilapia and confirmed its pathogenicity via experimental infection in Nile tilapia.The first DNA viruses discovered in tilapia were iridoviruses. Although the family Iridoviridae is composed of 5 genera, only members of the genera Megalocytivirus, Lymphocystivirus, and Ranavirus infect fish (Zhang & Gui 2015). Paperna (1973) detected lymphocystis virus in tilapine and haplochromine cichlids from the Rift Valley Lakes Kitangiri and Victoria. A severe (100% mortality) epizootic among Mozambique tilapia fry held in an Australian aquatic disease laboratory was tentatively attributed to a ranavirus, Bohle ir...
A series of fungal cases in hatchery-reared juvenile and young adult Siberian sturgeon Acipenser baerii and white sturgeon A. transmontanus occurred at production facilities in Florida and California, USA, respectively. Affected fish exhibited abnormal orientation and/or buoyancy, emaciation, coelomic distension, exophthalmos, cutaneous erythema, and ulcerative skin and eye lesions. Necropsies revealed haemorrhage throughout the coelom, serosanguinous coelomic effusion and organomegaly with nodular or cystic lesions in multiple organs. Fungal hyphae were observed in 27 fish (24 A. baerii and 3 A. transmontanus) via microscopic examination of tissue wet mounts and on slides prepared from colonies grown on culture media. Histopathological examination of these infected tissues revealed extensive infiltration by melanised fungal hyphae that were recovered in culture. Phenotypic characteristics and sequencing of the fungal isolates with the use of the internal transcribed spacer region and 28S rRNA gene confirmed the aetiological agent as Veronaea botryosa. To our knowledge, this is the first documentation of V. botryosa infection in fish, although melanised fungi of the closely related genus Exophiala are well-known pathogens of freshwater and marine fishes.
This study investigates the vomeronasal organ in extant nocturnal strepsirhines as a model for ancestral primates. Cadaveric samples from 10 strepsirhine species, ranging from fetal to adult ages, were studied histologically. Dimensions of structures in the vomeronasal complex, such as the vomeronasal neuroepithelium (VNNE) and vomeronasal cartilage (VNC) were measured in serial sections and selected specimens were studied immunohistochemically to determine physiological aspects of the vomeronasal sensory neurons (VSNs). Osteological features corresponding to vomeronasal structures were studied histologically and related to 3-D CT reconstructions. The VNC consistently rests in a depression on the palatal portion of the maxilla, which we refer to as the vomeronasal groove (VNG). Most age comparisons indicate that in adults VNNE is about twice the length compared with perinatal animals. In VNNE volume, adults are 2-to 3-fold larger compared with perinatal specimens. Across ages, a strong linear relationship exists between VNNE dimensions and body length, mass, and midfacial length. Results indicate that the VNNE of nocturnal strepsirhines is neurogenic postnatally based on GAP43 expression. In addition, based on Olfactory Marker Protein expression, terminally differentiated VSNs are present in the VNNE. Therefore, nocturnal strepsirhines have basic similarities to rodents in growth and maturational characteristics of VSNs. These results indicate that a functional vomeronasal system is likely present in all nocturnal strepsirhines. Finally, given that osteological features such as the VNG
Lernaea species, commonly known as “anchorworms,” are crustacean, copepod parasites that can infect and cause disease and mortality in many types of freshwater fishes, especially wild-caught and pond-raised species. Infestations with Lernaea are most prevalent in the summer months and occur more commonly in stagnant or slow-moving water bodies. This 4-page fact sheet was written by Natalie Steckler and Roy P. E. Yanong and published by the UF Department of Fisheries and Aquatic Sciences, December 2012. http://edis.ifas.ufl.edu/fa185
The short-finned eel ranavirus (SERV) was isolated from short-finned eel imported to Italy from New Zealand. Phylogenomic analyses revealed that SERV is a unique member of the genus Ranavirus, family Iridoviridae, branching at the base of the tree near other fish ranaviruses.
Argulus species (Family: Argulidae), more commonly known as fish lice, are members of a large group of branchiuran parasites that infest and cause disease in fish. The argulids are crustaceans and are related to crabs, lobsters, and shrimp. This 5-page fact sheet was written by Natalie Steckler and Roy P. E. Yanong and published by the UF Department of Fisheries and Aquatic Sciences, November 2012. http://edis.ifas.ufl.edu/fa184
The pike-perch iridovirus (PPIV) was isolated in Finland from apparently healthy pike-perch fingerlings during routine disease surveillance. Our phylogenomic analysis revealed that PPIV is the first fish member of a clade of ranaviruses previously described from European and Chinese amphibians.
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