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The channel catfish (Ictalurus punctatus, Rafinesque) ovary (CCO) cell line is the standard cell line used for channel catfish diagnostics. Next‐gen sequencing studies of a virus cultured in the CCO cells revealed mitochondrial sequences matching those of brown bullhead (Ameiurus nebulosus, Lesueur). Therefore, we systematically performed partial cytochrome oxidase 1 gene sequencing of several sources of the CCO cell line and all matched the brown bullhead and not the channel catfish. [ABSTRACT FROM AUTHOR]

The genus Edwardsiella is composed of a diverse group of facultative anaerobic, gram-negative bacteria that can produce disease in a wide variety of hosts, including birds, reptiles, mammals, and fish. Our report describes the isolation and identification of Edwardsiella piscicida associated with chronic mortality events in 2 separate captive largemouth bass (Micropterus salmoides) populations in New York and Florida. Wet-mount biopsies of skin mucus, gill, kidney, and spleen from several affected largemouth bass contained significant numbers of motile bacteria. Histologic examination revealed multifocal areas of necrosis scattered throughout the heart, liver, anterior kidney, posterior kidney, and spleen. Many of the necrotic foci were encapsulated or replaced by discrete granulomas and associated with colonies of gram-negative bacteria. Initial phenotypic and matrix-assisted laser desorption ionization–time of flight mass spectrometric analysis against existing spectral databases of recovered isolates identified these bacteria as Edwardsiella tarda. Subsequent molecular analysis using repetitive sequence mediated and species-specific PCR, as well as 16S rRNA, rpoB, and gyrB sequences, classified these isolates as E. piscicida. As a newly designated taxon, E. piscicida should be considered as a differential for multiorgan necrosis and granulomas in largemouth bass. [ABSTRACT FROM AUTHOR]

Juvenile rainbow trout, Oncorhynchus mykiss, were fed diets containing 0, 0.5, 1.0, and 2.0% of a garlic extract, challenged with a modified 50% lethal dose of Aeromonas salmonicida and monitored for 28 d. There were significant increases in survival of trout fed 0.5 and 1.0% garlic extract as compared to the control and 2.0% garlic extract groups. A target animal safety study was performed at varying increments using the target dose of 0.5% garlic extract at 0× (0% garlic extract), 1× (0.5% garlic extract), 3× (1.5% garlic extract), and 5× (2.5% garlic extract) for 3× (6 wk) the duration of the original study. There was a significant increase in the level of circulating lymphocytes and a significant decrease in the level of circulating monocytes. The latter correlated to an increased level of pigment-containing macrophage centers within the renal tissue as garlic extract dosing increased, denoting a potential deleterious inflammatory effect as macrophage infiltration became severe at the highest dose. These studies suggest that feeding low-dose (0.5% or 1.0%) garlic extract improves survivability in rainbow trout when challenged with A. salmonicida and appears safe; however, higher levels do not appear to be effective and may cause deleterious effects on health. [ABSTRACT FROM AUTHOR]

The emergence of a new sublineage of viral hemorrhagic septicemia virus ( VHSV) within the Laurentian Great Lakes has caused concern for aquaculture in the United States. Because of the occurrence of VHSV in a new geographic location, new host species have been identified and the complete host range has not been determined. This study confirmed the high resistance of rainbow trout, Oncorhynchus mykiss, to VHSV type IVb infection. In addition, the experimental susceptibility of hybrid striped bass, Morone chrysops ♂ × Morone saxatilis ♀, to VHSV type IVb infection was examined but determined to be highly dependent on age of fish and exposure temperature. No mortality was observed in adult fish infected via intraperitoneal ( IP) injection at 15 C, whereas yearling fish infected via IP injection under the same conditions experienced 20.8% mortality. Among yearling fish infected via IP injection, mortality increased to 100% when exposure to VHSV occurred at 10 C. An LD50 for yearling hybrid striped bass exposed to VHSV at 10 C by IP injection was determined to be 1.4 × 104 pfu ( SE = 2.1). Thus, at 10 C, yearling hybrid striped bass experience a high mortality when exposed to VHSV IVb by IP injection. [ABSTRACT FROM AUTHOR]

Nonlethal sampling is becoming a common method to diagnose fish diseases, especially with the availability of molecular testing. Viral hemorrhagic septicemia virus (VHSV) is a viral pathogen of finfish distributed worldwide. Although VHSV has been known to occur in some parts of the world for decades, a new genotype, IVb, recently emerged in the Laurentian Great Lakes of northeastern North America. Golden shiners (Notemigonus crysoleucas; Mitchill, 1814) and fathead minnows (Pimephales promelas; Rafinesque, 1820) were exposed to VHSV-IVb doses between 102 and 106 plaque forming units per fish by intraperitoneal injection at 10°C. Both species experienced significant mortality after exposure, ranging from 38% to 52% in golden shiners and from 35% to 95% in fathead minnows. In golden shiners, a fin or gill sample was somewhat less sensitive at detecting VHSV-IVb by quantitative reverse transcription polymerase chain reaction (qRT-PCR) than a pooled organ sample (consisting of liver, anterior and posterior kidney, spleen, and heart), however the relative sensitivity increased when a fin and gill sample were tested in parallel. In fathead minnows, a fin or gill sample tested alone or in parallel was relatively more sensitive than a pooled organ sample by qRT-PCR. Specificity was 100% for all sample types in both species. The results suggest that fin and gill biopsies are useful tools to test for VHSV in live fish. [ABSTRACT FROM PUBLISHER]

Two experiments were performed to determine the persistence of viral hemorrhagic septicemia virus (VHSV) genotype IVb on WalleyeSander vitreuseggs. Fertilized Walleye eggs were exposed for 30 min to 105plaque-forming units/mL VHSV genotype IVb, and control eggs were exposed to phosphate-buffered saline. In the first experiment, the eggs were treated with 0 and 50 mg/L iodophor and incubated at 12±1°C until the first fry emerged. In the second experiment, a treatment of 100 mg/L iodophor was also tested. Periodic samples were taken during embryo development and tested for VHSV by viral isolation and quantitative reverse-transcription polymerase chain reaction (qRT-PCR). The effect of tannic acid, an inhibitor of qRT-PCR testing, was evaluated in the second experiment. In both experiments no virus was detected in any control eggs by either test. In the first experiment, virus was isolated in 0-mg/L iodophor-treated eggs up to 3 d postinfection (DPI). Virus was also isolated in the 50-mg/L iodophor-treated group at 1 DPI. Testing by qRT-PCR detected viral RNA at all time points throughout the first experiment. In the second experiment, no VHSV was isolated after the initial 0-DPI sample. Viral RNA was again detected at all time points, including samples collected at the end of the experiment. Inhibition was found in 34 of 36 samples at 0 DPI and 21 of 36 samples at 1 DPI. The number of inhibited samples decreased over time, but virus was still detected in three samples at 24 DPI. These experiments show that VHSV persists on Walleye eggs for longer than was previously known. At early time points VHSV was still detected despite disinfection, and viral RNA was detected at all time points; however, it is unknown whether the virus detected by this qRT-PCR is viable. These experiments reinforce the need for careful disinfection of eggs. Received November 28, 2011; accepted February 26, 2012 [ABSTRACT FROM PUBLISHER]

The article investigates the effectiveness of detecting cyprinid herpesvirus 3 (CyHV3) in common carp, Cyprinus carpio carpio, with the use of molecular virus surveillance methods in the Great Lakes. The gill and a pooled internal organ sample were tested for CyHV3 using quantitative polymerase chain reaction (PCR). Virus was detected in 18 of the 675 carp sampled from nine sites in four lakes. Tissues from these 18 fish were also tested for CyHV3 with the use of the PCR assay.

Viral hemorrhagic septicemia virus (VHSV) is the etiologic agent of a disease of great concern to aquaculture. We performed experimental infections with intraperitoneal VHSV IVb injections at 106 pfu/fish in four species: tiger muskellunge, ♂ Esox lucius×♀ Esox masquinongy; Atlantic salmon, Salmo salar; channel catfish, Ictalurus punctatus; and walleye, Sander vitreus. The fish were thermal shocked concurrent with infection to cause immunosuppression and increase the probability of eliciting disease. Each species was observed for morbidity and mortality and periodic samples taken. Virus was detected using virus isolation and real-time quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Histopathology confirmed lesions in tiger muskellunge and Atlantic salmon, and immunohistochemistry showed virus associated with some lesions. Tiger muskellunge were highly susceptible to VHSV IVb, and high viral levels were detected in exposed fish. A single mortality was observed in exposed Atlantic salmon with a short viral replication period. Channel catfish and walleye were resistant to developing clinical signs of VHS. The results show that these species vary in the development of VHS under these conditions, and qRT-PCR testing enabled virus detection in subclinically affected fish. Basic concordance statistics between the qRT-PCR test results and the virus isolation results were evaluated. [ABSTRACT FROM AUTHOR]

The article discusses research on leiomyosarcoma in a quarantined Atlantic salmon at the North Attleboro National Fish Hatchery in Massachusetts. It describes experimental details performed including administration of drugs to euthanize infected fishes, gross examination of tissues and use of immunohistochemistry to identify smooth muscle actin filaments. It also mentions the development of a polymerase chain reaction assay-specific salmon retrovirus with the use of frozen tissues gathered.

We investigated a newly introduced pathogen in a wild population of smallmouth bass Micropterus dolomieu in the St. Lawrence River to illuminate unknown temporal and demographic prevalence patterns. We used real-time quantitative reverse-transcription polymerase chain reaction to assess viral hemorrhagic septicemia virus (VHSV) genotype IVb (VHSV-IVb) viral N-gene levels. Our objectives were to characterize the distribution and abundance of this newly introduced pathogen within a naive population of economically valuable sport fish through an annual cycle. We also sought to describe VHSV-IVb levels across demographic groups (males and females; adults and subadults). Strong temporal variation in prevalence of VHSV-IVb was evident through the annual cycle; peaks in prevalence corresponded to the smallmouth bass spawning period and a temperature range of 10-14°C. No difference in VHSV-IVb prevalence between male and female smallmouth bass was detected. However, a markedly higher prevalence was observed in subadult fish than in adult fish. Owing to the observed temporal patterns in prevalence, surveillance programs for VHSV-IVb in smallmouth bass should concentrate effort on springtime sampling and should include subadult fish. [ABSTRACT FROM AUTHOR]

Surface de-adhesion and disinfection of eggs at hatcheries are critical steps in successful fry culture; however, little is known about the effects of the combination of these compounds on the efficacy of egg surface disinfection. We examined the effect of tannic acid on detection of viral hemorrhagic septicemia virus (VHSV) type IVb alone and in the presence of iodophor under in vitro conditions. We confirmed that tannic acid inhibits the quantitative reverse-transcriptase polymerase chain reaction assay developed in our laboratory and that it binds to VHSV, reversibly decreasing infectivity. Surprisingly, we also found that when combined with iodophor, tannic acid destroys the ability of either compound to inhibit infectivity. While we still strongly encourage the use of iodophor for its antiviral, bactericidal, and fungicidal properties, our results suggest that when tannic acid is used prior to disinfection with iodophor, it must be very thoroughly rinsed to ensure that it does not interfere with the disinfectant properties of iodophor. [ABSTRACT FROM AUTHOR]

A 5-year-old male telescope goldfish ( Carassius auratus) developed buphthalmia of the left eye. An enucleation was performed and a diagnosis of a neuroectodermal tumor was made on histological examination. Although the fish initially recovered, it was killed 49 days postsurgery due to a severe decline in its condition. On histological evaluation of postmortem tissue samples, it was determined that the fish also had a neuroectodermal tumor of the right eye with local invasion of the brain. On immunohistochemistry, the neoplastic cells were positive for S-100. To the authors’ knowledge, this is the first published case of naturally occurring bilateral intraocular neuroectodermal tumors in a fish. [ABSTRACT FROM AUTHOR]

Adult height is a risk factor in numerous human cancers that involve aberrant receptor tyrosine kinase (RTK) signalling. However, its importance is debated due to conflicting epidemiological studies and the lack of useful in vivo models. In Xiphophorus fishes (Platyfishes/Swordtails), a functional RTK, Xiphophorus melanoma receptor kinase ( Xmrk), serves as the dominant oncogene and has been maintained for several million years despite being deleterious and in an extremely unstable genomic region. Here we show that the Xmrk genotype is positively correlated with standard length in male and female wild caught Xiphophorus cortezi sampled throughout their phylogeographic distribution. Histopathology confirms the occurrence of malignant melanomas in both sexes; however, melanoma incidence was extremely male biased. Furthermore, males collected with malignant melanomas in the field were significantly larger than both Xmrk males collected without melanomas and wildtype ( Xmrk deficient) males. These results not only provide a novel selective mechanism for the persistence of the germline Xmrk oncogene but also create an innovative avenue of melanoma research within the Xiphophorus fishes. Wildlife cancer in natural systems is a growing concern, therefore, future research investigating life history characteristics associated with certain phenotypes and genotypes that predispose an individual to cancer will be fundamental to increasing our understanding of the evolutionary biology of cancer in nature as well as in humans. [ABSTRACT FROM AUTHOR]

Viral hemorrhagic septicemia virus (VHSV) is a rhabdovirus found in fish from oceans of the northern hemisphere and freshwaters of Europe. It has caused extensive losses of cultured and wild fish and has become established in the North American Great Lakes. Large die-offs of wild fish in the Great Lakes due to VHSV have alarmed the public and provoked government attention on the introduction and spread of aquatic animal pathogens in freshwaters. We investigated the relations between VHSV dispersion and shipping and boating activity in the Great Lakes by sampling fish and water at sites that were commercial shipping harbors, recreational boating centers, and open shorelines. Fish and water samples were individually analyzed for VHSV using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and cell culture assays. Of 1,221 fish of 17 species, 55 were VHSV positive with highly varied qRT-PCR titers (1 to 5,950,000 N gene copies). The detections of VHSV in fish and water samples were closely associated and the virus was detected in 21 of 30 sites sampled. The occurrence of VHSV was not related to type of site or shipping related invasion hotspots. Our results indicate that VHSV is widely dispersed in the Great Lakes and is both an enzootic and epizootic pathogen. We demonstrate that pathogen distribution information could be developed quickly and is clearly needed for aquatic ecosystem conservation, management of affected populations, and informed regulation of the worldwide trade of aquatic organisms. [ABSTRACT FROM AUTHOR]

The first isolation of Vibrio vulnificus in southern Taiwan from hybrid tilapia Oreochromis sp. raised in freshwater and brackish water environments is documented in this report. The infection was only found in fish in ponds where the salinity was less than 10 ppt. Tilapia raised in water of higher salinities in the same region were not affected. Grossly visible signs of infection included dark coloration, lethargy, and external hemorrhage and ulceration of the skin. The most prominent internal signs of infection included splenomegaly and severe hemorrhagic lesions in the liver. Septicemia was documented in moribund fish. All bacterial isolates from moribund fish were tested by polymerase chain reaction, using V. vulnificus hemolysin/cytolysin gene-specific primers. Sequence data from the 16S ribosomal RNA gene suggest that these isolates were V. vulnificus. The isolates were indole and mannitol positive, characteristics shared by human clinical isolates and isolates from freshwater European eel, Anguilla anguilla. The isolates from tilapia were unique in that they were negative for ornithine decarboxylase and citrate. [ABSTRACT FROM AUTHOR]

Previous researchers demonstrated that a mortality in fry (called Cayuga syndrome) of Atlantic salmon Salmo salar from Cayuga Lake (New York) was associated with low levels of thiamine. They reduced the mortality of fry by bathing or injecting fry with thiamine. We injected four to six gravid female Atlantic salmon with either physiological saline (PS) or PS plus thiamine (7 mg/kg weight) 14-23 d before eggs were stripped, fertilized, and incubated in individual lots. Chemical analyses showed that eggs from control and treated salmon contained 1.1 and 1.6 nmol thiamine/g, respectively. Thiamine injections had no significant effect on the percentage of eggs that hatched. Between 700 and 800 Celius degree-days postfertilization, control fry (saline) showed signs of Cayuga syndrome and a 45% incidence of mortality; in contrast, mortality was only 1.9% for fry that received thiamine. By 1,078 degree-days postfertilization, mean mortality of control fry was 98.6%, whereas that for thiamine-injected salmon was 2.1%. This study showed that thiamine injections of prespawning female salmon from Cayuga Lake increased thiamine content of their eggs and prevented the Cayuga syndrome and subsequent mortality of fry. Historically, overfishing, pollution, and building of dams and barriers to spawning migration were suggested as possible causes of the decline of the Atlantic salmon in Lake Ontario and Cayuga Lake. Based on our findings and other reports, we suggest another possible contributing cause of the extirpation of landlocked Atlantic salmon in Lake Ontario and some other inland waters of New York: the entrance of alewives Alosa pseudoharengus containing thiaminase, which induced thiamine deficiency in eggs and increased mortality in fry of the predatory salmon. [ABSTRACT FROM AUTHOR]