A survey to determine the presence and distribution of largemouth bass virus in wild freshwater bass in New York State

During 2004 and 2005 a survey was conducted to investigate the presence and geographic distribution of largemouth bass virus (LMBV) in New York State. This iridovirus is widely distributed across the eastern United States; however, it had not previously been reported in New York State. Two hundred and eighty-three wild largemouth bass Micropterus salmoides and 8 smallmouth bass M. dolomieu were collected from 37 locations across the state. No clinical signs of LMBV or mortalities attributable to the virus were observed in the fish collected. Using a quantitative polymerase chain reaction (QPCR) method, we detected LMBV in 28 fish from 13 locations. Viral cytopathic effect in cell culture was observed in 5 fish from 3 locations. The virus isolated from cell culture was confirmed to be LMBV by an independent PCR method. Statistical analysis of the largemouth bass samples collected during 2005 revealed a wide difference in prevalence between the QPCR results and the cell culture results. Analysis of possible predictors, including age, sex, and month collected, showed no significant associations with the QPCR results. This survey confirms the presence and wide distribution of a potentially pathogenic form of LMBV in multiple water systems across New York State.     

The Lethal Dose of Largemouth Bass Virus in Juvenile Largemouth Bass and the Comparative Susceptibility of Striped Bass

Abstract

Largemouth bass virus (LMBV) is an iridovirus that was isolated from wild adult largemouth bass Micropterus salmoides in the southeastern United States in 1994. Although originally isolated from moribund wild fish, its virulence to juvenile largemouth bass is uncertain. To help clarify this point, two LMBV titrations were made in juvenile largemouth bass. Titers of LMBV in fathead minnow cells were 10^4.8 and 10^5.8 tissue culture infectious doses—50% cytopathic endpoint (TCID50) per milliliter, respectively. Tenfold serial dilutions of LMBV employed in each cell culture titration, injected intraperitoneally (0.1 mL/fish) into largemouth bass produced calculated lethal dose—50% mortality endpoints (LD50s) of 282 (10^2.45) and 288 (10^2.46) infectious doses in two consecutive infectivity trials. Virus yield of assayed infected fish averaged 10^8.5 TCID50/g and 10^7.7 TCID50/g in viscera of moribund and dead fish in the two trials and 10^6.5 TCID50/g in surviving exposed fish 14 d after infection. In a second experiment, largemouth bass had 100% mortality 5 d after injection while virus immersed fish had a significantly (P ≤ 0.005) lower mortality of 17% at 14 d. Similarly treated juvenile striped bass Morone saxatilis suffered 63% mortality after injection and significantly (P ≤ 0.005) lower mortality of 10% after immersion. In a third study of 25 d, 100% of injected largemouth bass died by 5 d after injection, and all of them were virus-positive. Injected striped bass had a significantly (P ≤ 0.005) lower mortality of 24%; all three fish were virus-positive initially, two fish were virus-positive at 18 d, and none were positive at 25 d. Juvenile largemouth bass were highly susceptible to LMBV injection and striped bass were moderately susceptible, but both species were only mildly susceptible when exposed by immersion.     

Movement behaviour of largemouth bass Micropterus salmoides in a South African impoundment

The objectives of this study were to describe movements and area use patterns of largemouth bass Micropterus salmoides in relation to abiotic factors (water temperature, river inflow and water level). The study was conducted in the Kubusi arm of Wriggleswade Dam, Eastern Cape, South Africa where nine largemouth bass (310–385?mm FL) were surgically implanted with individually coded acoustic transmitters and monitored for nine months (May 2010 to January 2011) using an array of five moored acoustic data-logging receivers. The daily position occupied by largemouth bass was significantly affected by water temperature (P<0.001) and river inflow (P<0.001), whereas water level had no effect. Largemouth bass spent little or no time in the shallow river inlet areas when water temperature was <12.5 °C, but as water temperature increased, their utilisation of shallow areas increased significantly. The results from this study demonstrate the importance of environmental factors, particularly water temperature, on the movement of largemouth bass.     

Computed tomography in the diagnosis of canine hyperadrenocorticism not suppressible by dexamethasone

Computed tomography (CT) was performed in 10 dogs with hyperadrenocorticism not suppressible by dexamethasone. In 6 of these dogs, a unilateral adrenal mass was found on CT images. Specimens of the masses were obtained via retroperitoneal laparotomy; histologic examination revealed 4 carcinomas, 1 adenoma, and 1 nodular hyperplasia. In the 4 other dogs, CT revealed symmetric bilateral adrenal gland enlargement. In 2 of these dogs, contrast-enhanced CT revealed a mass in the pituitary fossa, which could be identified at necropsy as a pituitary tumor. The other 2 dogs were successfully treated with mitotane.     

大口黑鲈虹彩病毒病研究进展

大口黑鲈虹彩病毒(LMBV;又称SCRV)引起的病毒病是迄今为止国内外大口黑鲈病害研究报道最多的病毒性疾病之一.在大口黑鲈原产地美国,LMBV广泛的感染性和致病性引起科研人员和养殖人员的高度关注.论文综述了大口黑鲈虹彩病毒病的来源、地理分布、传播途径、致病性及防控措施等方面的研究进展,并对该病的防控进行了展望,对于国内...     

Isolation of Acholeplasma laidlawii from Centrarchids in a Central Florida Lake

Abstract

In 1991, the poor physical condition of largemouth bass Micropterus salmoides from Lake Harris, Florida, was associated with the decline of the lake's fishery. The swim bladders of emaciated bass had mild inflammation and ecchymotic hemorrhages. A mycoplasma-like organism isolated from swim bladders was initially believed to be the causative agent. The organism was later identified as Acholeplasma laidlawii by using a fluorescent antibody procedure and was demonstrated to be nonpathogenic. Parenteral injection of the organism into healthy largemouth bass fingerlings produced no signs of disease or difference in growth rate compared with control fish during a 16-month period. Field studies resulted in isolation of A. laidlawii from black crappies Pomoxis nigromaculatus, bluegills Lepomis macrochirus, and redear sunfish L. microlophus, but not from noncentrarchids in Lake Harris or from any fish species in a control fishery (Lake Holly, Florida). The absence of organisms in all emaciated bass, our inability to reproduce the disease, and isolation of the organism from seemingly healthy fish suggest this organism was not pathogenic.     

Laboratory transmission of the monogenean Acolpenteron ureteroecetes infecting the posterior kidneys of largemouth bass: time course and pathology

Acolpenteron ureteroecetes infections in the kidneys of largemouth bass Micropterus salmoides have been reported, but the time course of infection and progression of pathology in experimentally infected fish remain unknown. We exposed 299 naive juvenile largemouth bass at 19.8 degrees C to A. ureteroecetes-infected largemouth bass via recirculating water without direct contact. For 7 months, prevalence and density were determined monthly in squashes of posterior kidney (20 exposed fish, 20 nonexposed fish), and histopathology was assessed in 5 fish from each group. Prevalence increased steadily from months 1 (5%) to 4 (85%), thereafter remaining relatively stable. Mean density of infection doubled monthly (month 1, 0.1 individuals/2 cm2 squash; month 7, 15.1 individuals/2 cm2 squash). Eggs were first observed at month 3, and mean density increased markedly from month 4 to month 5 (2.9-15.3 eggs/2 cm2 squash). Histopathology showed damage in renal collecting ducts that got progressively worse between 5 and 7 months. The infected ducts were dilated, had a hyperplastic epithelium, and were surrounded by chronic inflammation, including eosinophilic granular cells and varying degrees of fibrosis. Eggs within granulomas were present in the interstitium; this response is newly reported. The infection system developed in this study provides a reproducible and consistent source of infected individuals that will facilitate further study of the parasite and potential treatments.     

Quantitative polymerase chain reaction assay for largemouth bass virus

The use of quantitative polymerase chain reaction (QPCR) to test for largemouth bass virus (LMBV) was evaluated during a challenge experiment in which largemouth bass Micropterus salmoides were immersed in the type strain of LMBV. The real-time PCR and cell culture methods were both used to measure LMBV present in the inoculum. Additional samples tested by QPCR included gill, gonad, kidney, liver, mucus, spleen, and swim bladder. A plasmid clone containing a 248-base pair (bp) fragment of the major capsid protein gene (MCP*) was serially diluted and used as a standard to quantify the number of LMBV DNA copies present in the samples tested. A 62-bp fragment of DNA located in MCP* was amplified in the real-time PCR assay. This work has demonstrated the value of the QPCR assay in LMBV surveys.     

Mineralized,obstructive cardiac myxoma with chondroid differentiation in a cocker spaniel

A 12-year-old castrated male cocker spaniel dog was referred for evaluation of signs consistent with right-sided heart failure. Thoracic radiography revealed mineralization in the region of the right atrium. Echocardiography identified a mass partially filling the right atrium and right ventricle and obstructing flow through the right heart. These findings were confirmed at necropsy and histopathologic features were consistent with myxoma with chondroid differentiation.     

Vaccine-associated rhabdomyosarcoma with spinal epidural invasion and pulmonary metastasis in a cat

A 7-year-old, female, domestic medium-haired cat had a recurrent deep dermal mass in the interscapular region after initial surgical removal 3 months earlier. The cat had received a killed rabies vaccine and a five-in-one vaccine in the same area about 2 months prior to the first surgery. The relapsed mass was diagnosed as vaccine-associated sarcoma. The cat was euthanized 2 months later because of hind limb paralysis. At necropsy, multiple, poorly demarcated, nodular masses were seen in the muscles around the shoulders, neck, and thoracic vertebrae. Pulmonary metastasis and spinal epidural invasion at T1-T3 with regional cord compression and malacia were observed. Microscopically, the masses consisted of interwoven bundles of spindle cells with prominent multinucleated giant cell formation. The neoplastic cells stained strongly positive for myoglobin, and moderately but variably positive for vimentin, desmin, and alpha- smooth muscle actin. Phosphotungstic acid-hematoxylin staining revealed cytoplasmic striations in scattered tumor cells. The tumor was considered a vaccine-associated rhabdomyosarcoma.     

Survival of Largemouth Bass Iridovirus in Frozen Fish

Abstract

Juvenile largemouth bass Micropterus salmoides were infected with largemouth bass iridovirus by injection and frozen at ?10°C, and the visceral organs and tissues (liver, kidney, spleen, gonads, swim bladder, and muscle) of individual fish were periodically assayed for virus for 155 d postfreezing. The virus was isolated from 35 of 39 (89.7%) of the frozen fish. However, virus loss occurred more rapidly in fish that were dead when frozen than in fish that were alive when frozen. Overall, largemouth bass iridovirus was stable in frozen tissue when the fish were fresh upon freezing.     

Quantitative Polymerase Chain Reaction Assay for Largemouth Bass Virus

Abstract

The use of quantitative polymerase chain reaction (QPCR) to test for largemouth bass virus (LMBV) was evaluated during a challenge experiment in which largemouth bass Micropterus salmoides were immersed in the type strain of LMBV. The real-time PCR and cell culture methods were both used to measure LMBV present in the inoculum. Additional samples tested by QPCR included gill, gonad, kidney, liver, mucus, spleen, and swim bladder. A plasmid clone containing a 248-base pair (bp) fragment of the major capsid protein gene (MCP*) was serially diluted and used as a standard to quantify the number of LMBV DNA copies present in the samples tested. A 62-bp fragment of DNA located in MCP* was amplified in the real-time PCR assay. This work has demonstrated the value of the QPCR assay in LMBV surveys.     

Pericardial mesothelioma in a Bengal tiger (Panthera tigris).

A 17-year-old Bengal tiger (Panthera tigris) presented with dyspnea and tachypnea. Radiographs revealed severe pleural and pericardial effusion, but no obvious mass. During attempts to remove the fluid under anesthesia, the cat developed cardiac tamponade and died. At necropsy, a nodular mass was found at the heart base and was identified as a pericardial mesothelioma. This is the first report of this tumor in any large cat.     

Abdominal fat necrosis in a pygmy goat associated with fescue toxicosis.

Abdominal fat necrosis was diagnosed in an 11-year-old female pygmy goat with a 10-day history of lethargy, anorexia, and progressive abdominal distension. Gross necropsy findings revealed multiple firm, dark yellow, nodular masses of fat throughout the abdominal cavity, which compressed several abdominal organs including the rumen, small intestine, spiral colon, and gall bladder. Histologically, multiple to coalescing adipocyte necrosis, saponification, and infiltration with variable numbers of macrophages, lymphocytes, and plasma cells was observed. Fat necrosis in this case was attributed to tall fescue toxicity based on the presence of high levels of endophyte (Neotyphodium coenophialum)-infected fescue identified in the goat's pasture. This is the first known report of abdominal fat necrosis in a goat and demonstrates the fat necrosis syndrome of fescue toxicosis in ruminants.     

Chronic endometritis in an Asian elephant (Elephas maximus).

A 48-yr-old female Asian elephant with a history of pododermatitis developed recurrent hematuria beginning in 2002. Transrectal ultrasonography and endoscopic examination in 2004 identified the uterus as the source of hematuria and excluded hemorrhagic cystitis. Treatment with Desloreline implants, antibiotics, and homeopathic drugs led to an improved general condition of the elephant. In July 2005, the elephant was suddenly found dead. During necropsy, the severely enlarged uterus contained about 250 L of purulent fluid, and histopathology revealed ulcerative suppurative endometritis with high numbers of Streptococcus equi ssp. zooepidemicus and Escherichia coli identified on aerobic culture. Additional findings at necropsy included: multifocal severe pododermatitis, uterine leiomyoma, and numerous large calcified areas of abdominal fat necrosis. Microbiologic culture of the pododermatitis lesion revealed the presence of Streptococcus agalactiae, Streptococcus equi ssp. zooepidemicus, Staphylococcus sp., Corynebacterium sp., and Entercoccus sp.     

Cerebellar leptomeningeal carcinomatosis in a dog

Diffuse cerebellar meningeal carcinomatosis secondary to haematogenous dissemination from an anaplastic solid mammary carcinoma was diagnosed in an old German shepherd dog suffering from seizures and rapidly progressing to stupor. A single computed tomography cerebellar scan identified an unusual homogeneous density area that was considered to be associated with a vascular disorder, in the absence of space-occupying lesions. At necropsy, nodular masses were observed in the mammary gland, lungs, tracheobronchial lymph nodes and adrenals. Cerebellar leptomeninges were affected by diffuse blood effusion. Histology showed a solid mammary tumour, characterised by anaplastic cells with a cytoplasmic keratin-positive and vimentin-negative immunoreaction. The tumour had spread to the lungs, tracheobronchial lymph nodes and adrenals. Cerebellar leptomeninges were diffusely infiltrated by the cytokeratin-positive neoplastic cells. Even though computed tomography scan gave no evidence of meningeal carcinomatosis, it was considered that a cerebellar vascular disorder might be present. This was subsequently confirmed by neuropathological investigation and seen to be associated with a cerebellar leptomeningeal carcinomatosis.     

Neuroendocrine tumor in the lung of a captive black spider monkey (Ateles paniscus)

This paper describes a neuroendocrine (NE) tumor of the lung that was observed during the necropsy of a 14-year-old female black spider monkey (Ateles paniscus) with sudden death. Grossly, multifocal firm and coalescing nodular masses were observed in the lung. The histological examination showed the tumor to be an typical NE tumor with polygonal cells grouped in small solid aggregates, with regularly sized, spherical, centrally placed nuclei with modest, lightly granular cytoplasm suspended in a fibrovascular stroma. The immunohistochemical examination revealed the tumor to be positive for cytokeratin, chromogranin A and synaptophysin, and negative for CD56. To the best of our knowledge, this is the first report of NE tumor in the lung of the black spider monkey.     

Generalized nodular dermatofibrosis in the absence of renal neoplasia in an Australian Cattle Dog

A 13-year-old, spayed, female Australian Cattle Dog had at least a 10-year history of numerous subcutaneous nodules for which fine-needle aspiration and cytologic evaluation were nondiagnostic. Abdominal ultrasound 3.5 months before necropsy detected a small left kidney but no cysts or neoplasms. At gross necropsy, innumerable, firm, round to oval, white, 0.25 to 2 cm masses were detected throughout the subcutaneous tissues of the axial and appendicular skeleton, epimysium of numerous muscles, and parietal peritoneum of the lateral abdominal body wall. The left kidney was approximately half the size of the right, and there was severe bilateral renal medullary (papillary) necrosis. Histologically, the subcutaneous nodules were well-demarcated masses of mature, hypocellular collagen that were consistent with previous reports of nodular dermatofibrosis and renal cystadenomas or cystadenocarcinomas. In addition to diffuse acute medullary necrosis, both kidneys were affected by severe chronic lymphoplasmacytic interstitial nephritis. This is the first known report of nodular dermatofibrosis in a dog without renal cysts, cystadenoma, or cystadenocarcinoma.     

Effects of Practices Related to Catch-and-Release Angling on Mortality and Viral Transmission in Juvenile Largemouth Bass Infected with Largemouth Bass Virus

Abstract

Largemouth bass virus (LMBV; family Iridoviridae) has recently emerged as a causative agent in fish kills of largemouth bass Micropterus salmoides. Little is known about how the virus is transmitted or what factors predispose fish to mortality subsequent to infection. Concern has nevertheless arisen that activities related to recreational angling may affect transmission dynamics and may alter the susceptibility of infected fish to clinical disease. This study examined the separate effects of two angling-related factors on the susceptibility of juvenile largemouth bass to mortality from LMBV infection and on the transmission of LMBV from infected to uninfected fish. The first factor was hook-and-line angling. Infected fish that underwent a simulated angling treatment did not experience higher mortality or have higher viral loads in their tissues than those that were not angled. The second factor was direct contact between infected and uninfected fish, as would occur in live wells and holding tanks. The LMBV was transmitted from infected to uninfected fish through water, even when direct contact was prevented. Transmission of LMBV between infected and uninfected fish separated by a fenestrated barrier was nearly as efficient as LMBV transmission between infected and uninfected fish that were allowed direct contact. These results imply that angling itself may have only minimal effects on the survival of largemouth bass infected with LMBV but that angling-related practices that place infected and uninfected fish together in a limited water volume may facilitate viral transmission. Partitioning or cooling of live wells and holding tanks, as well as limiting their use, could reduce LMBV-associated mortality and viral transmission.     

Isolation and Identification of Viruses from Adult Largemouth Bass during a 1997–1998 Survey in the Southeastern United States

Abstract

A total of 452 largemouth bass Micropterus salmoides (mostly adults) from 78 reservoirs, lakes, rivers, and state fish hatcheries in eight states of the southeastern USA were surveyed for largemouth bass virus (LMBV) between August 1997 and November 1998. Virus was isolated from ostensibly healthy electrofished largemouth bass from six reservoirs on four different river systems—Lakes Jordan (Coosa River) and Wilson (Tennessee River) in Alabama; Lakes Walter F. George and Oliver (Chattahoochee River), Lake Blackshear (Flint River), and Lake Allatoona (Coosa River) in Georgia—and from moribund fish from Lake Walter F. George and Lake Greenwood (Santee River) in South Carolina. Fish samples from 71 locations in Alabama, Florida, Georgia, Kentucky, Louisiana, Missouri, South Carolina and Virginia showed no evidence of virus infection. Sequence analysis of the major capsid protein gene showed that virus isolates from Lakes Walter F. George, Jordan, Blackshear, and Allatoona were identical to the original LMBV isolate from Santee–Cooper Reservoir. Largemouth bass virus is a member of the genus Ranavirus within the family Iridoviridae and is nearly identical to doctor fish virus (DFV-16) and guppy virus (GV6), two fish viruses from Southeast Asia.