Experimental transmission of a dermal sarcoma in fingerling walleyes (Stizostedion vitreum vitreum)

Dermal sarcoma is a benign skin tumor of adult walleyes (Stizostedion vitreum vitreum) with a suspected viral etiology. A laboratory study was initiated to determine if the tumor could be experimentally transmitted by inoculating young walleyes with materials prepared from tumors from adult fish. Eighty walleye fingerlings were divided into four groups of 20 fish each. Two groups were inoculated intramuscularly at 4 months of age either with live tumor cells or with cell-free filtrates of sonicated tumor cells. The two other groups were used as controls and were inoculated either with cultured cells from normal walleye fry or with tissue culture media. Neoplasms, similar to the dermal sarcoma affecting adult walleyes, were observed after 4 months only in fingerlings inoculated with cell-free filtrates of sonicated tumor cells. Like the tumor affecting wild adult walleyes, the transmitted tumors were restricted to the dermis and originated from the superficial surface of scales. They never invaded locally and never metastasized. The transmitted tumors differed from tumors of adult walleyes in their severity and the absence of osteoid. The multicentric origin of transmitted walleye dermal sarcoma suggests that the virus spreads systemically and that tumor cells are polyclonal. This successful transmission of the lesion, along with the presence of C-type virus particles budding from tumor cells in two of seven tumor-bearing fingerlings, supports a retroviral etiology.     

Experimental Transmission of Discrete Epidermal Hyperplasia in Walleyes

Abstract

Two related retroviruses, designated walleye epidermal hyperplasia virus type 1 (WEHV1) and type 2 (WEHV2), have been identified in discrete epidermal hyperplasia skin lesions from adult walleyes Stizostedion vitreum. A transmission experiment was conducted in an effort to provide evidence for a viral etiology and to develop a model for pathogenesis studies. Cell-free filtrates derived from discrete epidermal hyperplasia lesions and known to harbor WEHV1 and WEHV2 were injected into young-of-the-year (age-0) walleyes. Discrete epidermal hyperplasia developed in 97% of walleyes inoculated with lesion filtrates; whereas those injected with a cell-free filtrate of normal walleye skin did not develop lesions. The presence of WEHV1 or WEHV2 was detected by polymerase chain reaction (PCR) assay. Amplified DNA products from the PCR assays indicated the presence of viral sequences in 100% and 69% of the skin lesions for WEHV2 and WEHV1, respectively.     

Transmission of Walleye Dermal Sarcoma and Lymphocystis via Waterborne Exposure

Abstract

A study was conducted to determine if walleye dermal sarcoma could be experimentally transmitted by waterborne exposure of tumor-free walleyes Stizostedion vitreum to tumor-positive walleyes by cohabitation. Uninfected walleyes were placed in a common raceway with tumor-positive fish for either 5 or 15 d. Direct contact between the two groups of fish was prevented by two screen barriers. The exposed fish were then maintained in the laboratory for a total of 20 weeks. Walleye dermal sarcoma developed in 89% and 71% of the fish exposed for 5 and 15 d, respectively. There was no significant difference (P > 0.05) in incidence of tumors between the two groups of fish exposed for different lengths of time.     

Effects of Water Temperature on Experimental Transmission of Dermal Sarcoma in Fingerling Walleyes

Abstract

The effects of temperature on experimental transmission of dermal sarcoma, a spontaneous tumor of adult walleyes Stizostedion vitreum to fingerling walleyes was determined. Test temperatures were 10, 15, and 20°C. Three-month-old walleyes were inoculated intramuscularly with a cell-free filtrate from a dermal sarcoma collected from an adult walleye in the spring of the year. Tumors were first grossly visible in fish held at 15°C at 8 weeks postinoculation. At 12 weeks postinoculation, all fish were euthanized and examined for presence of tumors. Tumor transmission was most successful at 15°C, followed by that at 20°C; many fish maintained at these temperatures had grossly visible tumors. Although the majority offish held at 10°C also had tumors, tumors in these fish developed to a lesser degree than those observed in fish held at the higher temperatures.     

Susceptibility of Selected Inland Salmonids to Experimentally Induced Infections with Myxobolus cerebralis,the Causative Agent of Whirling Disease

Abstract

Laboratory exposures to the infectious stages (triactinomyxons) of Myxobolus cerebralis demonstrated a range of susceptibility to whirling disease among four species of inland salmonids. Replicate groups of each species were exposed to two concentrations of triactinomyxons, a low dose (100–200 per fish) and a high dose (1,000–2,000 per fish). Exposed fish were evaluated for clinical signs, for severity of microscopic lesions at 35 d, 2 and 5 months, and for spore concentrations in the head cartilage at 5 months. A standard strain of rainbow trout Oncorhynchus mykiss matched for age served as a susceptible species control. Rainbow trout, westslope cutthroat trout O. clarki lewisi, Yellowstone cutthroat trout O. clarki bouvieri, and bull trout Salvelinus confluentus were susceptible to M. cerebralis infections. Clinical signs, including radical swimming (“whirling”) and black tails, were observed at 7 weeks postexposure among rainbow and cutthroat trout challenged at 3 weeks of age. Clinical signs were rare among bull trout exposed at an age of 4 weeks and absent among rainbow and cutthroat trout exposed at 3 months posthatch. Most rainbow, cutthroat, and bull trout were found to be infected when examined at 5 months postexposure. The most severe microscopic lesions among infected fish at 5 months postexposure were found among rainbow trout. Cutthroat trout had less severe lesions, bull trout had mild infections, and no evidence of infection was found among Arctic grayling Thymallus arcticus. Mean spore concentrations among infected fish correlated with the severity of microscopic lesion scores. Rainbow trout had mean concentrations of spores in head cartilage reaching 10⁶, whereas more resistant species such as bull trout had 10⁴ spores; no spores were found among Arctic grayling at 5 months postexposure.     

Regression of Dermal Sarcoma in Adult Walleyes

Abstract

Dermal sarcoma is a benign skin tumor of walleyes Stizostedion vitreum, and a seasonal prevalence for this condition has been observed in feral fish. This study was conducted to determine if dermal sarcomas regress. Evidence of dermal sarcoma regression was documented on individually identified adult walleyes. Degree of regression was variable, ranging from none to complete. This report provides the first definitive evidence that dermal sarcoma does regress seasonally from spring to summer.     

Ether Sensitivity of the Walleye Dermal Sarcoma Virus

Abstract

Current evidence supports the classification of the virus causing dermal sarcoma on walleyes Stizostedion vitreum as a member of the family Retroviridae. One of the characteristics of this group of viruses is the presence of a lipid envelope. In this report we document studies conducted that demonstrate the presence of a lipid envelope on the walleye dermal sarcoma virus.     

Evaluation of 1-stage and 2-stage selection in yellow perch I: genetic and phenotypic parameters for body weight of F1 fish reared in ponds using microsatellite parentage assignment

Two selection methods, 1-stage selection (OSS) and 2-stage selection (TSS), for improving efficiency and profitability of selective breeding of yellow perch were evaluated, through examining the genetic and phenotypic parameters for BW of F(1) fish using microsatellite parentage assignment in this study. Approximately 94% of the sampled yellow perch progeny were assigned to single parental pairs using 8 microsatellite markers, which confirmed the applicability of the communal rearing technique in yellow perch breeding. Within OSS, the genetic correlation between 1-yr-BW and 2-yr-BW was high (0.98), indicating that the growth of yellow perch recorded at yr 1 could predict their growth for yr 2. Also mean family BW and family EBV for BW between yr 1 and 2 were found to be significantly correlated, suggesting yr 1 fast-growing yellow perch families continued to be the fast growing families in yr 2. Two-year random fish undergoing TSS were significantly heavier (P < 0.01) than those undergoing OSS. In addition, top males and females with TSS were heavier (P < 0.01) than those with OSS. Based on these results we concluded that the TSS was more desirable and effective for yellow perch breeding compared with OSS in terms of improving selection efficiency and reducing costs.     

Lesions of so-called flank biting and necrotic ear syndrome in pigs

Skin lesions were established on the flanks of pigs aged 10 to 12 weeks, in the areas of the ribs, the mid-upper leg, the shoulder and the tuber ischii. Skin lesions on the ear tips, known as porcine necrotic ear syndrome, were detected in weaners throughout the raising period. By the histological examination of 50 samples of skin lesions from the flank, two stages of epidermal and dermal changes were established; the milder stage had epidermal changes with marked acanthosis, rete ridges formed deep in the dermis and mild infiltrates of mononuclear cells in the layers around the capillaries in the dermis; the more severe stage had ulcers, under which there were infiltrates of polymorphonuclear cells. The same histological changes were observed in 23 samples of skin lesions taken from the tips of ears with necrotic ear syndrome. On healthy skin from the flank and ear tip, micrococci were the dominant organism, whereas on skin lesions from both the affected areas staphylococci were dominant. Since the histological lesions on the flanks were identical to those in necrotic ear syndrome, which has been associated with Staphylococcus hyicus infection, the pathogenesis of the lesions on the flanks is probably the same.     

P‐33 Poxvirus infection in two cats

A 3‐year‐old Burmese cat was presented with a history of nonresolving crusted and papular lesions of the face and prior treatment with prednisolone. Skin biopsies revealed typical pox lesions with hyperplasia and ulceration of the epidermis and eosinophilic cytoplasmic inclusion bodies in the epidermal cells. In the upper dermis there was prominent diffuse mast cell infiltration and mild neutrophilic and eosinophilic inflammation. Rare cytoplasmic inclusion bodies were also present in swollen endothelial cells of dermal venules, which showed no other degenerative changes. Histological diagnosis was confirmed by electron microscopic evidence of pox virus particles in inclusion bodies of epidermal cells. The lesions resolved within 6 weeks with systemic antibiotic therapy and supportive care. A 2‐year‐old domestic short‐haired cat was presented with multiple disseminated papular and ulcerative pox lesions with central eschar over the entire body. Histologically, large epidermal inclusion bodies (up to 6 μm in diameter) were present. Widespread haemorrhage and vascular wall necrosis was visible in the dermis and subcutis. Some subcutaneous vessels showed neutrophilic vasculitis. In addition to diffuse dermal neutrophilic and eosinophilic inflammation, a lymphohistiocytic panniculitis was also present. The cat died as a result of massive haemorrhage and lymphedema, despite supportive care. Funding: Self‐funded.     

P-35 Nonlethal junctional epidermolysis bullosa in a dog

A 3-year-old Burmese cat was presented with a history of nonresolving crusted and papular lesions of the face and prior treatment with prednisolone. Skin biopsies revealed typical pox lesions with hyperplasia and ulceration of the epidermis and eosinophilic cytoplasmic inclusion bodies in the epidermal cells. In the upper dermis there was prominent diffuse mast cell infiltration and mild neutrophilic and eosinophilic inflammation. Rare cytoplasmic inclusion bodies were also present in swollen endothelial cells of dermal venules, which showed no other degenerative changes. Histological diagnosis was confirmed by electron microscopic evidence of pox virus particles in inclusion bodies of epidermal cells. The lesions resolved within 6 weeks with systemic antibiotic therapy and supportive care. A 2-year-old domestic short-haired cat was presented with multiple disseminated papular and ulcerative pox lesions with central eschar over the entire body. Histologically, large epidermal inclusion bodies (up to 6 μm in diameter) were present. Widespread haemorrhage and vascular wall necrosis was visible in the dermis and subcutis. Some subcutaneous vessels showed neutrophilic vasculitis. In addition to diffuse dermal neutrophilic and eosinophilic inflammation, a lymphohistiocytic panniculitis was also present. The cat died as a result of massive haemorrhage and lymphedema, despite supportive care.
Funding: Self-funded.     

The relationship between Adirondack lake pH and levels of mercury in yellow perch

Levels of total mercury in yellow perch Perca flavescens from Adirondack lakes were studied in relation to characteristics of the lakes to determine why some lakes had fish with higher concentrations of mercury. Almost all mercury in fish is in the form of methylmercury, which can pose significant health hazards to humans who consume such fish. Fish mercury concentrations and water chemistry data were analyzed from eight Adirondack lakes. Four lakes (Halfmoon Lake, Sand Pond, Rock Pond, and Upper Sister Lake) had pH values of less than 5.0. Four other lakes (Lake Adirondack, Kings Flow, Harris Lake, and Lake Kushaqua) had pH values of more than 7.0. The acidic lakes also had high levels of aluminum and low acid-neutralizing capacity relative to the neutral lakes. Yellow perch (n = 100) from the acidic lakes had significantly higher levels of mercury than did those (n = 102) from the neutral lakes (P < 0.001), and the total mercury concentration increased with both length and weight of the fish. We conclude that the pH of the lake water is a major factor in determining the concentration of methylmercury in yellow perch.     

Seasonal Occurrence of Virally Induced Skin Tumors in Wild Fish

Abstract

Seasonal trends in the prevalence of virally induced skin tumors are reviewed for a variety of wild fish with emphasis on neoplasms in the walleye Stizostedion vitreum. The relationship of temperature to mechanisms of virally induced tumorigenesis and regression in fish is also summarized. Particular emphasis is placed on teleost physiological parameters such as the immune response and endocrinological levels. Other elements of a multifactorial hypothesis for seasonal tumor fluctuations in fish are also discussed.     

A Viral Disease in Larvae and Juveniles of the Japanese Flounder Paralichthys olivaceus

Abstract

From 1985 to 1987, outbreaks of a disease resulting in mass mortality occurred in larvae and juveniles of the Japanese flounder Paralichthys olivaceus cultured at prefectural and private hatcheries in Hiroshima Prefecture, Japan. The disease occurred in 10-30-d-old fish that were reared at about 18–20°C, and mortality usually reached 80–90% in a few weeks. The affected fish had opaque fins and a hyperplastic epidermis on the fins and skin. Electron microscopy revealed hexagonal virus particles in the nucleus (100–140 nm in diameter without an envelope) and cytoplasm (190–230 nm with an envelope) of the affected epidermal cells. Although isolation of the causative agent by the use of five fish-cell cultures was not successful, the disease was transmitted to healthy larval flounder by exposing them to a 0.45-μm filtrate of diseased fish homogenate. The agent's morphological features and its sensitivity to ether, to a pH of 3, and to a 30min exposure to 50°C indicate it is a herpesvirus.     

Effect of Indomethacin on the Development of Proliferative Gill Disease

Abstract

After parenteral treatment with the cyclooxygenase inhibitor indomethacin, channel catfish Ictalurus punctatus were exposed to mature spores of an Aurantiactinomyxon sp. demonstrated to be the etiological agent of proliferative gill disease (PGD). Fish that received indomethacin at a dose of 2.0 or 5.0 mg/kg body weight within 0.5 h before exposure to the myxozoan and again at 24 h postexposure had significantly (P < 0.05) less severe gill lesions 7 d after exposure than fish that received the drug vehicle alone. Fish that received 0.5 mg indomethacin/kg had moderately severe lesions. All fish were confirmed to be infected with the organism associated with PGD by microscopic examination of gills 4 or 7 d postexposure. These results suggest that products of the cyclooxygenase pathway (e.g., prostaglandins) participate in the pathophysiologic host response to PGD.     

Transmission of Edwardsiella ictaluri from Infected,Dead to Noninfected Channel Catfish

Abstract

Enteric septicemia of catfish (ESC) was transmitted horizontally from channel catfish Icialurus punctatus that had died from Edwardsiella ictaluri infection to contact channel catfish during 2 d of habitation in a tank. The contact channel catfish became positive for E. ictaluri antibody, became infected with this bacterium, and had signs of ESC and died within 12 d postexposure. Edwardsiella ictaluri was recovered from 24 of the 30 contact channel catfish that died from ESC, as well as from 9 of the 25 tested contact survivors. The cannibalizing of E. ictaluri-infected fish, or the shedding of E. ictaluri from dead fish, or both, were shown to be mechanisms of horizontal transmission of ESC among channel catfish.     

The effect of tricaine on use of the fluorescein test for detecting skin and corneal ulcers in fish

Fluorescein has been used for rapid and sensitive detection of fish skin and corneal ulceration. Effective use of the fluorescein test requires knowledge of conditions that might cause misleading interpretations or otherwise interfere with test reliability. Examination of fish health and the clinical workup often require tricaine as one of the most commonly used anesthetics. However, tricaine may interfere with correct interpretation of the fluorescein test and might also cause significant fish injury. The effects of tricaine exposure sequence on the fidelity of the fluorescein test was studied in Pacific halibut Hippoglossus stenolepis, walleye pollock Theragra chalcogramma, and northern rock soles Lepidopsetta polyxystra by examining the fluorescence of experimentally induced epidermal wounding. Tricaine can quench fluorescence that is emitted by fluorescein retained in skin ulcers, causing a false-negative reaction. Thus, for the fluorescein test to work properly, it is important to avoid the exposure of fluorescein-treated and rinsed ulcers to tricaine. The effects of exposure to buffered versus unbuffered tricaine on epidermal and corneal integrity were studied in Nile tilapia Oreochromis niloticus and channel catfish Ictalurus punctatus subjected to the fluorescein test and histological examination. Fluorescein could detect not only ulcers but also areas with only a partial loss of epithelium (i.e., erosion). The use of unbuffered tricaine to anesthetize these fish caused serious epidermal and corneal damage. If fish are euthanized with unbuffered tricaine for clinical workup, this severe epidermal or corneal damage could be misinterpreted as an antemortem lesion, leading to misdiagnosis. Even in water with alkalinity exceeding 50 mg/L as CaCO3, it would seem prudent to always buffer tricaine with sodium bicarbonate to prevent a pH change that might lead to iatrogenic effects from unbuffered tricaine. Thus, current general recommendations suggesting that tricaine does not need to be buffered in waters with alkalinity greater than 50 mg/L might need to be modified.     

Validation of a novel epicutaneous delivery system for patch testing of house dust mite‐hypersensitive dogs

Background – Patch tests with allergens are used for the evaluation of cellular hypersensitivity to food and environmental allergens in dogs and humans with atopic dermatitis. Viaskin is a novel allergen epicutaneous delivery system that enhances epidermal allergen capture by immune cells. Objectives – To compare the use of Viaskin and Finn chamber patch tests in dogs hypersensitive to mite allergens. Methods – Empty control or Dermatophagoides farinae house dust mite‐containing Viaskin or Finn chamber patches were applied to the thoracic skin of six mite‐hypersensitive Maltese‐beagle crossbred atopic dogs. Lesions were graded 49 and 72 h after patch test application, and skin biopsies were collected after 72 h. Overall microscopic inflammation, eosinophil and T‐lymphocyte infiltrations were scored. Results – Positive macroscopic patch test reactions developed at five of six Viaskin application sites and four of six Finn chamber application sites. Median microscopic epidermal and dermal inflammation, as well as eosinophil and CD3 T‐lymphocyte dermal scores were always higher in biopsies collected at Viaskin than at Finn chamber sites. Microscopic inflammation scores were significantly higher after mite allergen‐containing Viaskin compared with empty patches, but this was not the case for mite‐containing Finn chambers compared with control chambers. Scores obtained using Viaskin were not significantly different from those obtained using Finn chambers. Macroscopic and microscopic scores were significantly correlated. Conclusions and clinical importance – In mite‐allergic dogs, Viaskin epicutaneous delivery systems appear to induce stronger allergen‐specific inflammation than currently used Finn chamber patch tests. Consequently, Viaskin patches might offer a better alternative for screening cellular hypersensitivity to food and environmental allergens.     

Notoedric mange in two free-ranging North American racoons (Procyon lotor) in Japan

Mange was diagnosed in two North American racoons (Procyon lotor) at Kamakura City in Kanagawa Prefecture, Japan. The mites were identified morphologically as Notoedres cati. Mite infestation affected the skin over the extremities and tail, and was characterized by moderate alopecia and erythematous dermatosis. Histopathologically, the affected skin showed marked epidermal hyperplasia and mites located within the parakeratotic stratum corneum. A slight dermal inflammatory response consisting principally of mononuclear cells was observed. N. cati mites were demonstrated in their tunnels using scanning electron microscopy (SEM). This is the first report of notoedric mange in racoons.