Experimental Transmission of a Dermal Sarcoma in Fingerling Walleyes (Stizostedion vitreum vitreum)

Abstract

Abstract. 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.Key words: Fish; neoplasm; retrovirus; transmission.Walleye dermal sarcoma is a benign skin tumor of adult fish diagnosed in adult walleyes from a number offish populations throughout North Amefica.g-ll The tumor has been most often observed during the spring removed from some of the fish at the hatchery and stored at -90 C until used. Other tumor-bearing walleyes were transported to Cornell University, where they were maintained in temperature-controlled holding Units (Frigid Units, Inc., Prevalence of the lesion is seasonal; it is common size (75 mm). Fingerling walleyes were obtained for this study in the spring and fall, but rare in the summer.' Walleye from the NYSDEC South Otselic Fish Hatchery on 22 June dermal sarcoma is also age-related; it is not observed 1988. Upon arrival in our laboratory, the fish were placed in sexually immature fingerlings. I in temperature-controlled holding units where they were kept In order to demonstrate the viral etiology for this without treatment during an acclimation period of 6 weeks. neoplasm and to provide a model for studying the During the entire holding period, the fish were provided a seasonal prevalence of dermal sarcoma, transmission ration of swim-up fathead minnow (Pimephales P o m e h )

Further evidence for a viral etiology in plasmacytoid leukemia of Chinook salmon Oncorhynchus tshawytscha

“…Our experiments also indicate that 1979, Gross 1983), dermal sarcoma of walleye Renibacterium salmoninarum and Enterocytozoon salStizostedion vitreum (Martineau et al 1990), and neumonis are not the cause of the disease. This concurs rofibromatosis of damsel fish Pomacentrus partitus Retroviruses have been associated with these lesions and other neoplasms of fishes (Papas et al 1976, Duncan 1978, Yamamoto et al 1985, Martineau et al 1990, Anders et al 1991. Retroviruses, including those that cause leukemias, are well recognized causes of immunosuppression.…”

EZR1: A Novel Family of Highly Expressed Retroelements Induced by TCDD and Regulated by a NF-κB-Like Factor in Embryos of Zebrafish (Danio rerio)

“…3) shows that EZR1 clusters with ERV4-DR1 (from RepBase), and appears to be related to the walleye (Stizostedion vitreum) dermal sarcoma virus described by Martineau et al [25][26][27][28] EZR1 integrase is less similar to the zebrafish endogenous retrovirus (ZFERV, ZFERV-2-I_DR) integrase described by Shen and Steiner 29,30 (23% amino acid identity), but…”

Comparative Pathogenesis of Epsilonretroviruses

“…A number of observations support this view of pathogenesis, including (i) the presence of abundant retrovirus type C particles in regressing tumors but not in developing tumors (14), (ii) observations that the gene expression patterns of the walleye retroviruses change both quantitatively and qualitatively during the course of the disease, with low levels of spliced RNA transcripts produced in developing tumors and high levels of spliced and unspliced viral transcripts produced in regressing tumors (42,61), and (iii) the experimental transmission of disease to walleye and sauger (a closely related species that interbreeds with walleye [Stizostedion canadense]) fingerlings by using cell extracts from regressing tumors but not from developing tumors (8,10,12,14,19,32,48). WDS has been transmitted to walleye fingerlings by using cell-free tumor filtrates as inocula and by waterborne exposure (8,(12)(13)(14)48). Generally, experimental transmission studies done with walleye fingerlings have produced WDS in 10 to 14 weeks that are typical of those seen in the fall on feral fish.…”