Mycotoxins Aflatoxin

Hepatic carcinomas in rainbow trout grown in hatcheries have been linked to feed contaminated with aflatoxin. However, the current interest in aflatoxin is related to experimental carcinogenesis. Hendricks (1994) reviewed the carcinogenicity of aflatoxin in fish and other nonmammalian species. Epizootics of hepatic carcinomas were discovered after dry feeds for trout came into wide use during the 1950s (Hueper and Payne, 1961 Rucker et al., 1961 Wood and Larson, 1961 Scarpelli et al., 1963),...

Anitroso Compounds

Glans Penis Juvenile

A-nitroso compounds are produced by reactions of amines with nitrites. These reactions occur in foods, cosmetics, tobacco products, cutting oils and in rubber manufacture (Tricker and Preussmann, 1991 Lijinsky, 1992). Several A-nitroso compounds have been shown to form spontaneously in sewage and lake water containing simultaneously high levels of nitrates or nitrites and dimethyl- or trimethylamines (Ayanaba and Alexander, 1974). It has also been reported that mutagenic A-nitroso compounds can...

Lipomas

Idiopathic lipomas occur sporadically and at low prevalence, and there is no indication of the cause of these benign neoplasms in wild or aquaculture fish. Lipomas have been reported in diverse species including dab (Bruno et al., 1991), European eel (Easa et al., 1989a) and striped mullet (Mugil cephalus) (Easa et al., 1989b). Channel catfish with lipomas were found in two commercial fish ponds and from a research pond none of these sites had any known carcinogenic contaminants (McCoy et al.,...

Herpesviridae Neoplasms

Herpes Virus Salmon

Three herpesviruses of salmonids have been reported to be oncogenic. Oncorhynchus masou virus (OMV) causes cutaneous carcinoma (Fig. 3.7) in coho salmon, chum salmon (Oncorhynchus keta), cherry salmon (Oncorhynchus masou) and rainbow trout (Kimura et al., 1981 Yoshimizu et al., 1987, 1988). This virus was originally isolated from apparently healthy cherry salmon, (Kimura et al., 1981). Yamame tumour virus (YTV) was first isolated from a neoplasm on the jaw of a cherry salmon (Sano et al.,...

Retroviridae Neoplasms

Retroviruses probably cause most infectious neoplasms of fish. These neoplasms are diverse and include lymphosarcoma or leukaemia, dermal sarcoma, fibroma, leiomyosarcoma, papilloma and neural neoplasms. Viruses causing these diseases are difficult to isolate in cell culture, but transmission of the disease by cell-free inoculum and presence of reverse transcriptase activity provide evidence that retroviruses are the aetiological agents causing certain neoplasms of fish. Virus-like particles,...

Thyroid Hyperplasia

Although thyroid neoplasms have been commonly reported in fish, most of these thyroid masses were probably goitres rather than neoplasms Harshbarger, 1984 Hoover, 1984b Leatherland, 1994 . Thyroid hyperplasia occurs most often in captive fish or in wild fish from certain geographical areas such as the Great Lakes. Prevalence of these lesions can be high, up to 93.5 in Lake Erie coho salmon Oncorhynchus kisutch , and the lesions can occur seasonally Leatherland and Sonstegard, 1980 . Causes of...