Pathology of Tumors in Fish Associated With Retroviruses

Abstract

Thirteen proliferative diseases in fish have been associated in the literature with 1 or more retroviruses. Typically, these occur as seasonal epizootics affecting farmed and wild fish, and most lesions resolve spontaneously. Spontaneous resolution and lifelong resistance to reinfection are 2 features of some piscine retrovirus-induced tumors that have stimulated research interest in this field. The purpose of this review is to present the reader with the epidemiological and morphological features of proliferative diseases in fish that have been associated with retroviruses by 1 or more of the following methods: detection of C-type retroviruslike particles or reverse transcriptase activity in tumor tissues; successful tumor transmission trials using well-characterized, tumor-derived, cell-free inocula; or molecular characterization of the virus from spontaneous and experimentally induced tumors. Two of the diseases included in this review, European smelt spawning papillomatosis and bicolor damselfish neurofibromatosis, at one time were attributed to a retroviral etiology, but both are now believed to involve additional viral agents based on more recent investigations. We include the latter 2 entities to update the reader about these developments. Keywords fishes, piscine, neoplasms, Retroviridae, tumor virus infections, oncogenic virusesMembers of several virus families have been implicated in the etiology of tumors in fish. The literature contains numerous publications in which members of virus families Herpesviridae, Papillomaviridae, and Retroviridae are associated with the development of tumors in fish. In this report, we review the epidemiological, gross, microscopic, and ultrastructural features of 13 piscine tumors reported in the literature for which there is evidence of a retroviral involvement. In some instances, the evidence supporting a retroviral association is compelling and includes viral sequencing and successful transmission trials using a well-characterized inoculum. In other instances, a retroviral association is based on detection of retrovirus-like particles or reverse transcriptase activity in tissues from proliferative lesions. These viruses have been the subject of several reviews. 4,48,49 For this review, we have accessed archival materials primarily from the archived Registry of Tumors in Lower Animals as well as cases from the Aquatic Animal Health Program at the College of Veterinary Medicine, Cornell University.Before evaluating a lesion, any case of a fish tumor must be considered in light of the fish as an ectotherm. Much of the biology of fish is affected by water temperature and seasonality of various physiological processes. It is well known that the immune response in fish is modified by changes in water temperature and other physiological stressors, such as spawning activity. 39 A review of the case records of most fish disease diagnostic laboratories will show the largest number of neoplastic cases to occur in the spring, a time of changing water temperature and a tim...

Risk factors for development of internal neoplasms in koi carp Cyprinus carpio koi

“…Neoplasia is defined as uncontrolled proliferation and dispersal of autologous cells throughout the host body, resulting from accumulated DNA mutations (Martineau & Ferguson 2006). Some tumours in fish have been attri buted to genetic factors (Meierjohann & Schartl 2006, Nairn et al 1996; others were associated with a virus (Hanson et al 2011, Coffee et al 2013 or with environmental contamination (Fabacher & Baumann 1985, Baumann et al 1990, Harshbarger & Clark 1990. However, the presence of tumours in koi populations has not yet been extensively studied.…”

Transmission of a common intestinal neoplasm in zebrafish by cohabitation

“…Numerous neoplastic diseases of fishes have been shown to be caused by transmissible agents and are frequently associated with viruses (Anders & Yoshimizu, 1994; Coffee, Casey, & Bowser, 2013; Getchell, Casey, & Bowser, 1998; Schmale, 1995; Schmale, Gibbs, & Campbell, 2002). The origins of these neoplasms are usually skin epithelium, lymphoid or soft tissue (e.g., sarcomas), but to date no gastrointestinal cancers in fishes have been linked to viruses (Bowser & Casey, 1993; Getchell et al, 1998).…”

Dermal fibroma in a tawny nurse shark, Nebrius ferrugineus (Lesson, 1831)

“…Pollution may enhance carcinogenesis without directly causing tumours (Brown et al, ). Retroviruses were found to be associated with fibromas in many fish species (Coffee, Casey, & Bowser, ). No attempts were made in the present study for virus isolation.…”