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...

ABSTRACT:There are nine serotypes of avian paramyxovirus (APMV), including APMV-1, or Newcastle disease virus. Although free-flying ducks and geese have been extensively monitored for APMV, limited information is available for species in the order Charadriiformes. From 2000 to 2005 we tested cloacal swabs from 9,128 shorebirds and gulls (33 species, five families) captured in 10 states within the USA and in three countries in the Caribbean and South America. Avian paramyxoviruses were isolated from 60 (0.7%) samples by inoculation of embryonating chicken eggs; isolates only included APMV-1 and APMV-2. Two isolates (APMV-2) were made from gulls and 58 isolates (APMV-1 [41 isolates] and APMV-2 [17 isolates]) were made from shorebirds. All of the positive shorebirds were sampled at Delaware Bay (Delaware and New Jersey) and 45 (78%) of these isolates came from Ruddy Turnstones (Arenaria interpres). The APMV-1 infection rate was higher among Ruddy Turnstones compared with other shorebird species and varied by year. Avian paramyxovirus-2 was isolated from two of 394 (0.5%) Ruddy Turnstones at Delaware Bay in 2001 and from 13 of 735 (1.8%) Ruddy Turnstones during 2002. For both APMV-1 and APMV-2, infection rates were higher among Ruddy Turnstones sampled on the south shore of Delaware Bay compared to north shore populations. This spatial variation may be related to local movements of Ruddy Turnstones within this ecosystem. The higher prevalence of APMV in Ruddy Turnstones mirrors results observed for avian influenza viruses in shorebirds and may suggest similar modes of transmission.