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Title: VIRUS-INDUCED NEOPLASTIC DISEASES OF TURKEYS: AN UPDATE

Author
item Fadly, Aly
item Witter, Richard
item CRESPO, R - UNIV OF CALIFORNIA FRESNO
item DAVIDSON, I - KIMRON VET INSTITUTE
item HAFEZ, H - BERLIN FREE UNIVERSITY

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/16/2004
Publication Date: 6/16/2004
Citation: Fadly, A.M., Witter, R.L., Crespo, R., Davidson, I., Hafez, H.M. 2004. Virus-induced neoplastic diseases of turkeys: an update [abstract]. 5th International Symposium on Turkey Diseases. p. 18.

Interpretive Summary:

Technical Abstract: Virus-induced neoplastic diseases of turkeys are caused primarily by retroviruses, namely reticuloendotheliosis (RE) virus (REV) and lymphoproliferative disease (LPD) virus (LPDV). However, Marek's disease (MD), a herpesvirus-induced T-cell lymphoma of chickens, has recently been diagnosed in commercial turkey flocks in Germany, France and Israel. These recent findings suggest that the host range of MD virus has apparently expanded to include turkeys. More studies are needed to understand: a) conditions that lead to MD outbreaks in commercial turkeys, and b) economic significance of such outbreaks. As the principal virus-induced neoplasm of turkeys, RE is expressed as chronic lymphomas (reticular cell tumor or T-cell lymphoma). Although REV is widespread, the clinical disease is infrequently diagnosed in commercial turkey flocks. However, economic losses from REV infection in affected turkey flocks can be significant due to tumor mortality and loss of production. The principal economic concerns of REV infection remain as: a) contaminants of live-virus vaccines of poultry, or b) a barrier to export of breeding stock to certain countries. To date, no vaccines are available for control of REV infection and no method has been routinely used by industry to control REV infection in either commercial turkey or chicken flocks. However, some turkey breeders have experimented with programs similar to that used in eradication of avian leukosis virus (ALV). Recent studies have shown that REV genome can be partially or completely inserted in large DNA avian viruses such as MDV and fowlpox virus. Clearly, further studies are needed to determine the role of such insertion in the epidemiology of REV as well as the pathogenicity of these large DNA viruses. LPD, a neoplastic disease of turkeys caused a retrovirus (LPDV) unrelated to ALV or REV, had been reported in the past in Europe and Israel. The incidence of LPD of turkeys has always been sporadic and the disease has not been reported during at least the last decade. The economic significance of this disease condition in commercial turkeys remains obscure.