GENETIC AND BIOLOGICAL DETERMINANTS OF AVIAN TUMOR VIRUS PATHOGENICITY, TRANSMISSION, AND EVOLUTION
Location: Avian Disease and Oncology Laboratory
Title: An overview of tumorous diseases of turkeys
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2012
Publication Date: December 19, 2012
Citation: Fadly, A.M. 2012. An overview of tumorous diseases of turkeys. In: Proceedings of the 9th International Symposium on Turkey Diseases, June 21-23, 2012, Berlin, Germany. p.178-182.
This overview is primarily aimed at addressing various aspects of virus-induced tumorous diseases of turkeys including review of current methods for diagnosis and control of these diseases of turkeys. Virus-induced tumorous diseases of turkeys are caused primarily by retroviruses, namely reticuloendotheliosis (RE) virus (REV) and lymphoproliferative disease (LPD) virus (LPDV). Although Marek’s disease (MD), a herpesvirus-induced T-cell lymphoma of chickens, has been diagnosed in commercial turkey flocks in several countries, the conditions that lead to, and the economic significance of such MD outbreaks are poorly understood.
The economic losses from REV infection in affected turkey flocks can be significant due to tumor mortality and loss of production. REV infection in turkeys is primarily expressed as chronic lymphomas (reticular cell tumor or T-cell lymphoma). 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. Partial or complete REV genome insertion in large DNA avian viruses such as MD and fowlpox viruses have been well documented, suggesting a role of such insertion in the epidemiology and transmission of REV infection in both chickens and turkeys. The incidence of LPD of turkeys has always been sporadic and the disease has not been reported in commercial turkeys during at least the last two decades. Most recently, however, LPDV infection and tumors were reported in wild turkeys in the Southeast United States (Brown et al., United States Animal Health Association Meeting, Buffalo, NY, 2011). This report by Brown et al. represents the first time ever that LPDV infection was recognized in the USA. At this time, the economic significance of LPDV infection in wild turkeys in the Southeastern United States and the possibility of transmission of the infection to commercial turkey flocks are unclear.