Insights on epidemiology and control of immunosuppressive and neoplastic viral diseases of poultry

This doctoral thesis explores the molecular epidemiology and control of immunosuppressive and neoplastic diseseas of poultry, specifically Turkey Hemorrhagic Enteritis, Marek Disease, and Chicken Infectious Anemia. After an initial literature review, the thesis delves into studies centered on the control and the genetic characteristics of virus across different countries. The goal is to develop new molecular tools and broaden the epidemiological data reported in the literature. A molecular biology method targeting the ORF1 gene of turkey hemorrhagic enteritis virus (THEV), was developed to differentiate between vaccine-like and field strains. Three non-synonymous mutations – ntA1274G, ntA1420C and ntG1485A – were detected in field strains but not in the vaccine. This diagnostic tool was applied, with clinical and pathological approaches, in longitudinal field studies, demonstrating the efficacy and safety of a live attenuated vaccine against THEV. Molecular biology techniques targeting the full-length meq gene were used to characterize Marek Diseases Virus strains circulating in Israel. Analysis of the number of PPPPs within the proline-rich repeats showed that the virulence of the strains has increased over time, as evidenced by a decrease in the PPPPs number. The results support the validity of employing the meq gene molecular marker for the assessment of virulence in field GaVH-2 isolates. A final study on complete genome of chicken infectious anemia virus (CIAV) was included in the thesis, in order to investigate the epidemiological situation and the molecular characteristics of the CIAV strains circulating in Tunisia. The obtained strains exhibit a high degree of similarity, suggesting the circulation of a single CIAV strain, previously detected in Tunisia. The findings of this thesis offer valuable insights into the molecular epidemiology of immunosuppressive and neoplastic viral diseases, contributing to improved vaccination strategies and aiming to reduce the impact of these viruses on global poultry health and productivity.