Oral Presentation International Veterinary Immunology Symposium 2016

The Role of Vaccines in the Evolution of Avian Herpesviruses – The Chicken and the Egg (#15)

Joanne Devlin 1
  1. University of Melbourne, Parkville, VIC, Australia

The avian alphaherpesviruses Marek’s disease virus (MDV) and infectious laryngotracheitis virus (ILTV) are economically significant viral pathogens of commercial poultry worldwide. Live vaccines have been used for decades to help prevent clinical signs of disease, but these vaccines do not prevent infection. Thus, wild-type viruses continue to circulate and evolve in vaccinated flocks. We have studied the evolution of ILTV in Australian poultry flocks over the last ten years using a combined approach of epidemiological studies, full genome sequencing and experimental infection studies. The results suggest that vaccine use has influenced the evolution of ILTV, particularly through the process of recombination. There is also evidence of evolution towards increased virulence and enhanced horizontal transmission dynamics in the most recently isolated, dominant field viruses. This is consistent with historical and recent studies of MDV where increasing virulence has been observed worldwide since MDV vaccines were first introduced over 40 years ago. Collectively, this highlights the importance of implementing vaccination programs to maximize vaccine safety and efficacy and also the importance of continued efforts to develop improved vaccines to control these diseases. ‘New generation’ ILTV vaccines, such as vectored vaccine and deletion-mutant vaccines are under development, or have recently been made available for commercial use. These are important contributions to disease control, but these vaccines also have limitations. It is essential to the ongoing economic success of the poultry industries worldwide that research into the development of vaccines that can prevent viral infection and shedding in vaccinated birds remains a high priority.