Location: Exotic & Emerging Avian Viral Diseases Research
Project Number: 6040-32000-066-014-I
Project Type: Interagency Reimbursable Agreement
Start Date: Jul 1, 2015
End Date: Jun 30, 2020
Objective:
A highly pathogenic avian influenza virus has caused widespread oubtreaks in the United States resulting in major losses to the poultry industry. The virus causing the outbreak is closely related to viruses observed in Asia in 2014, and the virus appeared to be introduced into North America through wild birds. The goal of the research is to characterize the outbreak viruses originating from poultry and wild birds in relevant animal model species. Diagnostics tests will be developed or evaluated to make sure they are detecting outbreaks in wild birds or poultry. Control measures will be evaluated including vaccines. Available vaccines will be evaluated and tested against representative challenge strains to provide the data needed to determine if vaccines are an effective control tool. Finally, continued efforts with APHIS to monitor the virus as it evolves in the field is necessary to answer questions about epidemiology, and determine if vaccines or diagnostic tests need to be updated for effective control of the field virus.
Approach:
SEPRL will perform or coordinate research related to the H5Nx HPAIV that are currently found in the U.S. These studies will include evaluating the vaccine response to different vaccines that are likely to be commercially available for use in the United States. Currently three vaccines, the reverse genetics-H5N1 killed vaccine, the herpes virus of turkeys viral vectored avian influenza vaccine, and the alphavirus avian influenza will be compared in both chickens and turkeys. The vaccines studies will look at vaccination protocols that are likely to be practical for field application and will look at vaccination at different ages, duration of immunity, the additional benefit to booster vaccination with a single product or a combination of products. Most studies will include challenge with a virulent field strain to assess protection from clinical disease and determine the amount of viral shedding. Other vaccines may be evaluated if it is likely that they will become commercially available in the United States. Additional studies will be conducted in other poultry species, including quail, pekin ducks, other minor poultry species, or captive species to provide data on seroconversion and safety of the vaccine.
Additional studies will be conducted to look at the serologic DIVA monitoring potential for each of the vaccines. Vaccinated birds if infected after challenge are expected to seroconvert to unique proteins that can allow differentiation of vaccinated and vaccinated and infected animals. Being able to assure trading partners that exported poultry has not been exposed to avian influenza is important to maintain trade. Unfortunately little field data is currently available, and efforts to generate models of DIVA seroconversion parameters and surveillance requirements to assure a high level of confidence of freedom from infection will be performed. The serologic tests will use both commercially available tests as well as experimental ELISA tests that will be developed for the project to allow for efficient serologic testing.
Additional studies will be conducted to look at the virus evolution of the virus in both poultry and wild birds. In close coordination with APHIS, network sequence analysis will be used to see if the virus in poultry is changing over time, and whether it is likely introduced through wild birds to poultry or poultry to poultry spread. This type of information is critical to provide recommendations for biosecurity improvements. This data will also provide information on what are the important strains circulating in the field. It is expected that antigenic drift will occur in the field viruses, and alternative reverse genetics vaccines will need to be prepared for likely antigenic variants. Because of the considerable lag to produce and deselect reverse genetics produced vaccines, representative strains will be made on a periodic basis to provide the most flexibility as possible. The sequence data will also provide the information needed to assure molecular diagnostic tests are remaining effective in the rapid and sensitive diagnostics for field outbreaks.
