1a. Objectives (from AD-416):
1. Characterize variant and emerging avian influenza viruses in live poultry markets and commercial production systems. 2. Identify genetic and biological determinants of virulence, tissue tropism and host range of avian influenza virus. 3. Identify genetic and biological determinants of avian influenza virus susceptibility and resistance in avian species. 4. Improve existing diagnostic tests and testing strategies for avian influenza virus surveillance, detection, and recovery from disease outbreaks. 5. Develop new vaccine platforms designed to control and prevent avian influenza virus outbreaks.
1b. Approach (from AD-416):
These objectives include a combination of basic and applied research to give us the knowledge and tools to effectively control avian influenza virus (AIV). The first objective focuses on characterizing new and emerging strains of AIV, initially by genome sequencing and analysis, then by pathogenesis and transmission studies, and finally by antigenic characterization. The second objective will elucidate specific viral factors involved in pathogenesis and virulence at a molecular level including utilizaiton of variant isolates initially characterized under objective 1. The third objective will investigate the viral factors involved in transmission and host adaptation of AIV among avian species with reverse genetics and pathogensis studies. Under objective 4 diagnostic tests will be improved by characterizing novel isolates to assure specificity and by adapting novel technologies to improve sentivity and specificity. New vaccines will be developed and evaluated through a variety of approaches including antigenic and molecular characterization for objective 5.
3. Progress Report:
During FY 2012 substantial progress was made for all milestones and progress was made on all objectives of the project. The H5N1 “bird flu” was first seen in Egypt in 2006, and Egypt remains one of a handful of countries where the H5N1 bird flu continues to infect poultry. Since influenza can mutate rapidly it is crucial to maintain current genetic data on the virus, which provides information on virulence, whether diagnostic test will detect the virus and relationship with current vaccines (the more closely related it is to vaccines the better the vaccines work). Through a collaboration with Egypt SEPRL has obtain isolates through 2010 and has completed gathering genetic information and analyzing this information. It appears that the virus has now mutated into several groups which will make control more difficult because vaccine is less effective against the mutant groups. Monitoring of wild bird specimens for avian influenza virus (AIV) to understand influenza ecology has been an ongoing effort since 1998. Testing samples from wild birds for AIV by polymerase chain reaction (PCR) which detect the genetic material of the virus. If that test is positive attempts are made to detect live virus in the specimen, then analyze its genetics. In this last group of sample no live viruses were detected. This provides data that the types of birds tested probably do not harbor AIV. One of the most widely used diagnostic tests for AIV detects the genetic material of the virus, but the sensitivity can be affected by extraneous material in the sample or virus levels may be too low. One method to improve sensitivity is to incubate the sample in culture for a short time to increase the amount of virus. This is faster and cheaper than culture alone. Nine isolates of diverse origins were tested and it demonstrated that incubating sample material in culture for 24 hours could improve sensitivity by 10 and up to 100 times testing sample material directly. Substantial progress was also made in determining the genes involved in virulence for H5N1 highly pathogenic AIV infection in ducks and the effect of duck age and species on clinical disease. Vaccine work with ducks, chickens and turkeys continues including evaluating commercially available vaccines for efficacy against newly emerging strains of AIV and exploring how maternally derived immunity impacts vaccine efficacy. The Southeast Poultry Research Laboratory continues to collaborate with different Internation Organizations. This includes a Collaborating Center status with the World Organization for Animal Health (O.I.E.) on Avian Influenza and Newcastle Disease virus with the organization. In addition they were designated a Food and Agriculture Organization (FAO) Reference Center on Avian Influenza and Newcastle disease virus. We contribute research information and expertise for the control of these diseases around the world.
1. Reduction of high pathogenicity avian influenza virus in eggs from chickens once or twice vaccinated with an oil-emulsified inactivated H5 avian influenza vaccine. The presence of avian influenza virus in chickens eggs in areas where the virus is enzootic is a major concern because movement of infected eggs could spread the virus. It was shown that vaccination, even a single shot, could substantially reduce the levels of virus in the egg. This shows that vaccination of chickens at a high risk of infection with avian influenza virus could help prevent spread of the virus through eggs, which are often moved from the farm where they were laid.
2. Different species of ducks respond differently to vaccination against H5N1 highly pathogenic avian influenza. Domestic ducks are one of the most important reservoirs of the H5N1 highly pathogenic avian influenza virus because they are at high risk of exposure due to how they are reared and they can be infected without showing disease. Therefore vaccination is a key intervention to prevent infection of ducks, however there is not much known about how ducks respond to vaccination for avian influenza. This work showed that some of the most common domestic duck species (Muscovy and Pekin) do not responsd the same way to vaccines. With this information on how each species responds the most effective vaccine programs can be implemented for each species.
3. Avian influenza viruses infect egg laying chickens by different routes. Until recently it was thought that avian influenza virus was mainly transmitted among poultry by inhalation of infectious particles, however earlier work by our groups demonstrated that turkeys could be infected with the 2009 pandemic H1N1 [A(H1N1)pdm09] by artificial insemination. Work with low pathogenicity avian influenza virus in chickens demonstrated that they too could be infected by the reproductive route. This has implications for infection through artificial insemination and shows that the virus can replicate in the reproductive tract which may mean the the virus can be found in or on eggs.
Swayne, D.E., Pavade, G., Hamilton, K., Vallat, B., Miyagishima, K. 2011. Assessment of national strategies for control of high pathogenicity avian influenza and low pathogenicity notifiable avian influenza in poultry, with emphasis on vaccines and vaccination. OIE Scientific and Technical Review. 30(3):839-870.