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 2013 substantial progress was made for all milestones and progress was made on all objectives of the project. The outbreak of H7N3 highly pathogenic avian influenza in Mexico was focus of work during FY 2013. Numerous aspects of the virus from Mexico were characterized including a vaccine study was completed to evaluate how well the official vaccine strain being used in Mexico worked with this virus. It was shown that proper vaccination should provide protection against disease. In addition numerous other influenza strains were tested to see if they would work as vaccines and several US origin strains were identified that could protect poultry against disease if exposed to the virus from Mexico. It was also confirmed that the current diagnostic tests being used in US veterinary diagnostic labs are adequate to detect the virus from Mexico. During FY 2013 a novel influenza virus emerged in China (called H7N9). The source of the H7N9 virus for people is unknown, however since unusual influenza viruses often come from birds studies were conducted to determine if this new strain could infect chickens, turkeys, ducks and other birds. Although the ability of the virus to infect birds varied by species, the H7N9 virus did not make any birds sick. Although additional work needs to be completed, this indicates that some birds may serve as carriers of the virus.
1. Detecting avian influenza viruses in wild birds. A wild bird surveillance study was conducted in the Black Sea region in Ukraine to identify avian influenza viruses. A total of 3634 samples were collected from 66 different species of birds. Sixty seven viruses were isolated covering many low pathogenicity avian influenza (LPAI) virus subtypes. Phylogenetic analysis of the HA and NA genes revealed possible ecological connections between the Black Sea region and Europe. The LPAI viruses were isolated mostly from mallard ducks, but also from shellducks, shovelers, teals, and white-fronted geese. This information furthers our understanding of the ecology of avian influenza viruses in wild bird species.
2. An evaluation of sample collection methods for avian influenza virus. There is no uniform procedure for collecting optimal specimens from poultry for avian influenza detection and proper specimens are crucial achieving the optimal sensitivity and specificity of testing. ARS scientists in Athens, GA evaluated numerous elements of the sample collection procedure for avian influenza virus with chickens including: swab construction type, transport media, transport of dry versus wet, the effect of removing the swabs in the field versus the lab, and the number of swabs which could be placed in a single vial to be test together. Some of the alternative procedures and materials were found to improve sensitivity over current methods. The optimal methods have been adopted by numerous labs, poultry companies and APHIS.
3. Susceptibility of avian species to North American H13 low pathogenic avian influenza viruses. Gulls are widely recognized reservoirs for low pathogenic avian influenza (LPAI) viruses; however, the subtypes maintained in these populations and/or the transmission mechanisms involved are poorly understood. We conducted a series of experiments with multiple North American strains of H13 LPAI virus in ring-billed gulls, mallard, chickens, and turkeys and showed that the susceptibility to H13 LPAI viruses varied between species and viral strain. The experimental results are consistent with existing surveillance data on H13 LPAI viruses in birds, and indicate that influenza viruses of the H13 subtype are strongly host-adapted to gulls, but rare spill-over into aberrant hosts (i.e., turkeys and ducks) can occur.
4. Evaluation of Chinese H7N9 avian influenza virus in different poultry species to determine risk of transmission to poultry and to humans. Avian influenza virus can cause important disease problems in poultry and on rare occassions can jump to humans causing clinical disease. In early 2013 a new avian influenza virus, H7N9, was identified as causing human infections and based on sequence information the virus was suspected to have come from a poultry source. In laboratory experiments, chickens, quail, muscovy ducks, Pekin ducks, Embed geese, and pigeons were challenged with the H7N9 virus. Birds from each group challenged became infected although none became ill, but quail and chickens shed large amounts of virus. This study provided strong data that chickens and quail likely played a critical role of virus spread from poultry to humans and supported the control program in poultry to eliminate the human health risk.Swayne, D.E. 2012. Impact of vaccines and vaccination on global control of avian influenza. Avian Diseases. 56(4): 818-828.