The ongoing need for this work, as indicated by stakeholder input. The United States (U.S.) is the world's largest poultry producer, the second-largest exporter of poultry meat, and a major producer of eggs and egg products. The significant integration and growth over time places the poultry industry as one of the major contributors to U.S. animal agriculture and to the national economy overall. The combined value of production from broilers, eggs, turkeys, and the value of sales from chickens in 2022 was $77.0 billion, up 67% from $46.1 billion in 2022 (USPEA, 2023). Chicken eggs and meat are an important source of dietary protein and micronutrients for the U.S. population. Ten billion broiler chickens were hatched in 2022 up 1 percent from 2021 (USDA, NASS hatchery production summary, April 2023) and are now raised for meat consumption each year on over 25,000 U.S. farms (National Chicken Council data, 2022). American per capita consumption of all poultry continues to increase annually, estimated to be 113.9 pounds in 2022, with chicken being the top animal protein consumed nationally. Additionally, U.S. egg operations produced over 96 billion eggs per year, 69.2% are domestically consumed (retail and food service shell eggs, United Egg Producers data, 2020). Per capita egg consumption has increased significantly (~15%) over the last decade from 250 to 286. The U.S. has the largest broiler chicken industry and turkey industry globally, producing over 9.78 billion chickens and 210 million turkeys annually in 2023 (USPEA, 2023). Over 59 billion pounds live weight of broiler chickens is grown annually, with 16.6% of production being exported to other countries.            

Infectious diseases continue to be a major deterrent for poultry producers. Losses induced by infectious diseases of poultry have a major economic impact affecting local, national, and global economies. Many endemic infectious diseases in the U.S. continue to decrease the profitability of commercial poultry production. Losses from mortality and morbidity, at processing (via condemnations) and overall poor flock performance (increased feed conversion, medication costs, etc.) are the compounded effects of infectious diseases. Environmental factors and novel production systems may also contribute to the increased incidence, and severity of infectious diseases. Thus, preventative strategies are critical to control infectious diseases. Since infectious diseases are multifactorial in nature, improved understanding of the underlying factors that influence disease ecology in poultry production and the interrelatedness of disease agents is necessary knowledge for effective poultry disease prevention and control.  Studying emerging and reemerging infectious disease pathogens and pathogenesis improves detection, control, and prevention of infectious poultry diseases. The renewal of the NC-1180 project will further the understanding of the epidemiology and ecology of re-emerging and emerging diseases by exploring the complexity of polymicrobial relationships that occur between pathogens, the normal microbiota, and immunity during the disease and convalescent processes.  Of primary concern are infectious disease resurgences that periodically threaten the U.S. poultry industry such as avian influenza. However, control of other significant endemic poultry infectious diseases will be strongly addressed by the participants of this project. For example, the consumer driven demand for antibiotic-free animal protein sources, has led to the emergence and reemergence of persistent enteric and immunosuppressive poultry diseases that were previously of minor importance. Determining the economic impact of poultry infectious diseases is challenging. The “cost of infectious diseases” to the poultry industry varies widely from year to year depending on the endemic, emergent, and reemerging diseases present within a given year. The USDA reported that the cost of infectious diseases for broilers, eggs, turkeys, and sales of chickens for 2021 exceeded $3.6 billions of the production value of $46.1 billions. Taxpayers and consumers ultimately pay the cost of poultry infectious diseases. Recent cases of highly pathogenic avian influenza (HPAI) provide an excellent example. Consumers paid higher prices for poultry products during the HPAI outbreak of 2021-22 as evidenced by the increased price of eggs and turkey products during that period. As part of the disease control response by the USDA, the government compensates producers for those flocks that are depopulated due to avian influenza infections which further increases the cost to the taxpayer.

            Unfortunately, HPAI emerged again in late winter of 2021 and early spring of 2022 and is still sporadically appearing in U.S. flocks and other commercial operations around the world.  By comparison, as of this writing, in the 2021-23 HPAI outbreak an estimated 58.8 million birds were lost encompassing 325 commercial flocks and 511 backyard flocks and the full economic impacts are yet to be determined but are estimated to reach 3.5 billion dollars.  On May 17^th, 2023, National Turkey Federation Vice Chairman John Zimmerman testified about the industry’s priorities before the US House Agriculture Subcommittee on Livestock, Dairy and Poultry.  He related that “avian influenza vaccination is the number one priority”. He testified “An effective vaccine would be an important tool for eradication … But we must work together to identify potential vaccines and to modernize our trade agreements. No one should be afraid of sound scientific research and open negotiation with our trading partners.”

            The export market comprises a large portion of the U.S. poultry meat and egg production. Export markets are subject to immediate restrictions when infectious diseases such as HPAI or virulent Newcastle disease (VND) are diagnosed and reported in commercial flocks. HPAI and VND have continued to emerge/reemerge. The magnitude of losses caused by HPAI were well illustrated during the 2014-2015 outbreak. According to the USDA’s final report “Approximately 7.4 million turkeys and 43 million egg-layers/pullet chickens, as well as a limited number of mixed poultry flocks, were affected by HPAI and died from the disease or were depopulated as part of the USDA’s control response.

            Although HPAI remains one of the biggest threats to the U.S. poultry industry, other endemic, emerging, and reemerging poultry diseases compromise the profitability of poultry production in the U.S. The U.S. Animal Health Association (USAHA) Committee on Poultry and Other Avian Species (CPAS) 2022 report (Sato & Neil) separately ranked the most significant infectious disease issues of poultry commodities (broilers, breeders, pullets, layers, and turkeys). We consolidated the rankings of common infectious diseases among poultry commodities into one graph.   The highest-ranked infectious diseases are located at the bottom of the graph. Overall, this project will address one or various aspects (epidemiology, diagnosis, host interactions, and disease control) of eleven (indicated as red bars) of the twenty most significant current poultry diseases.

Bars in red indicate the diseases that will be addressed in the renewal project. Please see the Attachments section for this figure.

             Based on the USAHA report variants of infectious bronchitis virus (IBV), infectious laryngotracheitis virus (ILTV), lentogenic and velogenic Newcastle disease virus (NDV), Avibacterium paragallinarum (AP) the causative agent of Infectious coryza, avian mycoplasmas (Mycoplasma gallisepticum), Ornithobacterium rhinotracheale (ORT), Escherichia coli, and Pasteurella multocida are among the more impactful respiratory agents that have the potential to damage protective airway mucosa and either themselves, or secondary opportunistic pathogens, invade body tissues. Potentially these infections may lead to systemic spread (sepsis/septicemia) and consequently to significant economic losses due to poor performance (increased feed conversion and medication costs, decreased growth), bird mortality (death), or condemnation of carcasses at processing. Environmental factors and novel production systems may also promote the incidence of these pathogens or exacerbate clinical signs and lesions. Thus, preventative strategies including poultry management are critical to control respiratory diseases of poultry. As these diseases are multifactorial in nature, improved understanding of the underlying factors driving the ‘respiratory disease complex’ are necessary, including understanding the role of immunosuppression in disease development and understanding the polymicrobial relationships that occur between pathogens and the normal microbiota during the disease process.

             Among the immunosuppressive diseases of poultry, a well-recognized immunosuppressive agent is infectious bursal disease virus (IBDV) which can severely deplete immune cells responsible for naturally detecting and controlling infections. Birds with immunosuppressive diseases are unable to respond properly when other infectious agents are encountered and are more severely affected when secondary infections occur.  Another continuous battle of the poultry industry is to maintain flocks adequately protected through vaccination against the alpha-herpesvirus Marek’s disease virus (MDV) the cause of a common lymphoproliferative disease of chickens. Although MDV vaccines protect against tumor formation, virulent strains frequently induce immunosuppression altering the susceptibility of chickens to other diseases. Another debilitating viral disease that significantly affects poultry production is caused by avian reoviruses (ARV). Increased incidence of tenosynovitis/viral arthritis in broiler chickens due to the emergence of new genotypes and serotypes of ARVs are problematic. Thus, studying immune responses under immunosuppressive conditions in association with disease pathogenesis furthers our understanding on control of the pathogen and disease. In turn, we can tease apart complicated, multifactorial infectious disease expressions. It is imperative to engage in active surveillance and continued research of infectious poultry diseases using a holistic approach while developing strategies for enhancing biosecurity, vaccination, and control for these economically important diseases. This renewal of the NC-1180 project will take a more synergist and holistic approach exploring the “disease triad” of the interplay between host, environment, and disease agents.       

 b) The importance of the work. In our NC1180 2023 meeting in August we invited poultry experts from the layer, broiler, and turkey sectors to present and discuss those poultry health / disease issues that are of highest priority. After the stakeholders’ presentations the NC1180 group summarized the stakeholders input and determined how we could have the greatest impact. Six main aims were identified: Need for broadly protective vaccines; b. better understanding of the pathology and epidemiology of reovirus infections; c. the role of infectious diseases in early chick mortality; d. detection and reduction of pathogen in the chicken house environment; e. understanding the role of current emergent immunosuppressive diseases in multifactorial infections of poultry; f. improving the mass administration of poultry vaccines.  We ascertain that the renewal project will address these aims with the expectation of having significant impact. The NC1180 participants will continue to address diagnosis, control, and prevention of emerging and endemic infectious poultry diseases. Vaccine development and use of novel vaccine technologies will also be addressed. Complacency and compliance are often the downfall of programs that are essential for the control of infectious diseases. Participants of this project will actively continue to educate poultry producers and veterinarians about best practices for disease surveillance, biosecurity, and control of infectious diseases of poultry. Additionally, the NC-1180 group is committed to hold a “stakeholder listening sessions” during their annual meetings in order for the group to maintain its relevance and continue to advance knowledge and efforts to protect our nation's food supply and the economic well-being of poultry producers considering the newer challenges posed by emerging and reemerging poultry infectious diseases and producing poultry without use of antimicrobials. 

 c) The Technical Feasibility of This Project. We realize there are many technical challenges to achieve the goals and objectives of this project. Although the “disease triad”, often used to illustrate the relationships between host, environment, and disease agent, seems straight forward and clear-cut, often it is a complex entity that requires alternative and holistic approaches. The objectives of this project are feasible and realistic because the project participants have the experience, training, and expertise in a range of disciplines, and they will be interacting collaboratively to achieve mutual success. The current NC1180 group includes a diverse group of scientists with expertise in poultry medicine, virology, microbiology, vaccinology, immunology, genomics and bioinformatics, biosecurity, and extension. The scientist within this project lead research in at least 28 independent laboratories representing nine institutions across 10 U.S. states [AL (5), CA (3), DE (6), GA (5), IL (1), IA (5), MD (4), MN (1), NE (2)]. Seven USDA scientists (SEPRL) collaborate on the project. Conducting this work as a multistate effort allows for the greatest efficiency of resource use among these scientists.

 d) Advantages for doing the work as a multistate effort (The Essential Collaborative Nature of this Project). This project is focused on infectious diseases of poultry which encompasses numerous poultry pathogens in a diversity of host systems. The complexity of disease pathogenesis and control of infectious diseases requires multiple disciplines and approaches and thus lends itself to collaborative multistate research. The multistate effort achieves synergism by participants sharing and exchanging ideas, biological materials, facilities, research equipment, expertise, and coordinated support. No single station possesses all the expertise and facilities needed to address all the poultry infectious disease and management issues included in this project. The use of a team approach enables us to perform cross-disciplinary and multiple poultry industry (i.e., broiler, layer, turkey, etc.) research with translatable value. The current NC-1180 project has served as a venue for gathering, discussing, and providing critical information on respiratory disease status of poultry at the state and national level which has incentivized research projects and collaborations among members of the group, with industry, and state and federal personnel. Major impacts from the current project include new approaches to detect respiratory pathogens using next generation sequencing for the rapid identification and prediction of pathogenicity of bacterial and viral pathogens. Host resistance aspects to IBV and ILTV have been uncovered, knowledge on the adaptation process of waterfowl avian influenza to poultry, and effects of viral immunosuppression on AIV shedding. Novel vaccine candidates for IB, ILT, and NDV are among some of the contributions of the current NC-1180 project on respiratory diseases of poultry (2019 – 2023). In the new proposed effort, we will further expand the impact towards the understanding of enteric and immunosuppressive diseases and how these intensify the persistence of respiratory diseases. Note that the NC-1180 project objectives synergize with the NE-1834, Genetic Bases for Resistance and Immunity to Avian Diseases. The participation of some of the members in both projects allows for excellent coordination between the two multi-state projects, ensuring good communication and collaboration while avoiding duplicative efforts. We recognize that there are other multistate research projects, like the NC-1202, which emphasizes food safety and the control of enteric diseases of all livestock and poultry species. The NC-1180 focus will be to explore the interactions of enteric, respiratory, immunosuppressive, and other pathogens to promote flock health and well-being.e) Outcomes and Impacts of this Project. The overall impact of a successful outcome will be improved understanding of the ecology, pathobiology, epidemiology, diagnosis, and control of major poultry infectious diseases. These outcomes will not only benefit the poultry industry but also the food security of our country. Impact of this research will be derived from identification and characterization of disease agents, their reservoirs, factors involved in agent transmission to poultry, development and delivery of novel, fast and accurate molecular and protein-based diagnostics, determination of infection status, rapid pathogen and strain identification or characterization, evaluation and development of vaccines, and the design and implementation of eradication protocols for select agents. Findings from this project will assist poultry producers to remain competitive and profitable while promoting poultry health and well-being.

Scientists of the NC-1180 Project, Endemic and Emerging Infectious Diseases of Poultry in the United States