The U.S. Department of Agriculture's Animal & Plant Health Inspection Service (APHIS) is currently monitoring two highly-pathogenic avian influenza (HPAI) virus strains in wild and domestic bird populations in the U.S.'s Pacific and Mississippi flyways.
Both strains of the virus have been found in other parts of the world and are capable of causing rapid, widespread mortality in commercial birds. H5N2 caused significant economic loss, mortality and depopulation of commercial poultry in British Columbia, Canada, throughout late 2014. H5N8 has been found in Asia and Europe over the past year and has resulted in the euthanasia of over 1 million birds to date1. In the U.S., as of March 13, there have been confirmed infections in Washington, Oregon, California, Idaho, Minnesota, Missouri and Arkansas in both non-commercial and commercial poultry flocks. While milder forms of the disease have occurred in the U.S. previously, the virus is not commonly found in commercial poultry.
The wild bird populations carrying the highly-pathogenic H5N2 and H5N8 are not as susceptible to these diseases and are the likely causes of spreading to commercial flocks. As such the virus could become more common in wild bird populations, which would increase risks to commercial flocks during seasons of wild water fowl migration. There has been no spread of HPAI from a commercial flock to any other commercial flock in the U.S. because of our control measures when a HPAI incident is detected.
Control and Response to HPAI in the U.S.
The network of state and federal agencies, working in conjunction with the poultry industry, has already executed procedures to quarantine any affected flock and reduce the impact of these instances. None of birds from the affected flocks are viable for sale and have not entered the food chain. In addition, the Centers for Disease Control & Prevention (CDC) and APHIS have confirmed there is no immediate public health concern with either of these avian influenza viruses.
USDA-APHIS conducts commercial surveillance and monitoring program through the National Poultry Improvement Program (NPIP). All USDA inspected facilities and breeders that export are members of NPIP. State veterinary programs conduct the routine surveillance for AI in domestic poultry. The NPIP program has a federally regulated testing and accreditation for freedom from certain diseases. Among these are Avian Influenza and Newcastle disease, among others, meaning all commercial flocks can be accredited “AI-Clean” through this program.
According to APHIS emergency management procedures, HPAI flocks are quarantined, and a buffer zone is established. Infected flocks are then depopulated with carbon dioxide or foam and composted or incinerated. Any other commercials flocks that test positive within the zone would also be depopulated. Fortunately, in the U.S., there is an indemnity program and pays farmers when poultry needs to be depopulated. Because of this depopulation, HPAI has not spread in commercial poultry. Instead, it is point infections along the migratory path of water fowl.
As a reminder, though, proper handling and cooking of poultry to an internal temperature of 165 °F kills all bacteria and viruses.
Biosecurity is Essential
In the case of each outbreak, the industry has worked cooperatively with federal, state and local authorities to contain and eradicate the disease through depopulation according to recommendations of the World Organization for Animal Health (OIE). The persistent reoccurrence of the virus, however, is concerning and necessitates that the poultry industry adopts a heightened awareness of biosecurity throughout production complexes.
Dr. Patricia Fox of USDA-APHIS Veterinary Services recently stated there is only one way to combat avian influenza in commercial flocks: “Biosecurity, biosecurity, biosecurity!” Methods must include physical precautions, as well as an understanding of the common means of transmission.
Migratory Birds and Open Water
The specifics of how avian influenza spreads from bird to bird are not well understood, but it is widely recognized that waterfowl, such as ducks and geese, appear to carry avian influenza with less negative impact to their health. They are therefore able to shed the virus in their environment for an extended period of time. The virus is able to span large distances due to the migratory nature of the host species. According to Dennis Alexander at the United Kingdom Animal and Plant Health Agency: “There is a much higher prevalence of infection of poultry on migratory waterfowl routes although…this may occur more frequently at some stages of the migratory route than others, e.g. Minnesota…compared to other states on the Mississippi flyway”2,3. Consequently, the majority of documented outbreaks in non-commercial flocks have pointed to contact with waterfowl at a congregating site, such as a pond or lake on the property. It should be noted that direct contact with waterfowl at a water site is not necessary for poultry to come in contact with virus, especially in colder temperatures. It has been estimated that the influenza virus can still cause infection in lake water for up to 4 days at 71°F and more than 30 days at 32°F4. It is, therefore, strongly recommended that producers prohibit any access by poultry to open water on the property.
It is also strongly suggested that producers work with local and federal agencies to develop the best way to deter wild birds from congregating on or near their farm. Specifically, in Missouri, the implicated farms have reported numerous geese on farms that are migrating north in the Mississippi flyway.
Best Farm Practices
The primary route of delivery for the avian influenza virus is through infected feces, and there are numerous methods through which even small amounts of feces can be transmitted into a poultry house. Producers should carefully practice the basic rules of biosecurity with visitors, vehicles and vermin:
1. Visitors and farm employees: Any visitors or employees must take extreme precautionary measures during these times. Visitors must wear disposable or washable coveralls, hairnets, and boots. Boots should be either disposable or made out of a material that can be easily washed and disinfected from house to house and from farm to farm. Visitors should avoid contact with wild and/or non-commercial flocks prior to visiting the farm. Employees should also remain aware of their clothing and evaluate their boot cleaning and disinfection protocols during this time to mitigate risk of spreading disease.
2. Vehicles: All vehicles used on the premises should be cleaned and disinfected prior to entering the farm, and travel between farms should be limited. Any service vehicles should be parked away from houses and barns. One of the heightened biosecurity measures taken by one company included preventing tractors with tillers from entering poultry houses. Tillers are used to condition the litter but when there may be significant droppings from water fowl on the farm, this could serve as a mechanism for spreading AI into the poultry houses.
3. Vermin: Disease can be picked up outside the poultry house or farm by many common pests, and subsequently transported in where it can infect poultry. Producers must proactively maintain and modify their pest control programs to best combat insects, rodents and predators.
4. Training and re-evaluation of biosecurity protocols: All companies should be evaluating their risks and control measures. Company veterinarians should be interacting with service techs and farm personnel to identify risks based on the migratory water fowl and how to prevent feces from these fowl from entering poultry houses. Primarily, the mode of feces entering the house would be equipment and people. Once risks and control measures are identified, the information should be effectively communicated to all service techs and farm employees.
The final, and most important, prevention method is to practice good farm hygiene and to establish a culture of cleanliness. Understanding that biosecurity is a critical responsibility in bird health shared by each member of the production operation will ensure that best practices are followed and maintained. Should a producer notice any evidence of unusual mortality in their flock, they must immediately contact their staff veterinarian to conduct a test for avian influenza. Early detection and depopulation is key to containing an infection and ensuring indemnity. Multiple methods are available for addressing carcass treatment and removal, and this should be discussed with state and federal agriculture personnel to decide on the most appropriate plan of action.
The USDA has worked hard to communicate with countries importing poultry products to minimize trade restrictions as a result of avian influenza detections. The Department's efforts have allowed trade to remain largely open, with the majority of restrictions at the state or county level. Communication from the poultry industry has helped to alert the USDA to any restrictions being enacted without formal government notice. Continued cooperation on the part of the poultry industry, and local, state and federal governments will guarantee that spread of the virus is contained and robust trade is resumed as quickly as possible.
USPOULTRY is making available its “Infectious Disease Risk Management: Practical Biosecurity Resources for Commercial Poultry Producers” program. The program was created to aid in developing more effective biosecurity practices and is designed to be used as a program development tool for personnel training and teaching.
The program is interactive, very user-friendly and includes educational videos and content, including an introduction video. The program is a multi-purpose, reference, employee training and teaching resource tool. This program is available to USPOULTRY members, free of charge. The program can be ordered by clicking here.
2 Alexander, D.J. An overview of the epidemiology of avian influenza. Vaccine. 2007. 25: 5637-5644.
3 Pomeroy, B.S. Avian influenza in the United States (1964-1980). Proceedings of the First International Symposium on Avian Influenza, 1981. 1982. 13-17.
4 Webster, R.G., Yakhno, M., Hinshaw, V.S., Bean, W.J., Murti, K.G. Intestinal influenza: replication and characterization of influenza viruses in ducks. Virology. 1978. 84: 268-276.