Overview of HPAI (Bird Flu)
Highly Pathogenic Avian Influenza (AI), commonly known as Bird Flu, is an infectious disease caused by virulent subtype of type-A influenza virus that primarily affects birds. These viruses are naturally present in various migratory wild birds such as ducks, geese, swans, and shorebirds. While many migratory birds carry the influenza virus without experiencing illness, they can spread the virus over large geographical areas during their annual migration from colder regions to warmer areas in the fall and back to the North in the Spring season. In the continental United States, there are four main migratory corridors known as the Pacific, Central, Mississippi, and Atlantic flyways. Domestic poultry can be infected by these migratory birds, resulting in severe and often fatal illness. Although migratory birds serve as the primary reservoir for the virus, it can also spread rapidly among domestic poultry, and occasionally infect humans and other mammals. Influenza viruses undergo constant mutations, leading to the emergence of new strains and subtypes with unique characteristics. In recent years, the virus has expanded its host range to include ducks and geese. Overall, Avian influenza is a highly contagious and severe viral disease that poses significant economic and public health concerns for poultry populations.
Subtypes of Avian Influenza
Influenza virus can be classified into different subtypes based on the characteristic combination of two types of proteins found on the viral surface: hemagglutinin (H) and neuraminidase (N). So far, 18 different “H” proteins (H1-H16) and 11 different “N” proteins have been identified with 198 possible combinations. Each unique combination of H and N proteins is termed as a subtype of virus and can be further broken down into strains and clades. Many of these subtypes can be grouped into two categories based on their pathogenicity in domestic chickens: Low pathogenic avian influenza (LPAI) and highly pathogenic avian influenza (HPAI).
The influenza viruses of primary concern in poultry industry are of high pathogenic subtypes as they cause significant economic damage and distress to the commercial as well as backyard poultry producers. H5 and H7 subtypes of avian influenza virus are known to cause HPAI with few variations in “N” proteins. H5N1, H5N2, H5N8, H7N9 and H7N8 are the major HPAI subtypes which have caused significant Bird flu outbreak in the United States. HPAI is a notifiable disease, and all outbreaks must be notified to the World Organization of Animal Health (WOAH) by the authorities.
Signs of HPAI in Poultry:
Poultry growers should possess knowledge about the symptoms associated with deadly poultry diseases like HPAI. Being familiar with these signs enables them to identify any abnormalities or issues promptly. Early detection plays a crucial role in preventing the transmission of diseases. Be vigilant and watch out for the following indications:
- Sudden Spike in Mortality
HPAI is a highly fatal disease of poultry, especially chickens and can cause significant increase in bird deaths. If there is a sudden spike in mortality without any obvious signs, it could be indicative of HPAI.
- Respiratory Distress
Infected birds may display coughing, sneezing, wheezing, gasping, along with nasal discharge.
- Reduction in Appetite and Productivity
Reduced feed and water intake, weight loss, and sharp drop in egg production.
- Swelling and Discolorations
In a HPAI infected poultry, there is swelling and cyanosis of head, comb, and wattles.
- Neurological Signs:
Signs like twisted Neck, paralysis, or unsteady gait are also visible in infected Poultry.
- Watery and greenish diarrhea
For additional information, please refer to the USDA APHIS Defend the Flock Program
Protecting your flocks from HPAI inflection
Regular Surveillance and Biosecurity are essential in protecting your flocks from the high pathogenic avian influenza. Both commercial and backyard poultry producers can be greatly benefitted by the application of biosecurity in their premises as a properly documented implementation of biosecurity also helps with the claim of indemnity in case of HPAI outbreak. The need of proper biosecurity in place for the commercial poultry in Maryland is accentuated by the fact the Atlantic flyway, the wild-bird migration corridor bordering Atlantic Ocean goes through it.
Constant monitoring and surveillance of your flock for any unusual signs of illness or behavior and reporting the suspect cases is essential in controlling the outbreak. Sampling and testing the flock for avian influenza is also very important in controlling the further spread of avian influenza. Wild Bird management is another key approach in preventing the transmission of avian influenza from the migratory birds to your poultry flock. The poultry premises can be secured against the migratory birds by
- Habitat Management: Removing Standing Water, spilled feeds, removing the trees and vegetation covers.
- Installing Scare Devices: Installing scarecrows, reflective tapes, balloons, or auditory distress calls can discourage the visit of wild birds.
- Application of Nets and Fences: To prevent wild birds from entering the poultry housing and feed storage area, nets or meshes or fences can be applied where appropriate to close the open areas or gaps.
- Reporting: Reporting the constant detection of Wild Migratory Birds to the animal health and wildlife authorities and gather information on HPAI risks. Do not touch or move the birds and contact Department of Agriculture Wildlife Services at 1-877-463-6497
Reporting the Suspect HPAI infection in your Flock
If your bird shows any unusual signs resembling HPAI, do not wait and immediately report it. You can ask for Maryland Department of Agriculture state veterinarian at (410) 841-5810 or birdflu@maryland.gov
For more information about High Pathogenic Avian Influenza related news and policies, please visit this link.
Acknowledgment:
This work is supported by the Smith-Lever Special Needs Competitive Grant, project grant number 2022-41210-38062, from the USDA National Institute of Food and Agriculture and the University of Maryland, College Park. ( you can add logos for UMD and USDA NIFA as you see fit)
Project Title: Biosecurity Compliance Audits to Prevent Outbreaks of HPAI and Risk-Based Planning to Improve Outbreak Response.
Project Team: Dr. Nathaniel Tablante, Dr. Mostafa Ghanem,Dr. Jonathan Moyle, Jennifer Rhodes, and Maegan Purdue, Madhusudan Timilsina