Avian influenza (AI) cases have been popping up across the world recently, prompting many regions to implement disease prevention strategies and heighten biosecurity requirements on farms.
AI is known to spread in wild birds mainly along the wildfowl migration flyways, and the virus appears to be spreading more efficiently via migratory birds than ever. By travelling across the wildfowl flyways, AI can spread across the globe.
This map created by poultryworld.net provides a good visual of where high pathogenic AI cases are occurring and offers more information on each outbreak, including species, virus type, and date of reporting to the World Organization for Animal Health (OIE).
Given the current situation globally, this serves as a good reminder for the Canadian poultry industry that the risk of AI is very real.
Biosecurity is the Best Defense
The best defense against AI and other pathogens, as always, is good biosecurity:
Clinical Signs of Avian Influenza (AI)
Avian influenza (AI) is a contagious viral infection that can affect several species of poultry, such as chicken and turkey, as well as pets and wild birds. AI viruses can be classified into two categories – low pathogenic (LPAI) and high pathogenic (HPAI) – based on the severity of the illness caused in poultry. HPAI viruses typically cause severe illness and mortality, whereas LPAI viruses typically cause little or no clinical signs. Most AI viruses are low pathogenic; however, some subtypes are capable of becoming highly pathogenic1.
Birds affected with AI show a variety of clinical signs that may involve the respiratory, digestive, reproductive, or nervous systems.
Clinical signs of LPAI are typically mild and include:
Clinical signs of HPAI include:
Producers must be aware of the health status of their flocks and should consult their veterinarian upon any abnormal activity, clinical signs, or other concerns.
North America’s Waterfowl Flyways
There is evidence that the north-south migration of birds in North America within these geographically-based flyways plays an important role in shaping the genetic structure of populations of avian influenza viruses2. These flyways overlap and also allow the transmission of AI across North America.
The transmission of AI from wild birds to commercial flocks is a reminder for producers to be extra-vigilant during migratory seasons.
Image from Ducks Unlimited. www.ducks.org.
AI is not a food safety risk
There is no evidence to suggest that the avian influenza virus can be transmitted to humans through the consumption of food, notably poultry and eggs3,4. Follow the usual precautions when handling or eating poultry products: Wash hands and surfaces often, keep raw poultry separate from everything else, cook to a safe internal temperature, and chill leftovers within two hours.
What to do if you suspect AI on your farm
Upon suspicion of AI, producers in collaboration with their veterinarian should:
CFIA staff will visit your farm to begin an investigation and implement a quarantine (also called a Declaration of Infected Place) to control the potential spread of disease. Documentation will be provided outlining the rules of the quarantine, and any other farms with significant links may also be place under quarantine.
Wear personal protective equipment (PPE) when going into a suspect or confirmed barn with AI, or dealing with mortalities from those premises.
What to do if your farm is under quarantine
While your property is under quarantine, you will have the following responsibilities5:
Testing will be done as quickly as possible to confirm if the birds are infected with AI. Samples will be taken from the flock and sent to a CFIA-approved laboratory.
What happens if AI is confirmed on your farm or on a neighbouring farm?
CFIA has a webpage which details the steps that will be taken if your flock is infected with AI.
While all disease response situations are different, the steps involved in an AI response usually include the following:
The response to any AI diagnosis is led by CFIA and guided by their AI Hazard Specific Plan, which describes the principles of controlling the disease, defines the different control zones used for containment, and describes actions that can be taken in the vicinity of the Infected Place.
Upon confirmation of AI (H5 or H7), CFIA can implement several disease containment zones.
The above diagram represents a scenario with one infected farm. If additional farms are declared Infected Places, the sizes of the infected and restricted zones would change accordingly.
Infected Place: A premises where a CFIA presumes or confirms that AI exists.
Infected Zone: A minimum 1 km and up to 3 km zone surrounding an Infected Place. When possible, natural barriers and roadways will be used to facilitate the implementation of disease control procedures.
Restricted Zone: A minimum 10 km radius measured from the Infected Place that surrounds the Infected Zone. The boundaries will be defined by physical geographical barriers.
Security Zone: The geographic area between the perimeter of the Restricted Zone to the edge of the Primary Control Zone.
Primary Control Zone: An area established by the Minister to control a disease by regulating the movement of persons, machinery, animals, animal products and animal by-products. This area includes the Infected, Restricted and Security Zones and will be designed with the objective of controlling the spread of the virus and minimizing the impact on the poultry industry.
The above control zones are based on the standards in the Hazard Specific Plan, but CFIA may also implement different zoning depending on geography and disease pressures. For example, in some cases a 10km zone around the infected place may be implemented without the larger security zone.
Surveillance and movement on farms in disease containment zones
Depending on proximity to the Infected Place and the official diagnosis, farms within the containment zones may be required to submit birds for surveillance, to submit regular flock health data, and to conduct pre-movement AI testing prior to shipping live birds or moving eggs from a hatching egg flock.
Humane depopulation, disposal, and disinfection on infected farms
The CFIA has the mandate to humanely destroy any AI-positive or highly suspicious AI (H5 or H7) flocks and is responsible for carrying out these actions. Flocks will be humanely depopulated on farm, using carbon dioxide, other recognized mixtures of gas, or another approved method. To conduct a humane depopulation, extensive work will be required to thoroughly seal the barn.
All infected premises are required to be cleaned and disinfected, by the producer, under CFIA supervision according to CFIA protocols.
All flocks ordered to be depopulated by CFIA will be compensated as per the Health of Animals Act and regulations.
CFIA may compensate producers for:
Getting back to normal
While all disease response situations are different, the steps for repopulation usually include the following.
In the Control Area:
The release of individual Infected Place declarations can occur 21 days after the original declaration if all AI sampling at that farm has produced negative results.
The larger disease control zones will be maintained until at least 21days have elapsed since the cleaning and disinfection of all confirmed infected premises and negative results of surveillance activities.
After the zones have been released, surveillance activities may continue for 3 months in order to demonstrate to international trading partners that the virus has been eradicated. The OIE will only declare Canada an AI free region 90 days after completion of C&D and no further positive AI results.
Ongoing AI surveillance
This CFIA webpage details the programs in place to conduct regular AI surveillance that can act as an early warning system for industry. Surveillance programs occur in both wild life and within the commercial sector.
Wild bird surveillance is coordinated by the Canadian Wildlife Health Cooperative, while surveillance of the commercial sector is performed by the Canadian Food Inspection Agency through its Canadian Notifiable Avian Influenza Surveillance System (CanNAISS).
Links to other useful resources:
Weekly avian influenza updates from the World Health Organisation