Animal health: Influenza
Learn about the disease causes, clinical signs, treatment, prevention, management and potential transmission.
Overview
Influenza is a viral respiratory illness that can affect several wild and domestic animal species, including:
- poultry
- wild birds
- livestock
Influenza is not a threat to food safety for humans.
Influenza A
There are 4 types of influenza virus: A, B, C and D.
Influenza type A virus is important to be aware of due to its ability to infect different animal species and humans.
Most influenza A viruses infect a single species, while others can infect more than one species (such as birds, wildlife, cattle, pigs and humans).
Wild birds are:
- the primary natural reservoir for most subtypes of influenza A virus
- a source of influenza A virus infection for other animals
Outbreaks of influenza A can occur suddenly and spread rapidly, although sometimes the disease is extremely mild.
Subtypes
All influenza A viruses are further divided into subtypes based on 2 proteins located on the surface of the virus structure:
- hemagglutinin (H)
- neuraminidase (N)
There are 18 different H subtypes and 11 different N subtypes that can combine, change over time and lead to the development of new influenza subtypes in rare instances.
H5N1
Influenza A subtype H5N1 is a type of highly pathogenic avian influenza (HPAI), commonly known as “bird flu.”
It can affect domesticated and wild birds. It has been found in some wildlife and mammals, including livestock in North America, such as:
- lactating dairy cows
- goat kids
In rare circumstances, the virus can be transmitted from animals to humans. There are no known cases of H5N1 occurring in humans in Canada.
The spread of influenza can be prevented through strong biosecurity measures.
Clinical signs
Birds
Avian influenza A viruses are described based on the severity of the illness they cause in domestic birds.
Low pathogenic avian influenza A viruses (LPAI) target respiratory and digestive tracts.
Clinical signs include:
- depression
- appetite and weight loss
- ruffled feathers
- reduction in egg production
- low mortality
Highly pathogenic avian influenza A viruses (HPAI) affect all organs, including respiratory, digestive, reproductive, nervous and urinary systems, leading to systemic disease.
Clinical signs include:
- a drop in egg production with abnormal-shelled eggs
- coughing
- sneezing
- depression
- diarrhea
- purple-blue discolouration of comb and wattles
- neurological signs
- high mortality
Learn more aboutavian influenza in poultry.
Cattle
Lactating dairy cattle can be susceptible to HPAI (H5N1), though the severity of disease caused is not the same as with infections in domestic birds.
Cattle infected with HPAI have been reported to show mild signs, with only a small proportion of the herd being affected. Older cows and cows in later lactation may be more likely to present with illness.
Lactating dairy cattle infected with HPAI may not have any clinical signs. If they do, signs present as:
- decreased milk production
- thickened or colostrum-like milk
- decreased feed intake and/or drop in rumen motility
Secondary signs may include:
- dry manure
- constipation
- diarrhea in rare instances
- low grade fever
- secondary infections (including pneumonia)
Most affected cows appear to recover from the infection within 2 to 3 weeks.
It is not known if other types of cattle (such as beef cattle or youngstock) are susceptible to HPAI at this time.
Pigs
There are 3 main subtypes responsible for influenza A infections in pigs (H1N1, H1N2 and H3N2), with multiple strains within each subtype.
Influenza infection in pigs typically presents either as a severe (acute) respiratory disease or as an ongoing (chronic) form that affects mostly growing pigs.
Clinical signs include:
- fever
- depression
- nasal and ocular discharge
- cough
- short or laboured breathing
- loss of appetite
Most affected animals recover from the disease within 1 to 3 weeks, but weight drop in affected pigs may be significant, resulting in economic loss.
Equine
Equine influenza is caused by 2 subtypes of influenza A virus (H3N8 and H7N7).
Clinical signs include:
- fever
- nasal discharge
- dry cough
Sporadically, influenza can cause pneumonia in young foals and donkeys, as well as encephalitis in horses.
Dogs
There are 2 known strains of influenza A that more commonly infect dogs (H3N2 and H3N8).
The signs of infection can range from mild to severe, with severe disease more likely to occur in dogs with other illnesses or respiratory problems.
Clinical signs include:
- coughing
- sneezing
- nasal discharge
- ocular discharge
- loss of appetite
- fever
Most dogs recover fully within 2 to 3 weeks, with an ongoing cough that can persist after the virus has been eliminated.
Treatment
Producers concerned about HPAI in domestic birds or livestock should contact their veterinarian.
Veterinarians concerned about possible cases of HPAI should contact their local Canadian Food Inspection Agency (CFIA) animal health office for further guidance and consult CFIA’s guidance for private veterinarians on HPAI in cattle.
The response to influenza depends on the subtype and animal species involved. This is why testing is performed to identify which strains and subtypes are involved in a particular detection.
Livestock diagnosed with influenza may need supportive care with adequate rest, food, water and bedding or shelter. A veterinarian may prescribe medication to help control secondary infections.
To prevent the spread of the disease and to limit the economic impact of HPAI, government regulatory response to detections in domestic poultry may include:
- establishment of quarantines and zones
- ordering humane euthanasia of infected birds
- disposal, cleaning and disinfection
Prevention and management
Reducing influenza circulation in animal populations is important. The more widespread the virus is, the greater the risk of recombination with another influenza strain — this could result in the formation of a more serious influenza strain.
Strong biosecurity practices remain the most important measure to prevent the introduction and/or spread of all influenza A viruses in animals, including HPAI.
The Biosecurity Enhancement Initiative provides funding opportunities to agriculture industry businesses to support resiliency by addressing biosecurity risks.
Work with your veterinarian on biosecurity plans and training
- Have a veterinary-designed or reviewed biosecurity program in place with measures that include cleaning, sanitation, and segregation.
- Conduct adequate training of farm and company personnel in biosecurity and disease prevention.
Contact your flock or herd veterinarian for support on biosecurity planning, training and/or implementation of the practices listed in this section.
Proper management of people on your farm
- Ensure that laneways are restricted and secured.
- Limit non-essential visitors and provide clean clothing and footwear for visitors who must come on to the farm.
- Prevent the introduction of contaminants to animals in different barns by farm staff by providing dedicated clothing and footwear for each barn.
- Ensure people avoid direct contact with sick or dead wildlife, stray animals or wild birds. If you must handle wildlife, follow the guidance on protecting yourself when handling sick, injured or orphaned wildlife.
- Ensure people wash hands and cover their mouth when coughing and sneezing. If a farm worker develops an influenza-like illness while working with infected animals, they should immediately seek medical attention.
Proper management of farm equipment
- Properly disinfect equipment between uses on different animals on the same farm.
- Avoid exchanging and sharing equipment with other production sites or farms.
- Disinfect trailers and any equipment coming from other farms prior to use.
- Ensure all vehicles and farm equipment that access the barn vicinity are properly washed, disinfected and thoroughly dried before use.
Reduce or eliminate exposure to wildlife
- Prevent wild bird and rodent entry to barns and related facilities.
- Ensure that bedding is free of contaminants (such as feces from wild animals).
- Keep all domestic poultry indoors during the high-risk period of spring and fall migration.
- Report sick or dead birds, or other wildlife on your property, to the Canadian Wildlife Health Cooperative who may arrange for submission of wildlife for testing at the University of Guelph’s Animal Health Lab.
Manage interactions between new animals or multiple species
- Avoid events where animals from different locations are brought together, including shows, fairs, swaps, sales, educational programs and sporting events. Commingling animals from various locations increases the risk of spreading diseases such as influenza.
- Avoid introducing animals from other herds, particularly of unknown or suspect health status. Discuss with your veterinarian and consider pre-movement disease testing of animals prior to movement.
- Separate (quarantine) all new or returning animals to the herd for 3–4 weeks and monitor their health status.
- Milk new or returning dairy animals after the resident herd, and sanitize milking equipment before using on other groups, as influenza virus can be present in the milk of infected dairy cows.
- Avoid housing multiple species together.
- Apply biosecurity measures between species groups housed on the same farm.
Proper management of sick and young animals
- House sick animals with clinical signs in a designated sick pen, and contact your veterinarian.
- Change or disinfect footwear and clothing after attending to animals in the designated sick pen and milk animals in this group last.
- Feed only heat-treated colostrum and pasteurized milk or milk replacer products to calves and/or other animals on farm, as influenza virus can be present in the milk of infected dairy cows.
- In some species, vaccination can help minimize clinical signs and reduce the spread of the disease. Booster vaccinations are recommended regularly to help maintain protection against the disease.
Transmission to humans
Influenza (including HPAI) is not a threat to food safety. However, you should always:
- use proper cooking times and temperatures with poultry, meat and eggs
- user proper food handling techniques
- ensure milk is pasteurized before you consume it
People who work with poultry and livestock
Although transmission is rare, those who work directly with poultry and livestock are at risk of exposure to animal strains of influenza.
This includes people who:
- have occupational exposure to potentially infected livestock or poultry, carcasses, feces, litter, raw milk or surfaces and water that may be contaminated with animal excretions from potentially or confirmed infected animals
- work in environments where splash or aerosols will be generated (for example, using high pressure hoses or in ponds, or where people working at slaughter plants are handling live livestock or birds)
- work in an area where influenza has been diagnosed in livestock or wild birds
Take additional precautions and follow all public health guidelines. The World Health Organization and Health Canada have several recommendations to reduce the risk of exposure.
Flu vaccine
We strongly recommend that all people working with livestock or poultry to get the annual human influenza (flu) vaccine, especially those who work with birds or pigs.
The vaccine is free to all residents who work, live or attend school in Ontario, including:
- poultry and livestock producers and their employees
- veterinarians
- abattoir workers
- people handling wild birds
Contact your local public health unit for more information.
Infection control measures
HPAI
It is uncommon for HPAI to impact human health. To date, a very small number of isolated cases of human infection from HPAI have occurred worldwide, but no sustained human-to-human transmission has been reported.
However, reducing influenza circulation in human populations is important, as the more widespread the virus is, the greater the risk of virus changes or recombination with other influenza strains. This could result in the formation of a more serious influenza strain.
For farms where HPAI has been detected, farm workers will need to use different types of personal protective equipment (PPE) to reduce their risk of exposure, such as:
- fit-tested and seal-checked respirators (N95 or equipment with equivalent protection)
- eye protection (such as tight-fitting non-vented safety goggles)
- rubber gloves or disposable gloves (such as latex or nitrile) for cleaning and sanitation procedures and heavy-duty rubber gloves when handling birds that can pierce skin with beak or claws
- impervious disposable gown or coveralls
- disposable protective shoe/boot covers or rubber or polyurethane boots
Outbreaks on farms
People who work with poultry and livestock or in their environments should contact their local public health unit for recommendations for PPE for HPAI and follow all public health guidelines. In an outbreak situation, farmers with any species of livestock can order necessary PPE for free from Supply Ontario by emailing sco.supplies@supplyontario.ca.
If HPAI has been detected, your local public health unit will contact workers and anyone else potentially exposed on the farm to provide them with more information on what to do to protect their health. This includes:
- how to monitor for symptoms
- how long to monitor for symptoms
- who to call if any symptoms develop
Public health units may:
- check in over the monitoring period to determine if any supports may be needed
- help people access influenza testing if symptoms develop
Exposed individuals may also be recommended to:
- get the seasonal influenza vaccine (depending on time of year)
- take antiviral medication as prevention
Antiviral medication may be provided for free for individuals without drug coverage.
All influenza strains
If you develop an influenza-like illness while working with infected animals, you should:
- immediately seek medical attention and mention your exposure
- notify your local public health unit
Contact your local public health unit for more information on infection control measures.
Reporting
All H5 and H7 influenza A subtypes are reportable diseases to the CFIA in all animal species under the federal Health of Animals Act.
Influenza A virus detections in any animal species in Ontario are immediately notifiable, and veterinary laboratories are required to report to the Office of the Chief Veterinarian for Ontario. The Ministry of Agriculture, Food and Rural Affairs monitors and responds as appropriate.