If HPAI is suspected, producers should contact their veterinarian and isolate any sick animals from the rest of the herd. Private veterinarians are the first point of contact for HPAI in cattle. If a private veterinarian suspects HPAI, they must report to the CFIA. See Guidance for private veterinarians for more information on best practices and sampling.
HPAI is also reportable in some provinces and territories.
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Clinical signs of HPAI in cattle
Cattle infected with HPAI virus may show the following signs:
- decreased feed intake with a simultaneous decrease in rumination and rumen motility
- respiratory signs, including clear nasal discharge
- sudden and significant decrease in milk production
- colostrum-like consistency of milk in 1 or more quarters
- dry stool or diarrhea
- lethargy
- dehydration
- fever
Some cattle recover in 4 to 7 days, but milk production may not return to normal.
Veterinarians must report suspected HPAI cases to their local CFIA district office and where required, the provincial or territorial Chief Veterinary Officer.
A higher level of suspicion is based on:
- clinical signs consistent with HPAI and no other diagnosis
- contact with infected animals or herds
- new animals introduced to the herd in the past 30 days
- dead or neurologic animals on the premises (for example, cats, wild birds, raccoons)
- possible contamination of feed or water by wild animals
Transmission insights
- HPAI in dairy cattle in the United States (U.S.) started with a single spillover from wild birds in late 2023, followed by cow-to-cow transmission. Additional spillovers from wild birds into dairy cattle in the U.S. also occurred in early 2025.
- Research on transmission of HPAI between cows is ongoing. Spread between cows seems to be associated with milking activities. However, evidence suggests other transmission means such as nose-to-nose contact, oral and respiratory spread may also be important.
- Non-clinical animals can also shed the virus in their milk, making pre-movement testing important
- Many outbreaks are linked to the introduction of new animals from an affected area or herd.
- Contaminated equipment or personnel can also transmit the virus from dairy herds to nearby poultry flocks.
Biosecurity
Good on-farm biosecurity practices are always the best way to prevent the introduction of diseases on farm as outlined in the National Biosecurity Standards (Animal biosecurity). Dairy producers are required to adhere to biosecurity plans outlined in Dairy Farmers of Canada's proAction program.
General prevention tips:
- avoid bringing new animals onto the farm
- if dairy cows must be added to a herd, or if animals have had contact with animals from other herds (for example, a show or sale yard):
- test milk samples from lactating animals and a bulk tank test from the herd of origin within 7 days before arrival whenever possible
- isolate and monitor cattle for 21 days as per normal industry standards
- consider testing individual animals and the bulk tank between 14 and 21 after isolation prior to introducing these animals into the herd
- Only release animals from isolation after negative test results
- clean and disinfect livestock trailers after transporting animals
- prevent wildlife access to cattle, feed and water sources
Producers may wish to contact provincial or national associations for any enhanced biosecurity protocols that may be available.
Personal safety
While the risk to humans is low, those in contact with potentially infected animals, raw milk or environments should wear personal protective equipment (PPE).