By Lorraine Stevenson-Hall
Currently, there are 49 cases of dairy cattle infected with H5N1 highly pathogenic avian influenza (HPAI) in 9 states, with movement restrictions placed on lactating cattle in late April. In Canada, HPAI has not been detected in dairy cattle, but the country is requiring that lactating cows imported from the US have a negative test.
During a recent webinar hosted by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMARFA) providing an update on the situation, three things stood out:
- While more is being learned about how HPAI is spreading among dairy cattle, transmission routes are still not well understood.
- Limiting movement on and off farms is critical to prevent spread.
- Shared labour between farms and between species on a farm is a risk for spreading the virus.
During the webinar, Dr. Paul Innes, Manager, Veterinary Services at OMAFRA and Deputy Chief Veterinarian for Ontario, said that prior to its detection in March in a Texas dairy herd, the virus was not known to affect cattle.
Since the initial infection, most of the spread has been cattle to cattle through movements from infected herds. American government researchers say that genetic analysis shows the virus was passed from birds to livestock four months before it was detected, and this is one of the reasons it spread across the United States through cattle movements.1
HPAI was passed from birds to livestock four months before it was detected, and this is one of the reasons it spread across the United States through cattle movements.
“It’s spread from cow to cow through the milking process much like contagious mastitis”, said Dr. Innes. The U.S. Food and Drug Administration recently said that about 20% of milk samples from across the country tested positive for fragments of avian flu.2 While not a food safety risk provided the milk is pasteurized, high concentrations in the milk of infected cows indicates the virus is more widespread than initially thought.
Shared labour between farms and between species on a farm has likely been responsible for spillback of H5N1 from cattle to domestic poultry and wild birds. The virus has “spilled back to wild birds and domestic poultry, likely from shared labour and people moving from one farm to another and from one species to another on the same farm”, said Dr. Innes. The effects of H5N1in cattle are not well understood, but they are always severe in poultry.
As for biosecurity, he stresses that this is a very evolving situation and recommends limiting movement on and off the farm. New animal introductions, shared labour, and shared equipment are also areas where vigilance is needed to avoid spread.
The worst-case scenario is transmission to more cattle and beyond, leading to a wider epidemic in humans. Another risk is that countries may close their borders to American cattle products.
Dr. Innes concluded by saying that “The whole value chain has a role to play, not just farmers but industry organizations and processors.”
The detection of H5N1 in dairy cattle has highlighted the need to improve visibility and traceability of animal, people and vehicle movements between dairy farm sites. In addition, strategies to help protect against the potential for spread between human and animals are needed.
Digital technology can be a solution to enable dairy producers and co-operatives to quickly implement robust biosecurity protocols as both a preventative strategy and to speed up disease response in the case of an outbreak. Farm Health Guardian can help. Visit our website to learn more.
