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May 12, 2025
Minnesote Board of Animal Health
May 2025
Correction: an earlier version of this bulletin misstated what happened to the fifth lactation positive cow.
What we know about the state's only recent H5N1 dairy detection
The Stearns County dairy where H5N1 was detected in late March also had a detection of the virus in July 2024. The entire herd was affected during the summer 2024 case and milk production dropped with clinical signs noted. By September 2024 the herd had achieved three straight weeks of bulk tank tests with no virus detected and the Board released the quarantine. Milk production started to return to normal over the fall and winter months.
On March 16 a bulk tank sample collected for Minnesota’s milk surveillance program tested non-negative at the U of M’s Veterinary Diagnostic Laboratory and was later confirmed to be H5N1 at the National Veterinary Services Laboratories on March 21. Additional testing by the University was able to narrow down the detection to a single cow. The only cow on the farm to test PCR positive for the virus was a fifth lactation cow milking around 65 pounds of milk per day with no observed clinical signs. Additionally, the owner reported she was not sick during the summer 2024 detection and didn’t show any clinical signs over the winter.
The only major activity in early 2025 on the dairy was when heifer calves moved back into the herd in March. The other common avenues epidemiologists look into to determine how a virus infects a herd didn’t produce any strong indicators. The owner reports feeding calves pasteurized colostrum from a single cow and waste milk is not fed to calves. Sparrows and starlings are commonly spotted around the farm and near the feed with some evidence of small mammals. These animals are also sometimes reported around the bedding, which is stored on a separate farm until it’s brought in to freshen stalls.
The fifth lactation cow, which was the only animal to test positive for H5N1 was donated to the USDA for further testing to study the cow for duration of shedding and her immune response to the virus. No other cases of H5N1 have been confirmed in Minnesota since the start of the MDA’s milk surveillance program earlier this year.
Pasteurization inactivates the virus and all pasteurized dairy remains safe.
https://content.govdelivery.com/acco...letins/3e00752
Minnesote Board of Animal Health
May 2025
Correction: an earlier version of this bulletin misstated what happened to the fifth lactation positive cow.
What we know about the state's only recent H5N1 dairy detection
The Stearns County dairy where H5N1 was detected in late March also had a detection of the virus in July 2024. The entire herd was affected during the summer 2024 case and milk production dropped with clinical signs noted. By September 2024 the herd had achieved three straight weeks of bulk tank tests with no virus detected and the Board released the quarantine. Milk production started to return to normal over the fall and winter months.
On March 16 a bulk tank sample collected for Minnesota’s milk surveillance program tested non-negative at the U of M’s Veterinary Diagnostic Laboratory and was later confirmed to be H5N1 at the National Veterinary Services Laboratories on March 21. Additional testing by the University was able to narrow down the detection to a single cow. The only cow on the farm to test PCR positive for the virus was a fifth lactation cow milking around 65 pounds of milk per day with no observed clinical signs. Additionally, the owner reported she was not sick during the summer 2024 detection and didn’t show any clinical signs over the winter.
The only major activity in early 2025 on the dairy was when heifer calves moved back into the herd in March. The other common avenues epidemiologists look into to determine how a virus infects a herd didn’t produce any strong indicators. The owner reports feeding calves pasteurized colostrum from a single cow and waste milk is not fed to calves. Sparrows and starlings are commonly spotted around the farm and near the feed with some evidence of small mammals. These animals are also sometimes reported around the bedding, which is stored on a separate farm until it’s brought in to freshen stalls.
The fifth lactation cow, which was the only animal to test positive for H5N1 was donated to the USDA for further testing to study the cow for duration of shedding and her immune response to the virus. No other cases of H5N1 have been confirmed in Minnesota since the start of the MDA’s milk surveillance program earlier this year.
Pasteurization inactivates the virus and all pasteurized dairy remains safe.
https://content.govdelivery.com/acco...letins/3e00752
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