Milk Testing to Help Trace H5N1 Herds
REDFIELD, Iowa (DTN) -- Since the beginning of the H5N1 influenza outbreak in dairy cows in March, more than 860 herds have been affected. To trace herds affected by the virus, testing began this week on Grade A milk intended for pasteurization.
"We know currently the cases we are seeing are in California and Nevada as far as the dairy industry goes, but we want to be able to work toward having the dairy herd free of H5N1," said Patrick Gorden during an Iowa State University Extension dairy webinar.
Gorden is a professor at Iowa State University's College of Veterinary Medicine who specializes in dairy production medicine and has been involved with the team that developed the national milk testing strategy.
"This testing strategy will allow us to determine individual state status with the goal of having freedom of H5N1 in the U.S. dairy population," he said.
STRATEGY FOR FREE STATUS
Gorden explained testing began this week to determine the presence of the virus in milk samples from bulk tanks at milk plants in 13 states. Milk is regularly tested at these plants, and now a sample will be sent to the National Veterinary Services lab in Ames, Iowa, for H5N1 testing. The bulk tank units could be from one dairy or multiple dairies. Each plant keeps track of where the milk comes from, which will help to trace any problems more easily.
"If a tank is found non-negative, the plant will work with the state veterinarian and the USDA within that state to collect samples from each of the dairy farms that went into that individual silo. Those tests will be sent to the diagnostic lab for that state. The state where that dairy is located will then become an affected state," Gordon said.
The National Milk Testing Strategy has five steps, which begin with national plant monitoring. Stage 1 involves milk silos at dairy processing facilities being tested. This will allow USDA to identify where the disease is present, monitor trends and help states identify affected herds. During Stage 2, state status is determined based on the results of the silo monitoring. This will allow for identification of herds affected by H5N1. Stage 3 will work with affected states to identify the cases and implement rapid response measures. This includes enhanced biosecurity using USDA's existing incentive programs, movement controls and contact tracing. When states are ruled unaffected through the testing, they move to stage 4, where regular sampling of farm bulk tanks continues for a time and then progressively declines as the state demonstrates continual silo negativity. If a state becomes affected, it returns to stage 3. Finally, stage 5 is when all states have moved through stage 4, and the entire country demonstrates freedom from the H5N1 virus.
Gorden said initially there will be four rounds of testing with milk samples collected approximately once per month, and then no more than four times every six months.
"You will see a map on the USDA website, similar to what has been used to show states with cases. It will show the affected or unaffected status of the individual states," he explained. "Hopefully, as the testing continues, we will see more and more states in stage 4. USDA thinks this will be a two-year process to get the country to stage 5."
POULTRY CASES SEASONAL
As a seasonal increase in highly pathogenic avian influenza is seen in poultry across the country -- especially in Iowa -- Iowa State University Extension Poultry Veterinarian Yuko Sato said the strain found in poultry is from migratory birds and is not affecting cows.
"Iowa is in the Mississippi flyway, and birds are congregating here. Over time, if you look at where the birds migrate, you see peaks during the springtime and again in the fall and wintertime," Sato said. "By looking at the BirdCast website (https://birdcast.info/…) we can see there are a lot of birds in the air right now. Yesterday there were 9.6 million birds in flight in this area. The big question we ask scientists is how this virus has been created."
Sato points out that the virus in cattle, which is identified as HPAI H5N1 clade 2.3.4.4b, genotype B3.13 is different than the current virus in poultry, but it's still an avian influenza. While strains have been known to pass from one species to another, it's most common when they share the same facility and have a common water source.
"That seems to be the recipe for disaster. Will it happen again? You know, I don't have a magic eight ball, but it's a freak event. And how many freak events can happen," Sato said.
Iowa has seen H5N1 cases in dairy cattle on 13 premises in 2024. Meanwhile, the number of poultry facilities fighting the virus is higher. Iowa State Veterinarian Jeff Kaisand said that in the past couple of weeks, HPAI has been detected in one backyard flock, four laying facilities totaling 6.6 million birds, and three commercial turkey farms totaling around 106,000 birds. The birds at these facilities have been depopulated and disposal is underway on the sites.
"This has been a difficult situation. The positive poultry sites have complete depopulation. The positive dairy sites don't have depopulation, but do lose production," Kaisand said. "And each state is different in how they treat a positive site. The one thing we all are the same on is the need to have good biosecurity measures." In Iowa, all positive tests are required to be reported. A control zone is then set, and tests are done on additional farms in the area zone. This has led to a few more positive cases.
TESTING HAS STARTED
Testing started this week on all Grade A milk intended for pasteurization in Iowa, according to Jurgen Ehler, bureau chief for the Iowa Dairy Products Control Bureau. Ehler said his team has the responsibility to keep farms, processing plants, haulers and anything involved with the movement of milk up to the distribution point in accordance with FDA and USDA protocols.
Iowa has 25 facilities that meet the requirements for testing and are either receiving or redistributing milk intended for pasteurization.
"The goal within our department is to sample approximately 110 samples per month," Ehler said. "The goal is to allow my staff to continue what would be routine monthly regulatory sampling and add this component to it."
Samples are taken from silos and recorded which bulk tanks are associated with the silo. Where the milk has come from in each bulk tank is recorded and can be traced to each farm. This is all recorded on the submission form. A positive test will be reported to the state veterinarian. Gorden said the results from the samples can be found in five days and will be recorded and displayed on a map on the USDA website. The testing is only on Grade A milk destined for pasteurization, which he said is close to 99% of the cow's milk in production.
"We want to be sure everyone knows this is an animal health issue and not a human health issue," Gorden said. "Pasteurization is an effective way to kill the virus." He said raw milk consumption is different. In Iowa, dairies in the raw milk program must have health tests performed on the cows and consult with a herd veterinarian annually. California has been testing raw milk diaries for the flu virus since May.
"I think dairy producers can control their own destiny. They need to make sure biosecurity is in place on farms to protect against this virus," Gorden added.
If a producer suspects a problem on their farm, they should contact their herd veterinarian or the state veterinarian.
If dead birds are seen, in Iowa, contact wildlife management staff at: https://www.iowadnr.gov/…
Jennifer Carrico can be reached at jennifer.carrico@dtn.com
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