Avian influenza H5N1 — what we know so far about infecting cattle

Bird flu has been circulating for at least four years, causing large-scale outbreaks and killing millions of birds. It was later discovered in lumps. sea ​​lioncultivated mink, Catand other mammals.

Last month, highly pathogenic avian influenza A H5N1 was found to be spreading from the source, increasing the threat of human spread. From dairy products to dairy products and from dairy factories to poultry farms.probably I started earlier It wasn't discovered because it wasn't monitored more thoroughly.

In the United States, only two cases of human infection have been reported so far. At first he was in 2022. poultry workers In Colorado.

Since 1997, HPAI A(H5N1) 909 items It has been reported from 23 countries, mainly after exposure of poultry. More than 50% died. This high fatality rate may be an exaggeration because we don't know how many people have actually been infected. Notably, there was no sustained human-to-human transmission.

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In March 2024, dairy workers in texas I was found to be infected with HPAI A(H5N1), also known as H5N1 avian influenza. His only symptom was mild conjunctivitis, but he was treated with oseltamivir (Tamiflu). Currently, several states are reporting infections in dairy herds. In some cases in Michigan and Idaho, Transport of cattle from Texas was thought to be the origin.There are spillovers to various mammals, mainly wild fox and skunk. Cats infected on farms showed neurological symptoms such as seizures, and many died.

Avian influenza is also occurring in some parts of the country. top egg producers, a large-scale chicken farm in Michigan. Appropriate biosecurity measures are taken there, such as changing workers, leaving work clothes and boots on the farm, spraying shoes and car tires before leaving, and cleaning all trucks.

contagion; infection

Milk from infected cows has been found to contain particularly high amounts of virus. This suggests that the infection can be spread through milking machines or when the milking room is power-cleaned and infected milk is aerosolized. For this reason, workers must wear protective equipment.

Another big problem is how cattle in the United States are fed. poultry “waste”; This is a euphemism for leftover feathers, bird droppings, spilled seeds, and the occasional dead mouse or rat mixed in. If broiler bedding is not used, he has a period of 15 days before the cow is slaughtered. Dairy cows should not be fed bird litter because of this two-week “weaning period” before human consumption.

Cattle manure based on poultry litter is widely applied as fertilizer on fields, including on organic farms. Therefore, the entire agricultural supply chain may be at risk of spreading infection. At least in limited testing, cows do not appear to be shedding the virus through their feces.

There are other possible routes of infection. for example, house fly Blowflies can transmit H5N1 viruses and other avian influenza viruses. During the HPAI (H5N1) outbreak in Thailand in 2005, he mosquito sucking blood The patient collected at a poultry farm tested positive for H5N1 by reverse transcription-PCR. wind diffusion In the 2003 outbreak, it could explain up to 24% of infections at distances of up to 25 km.

It seems that the infection is spreading From cow to bird.Grackles, blackbirds and chickens all showed up. Mutations from mammalssuggest this route.

Compatibility gap

Government responses to this potential biological threat have been reactive and limited.

The strongest initial criticism was that the USDA did not fully share data, even though data and sample sharing is required as a basis for pandemic preparedness.When we finally share the genetic sequence Gisidean international database widely used by scientists since 2008, but the USDA does not disclose the origins of the samples and does not include critical timing data.

Another problem is that cattle testing is limited to dairy cows before they are transferred to other states. We don't know if beef cattle are infected.

Surprisingly, The government clearly had no power Restricting cattle movement and requiring testing and reporting of infected herds and workers.Several Farmers are reluctant to allow inspections. We know how voluntary reporting and regulation works…

However, on April 24, the USDA's Animal and Plant Health Inspection Service announced that dairy cows must: Tested before interstate shipping And labs and veterinarians would have to report if a cow tests positive. APHIS also announced that H5N1 was found in lung tissue samples from asymptomatic dairy cows in the affected herd.

One case of conjunctivitis was recently reported, but it is likely to be significantly underreported. There have also been case reports of workers exhibiting symptoms such as fever, cough, and fatigue. I don't want to undergo tests or see a doctor. Many workers are likely in the country illegally and do not trust the government. Dairy owners don't want to risk falling prices or culling their herds. Dr. Barb Petersen, a cattle veterinarian, said underreporting and fear exist. she told cattle veterinarian journalist Rhonda Brooks. “But every dairy farm I've ever worked at, except one, had sick cows and sick people,” she also reported. Infection of people who do not have direct contact with dairy cows. “I'm talking about owners and feeders who don't normally touch cows.”

However, a group of veterinarians called the American College of Bovine Practitioners proposed calling the virus: “Bovine influenza type A virus” Not because of bovine avian influenza, but because “we believe it is important for the public to understand the difference between cows and bovines.” maintain confidence We focus on the safety and availability of beef and dairy products for consumers. ”

Criticism of response

There has been considerable criticism of the slow response of federal agencies. For example, Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, told the Telegraph: USDA is primarily focused on protecting animal production That's a short-term goal, but I think it's a mistake in the long term. ”

Eric Topol, M.D., director of the Scripps Research Institute's Translational Institute, tweeted: @USDA's A pathetic lack of transparencyhow long it took for the genome to be published, and the lack of testing for asymptomatic cows…

All of this undermines “confidence.”

Dr. Rick Bright, a virologist, immunologist, and CEO of the Rockefeller Foundation Pandemic Prevention Institute, echoed these concerns, adding:Temporarily suspend milk intake while waiting for data. ”

Criticism has also been leveled at the lack of oversight, particularly of asymptomatic animals, beef cattle and farm workers. Farmworkers are generally young and healthy and are less likely to be treated in hospitals, where most surveillance is concentrated.

Dairy safety

Sick milk looks different, thickened and discolored. It should have been discarded, but it is clearly being distributed on the commercial market.

The FDA states that milk is safe through pasteurization and that infections from milk areNo worries,” critic Please note that the agency does not provide testing evidence.

A citizen science study was conducted in which researchers purchased 150 dairy products processed in 10 states at a grocery store in the Midwest.they found PCR tests detected virus fragments in 58 of the samples. Virus could not be grown from these samples. We are still awaiting FDA test results to confirm whether pasteurization kills the virus as expected.

H5N1 news is changing so quickly that it's hard to keep up. Brennan Klein, Moritz Kraemer, and SV Scarpino posted useful information. Timeline that it is updated frequently.

Finally, I'd like to share some good news. The Department of Agriculture monitors feral pigs. H5N1 has not been detected so far. Infection of pigs is a major concern because mutations in swine influenza viruses are most likely to infect humans.