Q&A: Could vaccinating birds, cows stop bird flu outbreak?
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Key takeaways:
- Bird flu has affected more than 97 million birds and 131 dairy herds in the U.S.
- The usefulness of vaccinating birds and cows remains under debate.
Avian influenza continues to be detected among birds and dairy cows in the United States, raising questions about how to control the more than 2-year-old outbreak.
According to the CDC, highly pathogenic avian influenza A(H5N1) — also called bird flu — has affected more than 97 million wild aquatic birds, commercial poultry and backyard flocks since January 2022, with more than 1,150 outbreaks in 526 counties across all 50 states. H5N1 has also been detected in 131 dairy herds in 12 states.
Four people in the U.S. have been infected with H5N1, including three this year — all of whom were exposed to infected dairy cows, according to the CDC.
We reached out to Maurice Pitesky, DVM, MPVM, BMEA, a faculty member at the University of California, Davis School of Veterinary Medicine-Cooperative Extension, to answer some of our lingering questions about H5N1, including whether it is possible to control the outbreak by vaccinating birds and cows. The answers have been lightly edited for clarity and length.
Healio: Are there vaccines to prevent H5N1 spread in bird flocks and cow herds?
Pitesky: Yes. The Chinese use them. The French are starting to explore them. We know from our COVID experience that vaccines are not a panacea, and there are scientific challenges. There are economic and political challenges.
Scientifically, the big issue is that, just like with COVID-19, the vaccines protect against disease but don't protect against infection. The worry is that you could have asymptomatic spread of the virus, and that can be dangerous. One of the nice things about clinical signs is that you know there’s an infection. We need to do necropsies on these birds to determine what's wrong with them because once we know that there's a problem, then we can really work on euthanasia, quarantine, the type of interventions that ultimately help prevent the spread of the virus. Those are the scientific and logistical or infrastructural-type issues.
On the political side, countries that vaccinate historically aren't allowed to trade internationally. The United States is a huge exporter of poultry products, mainly on the chicken broiler side. There are economic and political considerations there that are still kind of challenging. This outbreak is so significant that the powers that be are reconsidering that kind of generic policy. I don't think we've really finalized the minutiae on that but there definitely is some movement in that direction.
Also, the vaccines are good, but they're not perfect. The French have used them in ducks, for example, to some success and some failure. The question is: If you vaccinate, and you vaccinate again, and you still get clinical signs, what are you ultimately doing? What did you accomplish by vaccinating those birds if they eventually get infected with the virus?
Healio: Is it reasonable or possible to vaccinate entire flocks or herds?
Pitesky: Vaccination is easy; immunization is hard. Giving a vaccine in drinking water for 10,000 birds — or 1 million birds, even — is not easy, per se, but we do that a lot in the poultry industry.
Immunization is a little hard. We process 8 billion broiler chickens a year. There’s no way, logistically, that you can give them the two required doses. The logistics and economics of that is very challenging. When you’re dealing with that many broiler, that’s not trivial, and that’s expensive. And now companies and consumers ultimately are going to pay the price for that.
[For birds that lay eggs], there might be a little more of a push to do that because layer birds, they’re not producing eggs for about 20 weeks or so. There’s much more value that you would ultimately get in protecting those birds vs. a broiler chicken, as opposed to vaccinating maybe 50 or 60 days before it’s ultimately processed.
In my mind, and my bias with the work that I do, you really want to triage where you’re going to vaccinate and you want to understand where the risk is greatest. The main reservoir of the virus are wild waterfowl, like ducks and geese. You ultimately want to identify which locations are historically — and are forecasted to be — in the crosshairs of waterfowl habitat relative to these commercial poultry facilities. Then, companies can make a more nuanced decision about where they want to focus their vaccination resources.
Healio: Are farmers willing, or would they be willing, to participate in a large-scale national vaccination program, or even just disease surveillance?
Pitesky: Right now we’re dealing with something unprecedented, and farmers need help. Right now, the U.S. Department of Agriculture (USDA) is helping with all of their resources, money and labor on what happens after an outbreak. So how do we depopulate? How do we clean and disinfect these barns? How do we indemnify these farmers? They have relationships with the USDA, not as much the CDC, so they know these folks. The problem is that the USDA and state departments of agriculture are not putting enough into the front end of it, where we know that prevention is pennies on the dollar. I think there is absolutely potential to utilize and innovate and think more about how to reduce risk on the front end. We just haven’t had the kind of leadership in that area to really focus on some of these new approaches that probably are going to ultimately have some value. We’re using the same kind of playbook that we’ve used for decades on how to prevent outbreaks. The definition of insanity is doing the same thing over and over again and expecting a different result.
Ultimately, we probably need to dedicate more resources on the front end, and I think that’s where the farmers need help. I think we know that, but we just haven’t had that push toward innovation, technology and some of the newer ways we can prevent, understand, risk and triage. And then make decisions that are more science-based instead of saying all farmers need better biosecurity, because we’ve tried that and it’s really not working.
Healio: Do people with backyard chickens — whether they are pets, laying eggs or will be used as broilers — need to worry about bird flu either for their birds or for themselves?
Pitesky: The higher risk for backyard chickens is still boring old Salmonella, Campylobacter and similar types of bacteria that we can contract through contact with these birds.
But we obviously have dairy workers who were infected, so we have demonstrated that the virus can jump from birds to mammals, including humans.
My recommendation for anyone who has backyard animals is the same as it was before this outbreak: Be really cautious about contact, washing your hands and not touching your mouth or eyes or anything like that. Kids obviously are a little more likely to do these things. We just need to be real cautious. Anyone who is at risk or can’t exhibit those good practices probably shouldn’t have backyard livestock around.
Healio: What should clinicians take away from the ongoing bird flu outbreak in terms of caring for patients?
Pitesky: Poultry, right now, is the number one consumed animal protein on the planet, so I look at this from a security perspective more than I look at it from a public health perspective. The reality is humans have domesticated animals for about 7,000 years or so, not including dogs, and what we’re dealing with geographically — viruses on six continents — and species-wise is unprecedented in the history of agriculture. We’ve never had anything that’s this large before in every facet of an animal disease outbreak.
We need to be very careful. We need to put a lot of energy into trying to prevent this from getting any worse because it doesn’t seem to be going away, and I wouldn’t anticipate it going away at this point. We’re finding it in wastewater; we’re finding it in domesticated livestock, such dairy cows and chickens; and in all kinds of wildlife in places that we’ve never seen it before. So, it’s hard to imagine that it’s going away any time soon.
References:
- CDC. Avian influenza: H5N1 bird flu detections across the United States in backyard and commercial poultry. https://www.cdc.gov/bird-flu/situation-summary/data-map-commercial.html. Updated June 27, 2024. Accessed June 28, 2024.
- CDC. Avian influenza: H5N1 bird flu: Current situation. https://www.cdc.gov/bird-flu/situation-summary/index.html. Updated June 27, 2024. Accessed June 28, 2024.
- USDA. Avian influenza: HPAI confirmed cases in livestock. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/hpai-confirmed-cases-livestock. Updated June 27, 2024. Accessed June 28, 2024.
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