Highly pathogenic avian influenza and biosecurity

Transcript

Christopher Lee, DVM, MPH, DACVPM: Yeah, I mean, the impact can be so dramatic, as we've seen when we look at soaring egg prices. A lot of that is due to limited availability and the fact that highly pathogenic avian influenza (HPAI) is running through the flock. When it does, you're looking at depopulation or euthanasia of thousands—sometimes even millions—of birds, depending on the virus. All of a sudden, it’s going to take quite a while to regain that population and get eggs back into circulation. So, when we consider that, much of the current epidemiologic focus—and the efforts to solve this issue—are really about limiting the spread within commercial poultry operations and backyard flocks. Unfortunately, nothing can be done about wild birds. They are the reservoir. Many congregate in the Arctic or similar areas, where commingling or even antigenic mixing of the virus occurs. When they return in the fall, you end up with a whole new set of influenza strains.

That’s when the challenge becomes clear. With this virus, you get both antigenic drift and shift. Drift is when the virus replicates, accumulating small genetic variations—less tightly controlled than in the human body. Shift, on the other hand, happens when two different viruses combine their genetic material; think of the two “S”s: shift and sharing. On the human side, when you add in pigs—with their similar respiratory receptors—they become a mixing vessel for dangerous strains. So while birds are the reservoir, in poultry the focus is on limiting spread.

As we discussed, one of my friends at the USDA helped coach me on some of this, since I’m not directly involved in protein production. Thank you to that USDA friend. When examining the main risk factor, much of it centers on surface water around poultry areas because it attracts waterfowl—the natural reservoir. Wild birds come to these water sources next to where other poultry is kept. Even in enclosed situations, people can act as fomites, carrying the virus on their clothing or equipment. Ultimately, it’s all about biosecurity: maximizing proper use of personal protective equipment (PPE), using dedicated boots and foot baths, controlling equipment movement between areas, and even limiting visitors. It’s damage control—minimizing spread rather than magically curing it, which isn’t likely in the near future.

I also think one of the big challenges lies with backyard producers. When you have a large flock and are trying to maximize production, it often comes down to money and numbers. Backyard producers want to partner up for help, as anything that minimizes costs now and prevents future outbreaks is beneficial. Backyard flocks can be particularly challenging; we’ve seen issues with Newcastle disease and HPAI. In backyard settings, chickens often have names—like Susie or Jill—so the term “depopulation” sounds very harsh when applied to them. A high-path HPAI outbreak might start with a few dead chickens and then progress rapidly. Chickens can go from mild symptoms to death very quickly—sometimes within a day or 36 hours. Before lab results (which may take a couple of days) come back, the flock may already have been depopulated. When we confirm it’s HPAI, it only confirms what we suspected.

Unfortunately, there isn’t a magic bullet. Every company keeps its R&D under tight lock and key, so while there might be something groundbreaking in the future, it doesn’t appear to be imminent. There has been some thought about natural immunity through selective breeding, which might offer benefits. However, selecting for one desirable trait can sometimes introduce an undesirable one. We’ve seen this in modern swine production, where pigs have been bred for rapid growth and heavier muscle at the expense of natural immunity. This might be an opportunity for the poultry industry, but it will take time. Much of the current focus is on upgrading biosecurity in poultry—an area where many operations could benefit from improvements similar to those in the swine industry.

Finally, regarding vaccines for poultry: to my knowledge, the only large-scale vaccination program currently in use is for ducks in France. A major reason is that unless everyone agrees it’s safe, vaccination could limit export ability. Even if vaccination became widely acceptable, influenza remains a moving target—constantly shifting, drifting, and undergoing antigenic mixing. That means new vaccines would need to be developed on a very rapid basis. There’s no easy answer.