David Swayne on Influenza: "You have to develop a very strong culture of biosecurity"

Published on: 3/3/2017
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Q: What are the essential measures to prevent avian influenza?
A: For most farming situations, the best way is to improve biosecurity on the farm, so that it is practiced every day. Make it a consistent habit, including admitting very few visitors to the farm. Anybody who comes on the farm would have to meet personnel and equipment biosecurity standards, for example, people would not go into the barn unless they were wearing clean new clothes and boot covers and when they leave, they would leave those clothes behind and also disinfect their boots. Showering on to the farm would be an additional biosecurity step.
Equipment coming in is another difficult issue, for example, not sharing standard farming equipment like front-end loaders or tillers, which handle litter contaminated with pathogens. That is the kind of thing that would move farm to farm that can easily move multiple pathogens, not just influenza.
Service trucks, people coming in to work on electric lines, plumbing, etc., those would have to go through the same biosecurity process. Of course, we see people commonly washing the tires, before they come on or leave farms, but probably more critical is making sure that their footwear has been properly disinfected; also the floorboards of the vehicle and other parts. It would take probably a good biosecurity risk assessment on the farm and all the practices to come up with a list of the things you can prioritize that needs to be done to improve biosecurity. And really by improving it, it is how farmers can keep the virus out, whether it is a low or high pathogenic influenza that maybe was brought in by migratory waterfowl, and it would keep it from going farm to farm.
Q: If there is an outbreak, what is the best way to contain it?
A: Those become more complex logistic issues of how to maintain good surveillance, which is samples coming off the farm, but then having good business continuity plans. Knowing how to manage large integrated processes in a company, for example, feed. How do you get it on and off the farm without risking spreading it from one facility to another? How do service personnel handle their particular jobs and tasks? When do they go on farms? When do they do not? You would need to know the status of the individual farms, as far as influenza, providing those surveillance samples to a lab, then the laboratory can turn it around and give you a rapid response whether this flock is infected or not and then how that changes the flow of materials from that company into that area. Those become really difficult challenges and takes good logistic coordination in the company, as well as between companies, to make sure that it is not spread by the normal activities of producing poultry.
Q: Could relaxation be one of the challenges, because cases are few and far between?
A: In general, on a farm and within a company, you have to develop a very strong culture of biosecurity to keep the pathogens out. And if we are concerned about avian influenza, particularly a highly pathogenic virus, which in the US we don't have, as we have eradicated all these viruses, over time you kind of forget about those viruses and all the devastation they can do. Also, maybe you forget how they can cause you to shut down a farm, not grow birds for a period of time and leave people without jobs. If you do not experience it, then it is human nature to maybe become lax on those biosecurity principles that are critical to keep it out. Really the challenge is how to maintain a high level of biosecurity, but not for just the sake of keeping out high pathogenic AI, but overall, those same procedures also keep potential exposure to any pathogens, which would have a long-term positive economic impact. For example, infectious bronchitis or infectious laryngotracheitis. The same principles apply in biosecurity in keeping those diseases out.
Q: What are the most dangerous strains of avian influenza?
A: For avian influenza, we are most concerned about the highly pathogenic avian influenza (HPAI) forms and there are only two subtypes that have been found to be highly pathogenic, H5 and H7, but on the same hand, we have to realize that just because it's H5 or H7, doesn't mean it is highly pathogenic, cause there are quite a significant number of low pathogenic H5 and H7.
Around the globe, since about 2005, there has been an agreed upon process internationally, this is supported by guidelines developed at the World Organization for Animal Health (OIE), that all H5 and H7 of low pathogenicity are also reportable and what this allows is then countries can develop rules for eradication of the low pathogenic viruses, H5 and H7, before they mutate and become highly pathogenic viruses. So this is being one step ahead of HPAI. If we can find these low paths 5's or 7's before they mutate, and we eliminate them as low paths, then we will prevent a lot of potential HPAI outbreaks by getting in that earlier.
And also there is one other step, even further to the left. Most low path AI strains are not H5 or H7, so we have a variety of other low path viruses, H1's and 2's and 3's, all the way up to H16, and those, of course, are more of an economic disease and it depends on where you are at in the world. As an example, H9N2 is the most common low pathogenic AI virus and those viruses, where they are endemic -and that would be in much of Asia, across India, the Middle East, Northern Africa and even some parts of southern Europe-, those H9N2 viruses also cause significant economic disease, even though they are not reportable and they are not eradicated by most countries, but they still have a huge negative economic impact and many of those countries use vaccination as a mean of controlling the disease. So you have lower mortality, less clinical disease, to the effect that low path H9N2 in many countries has become a common endemic viral disease that you control just like you would infectious bronchitis, or even Newcastle disease, by vaccination.
Q: In terms of developments of vaccines, what is the way to go?
A: With avian influenza, in endemic countries, mostly in the developing world, vaccination has been used as a major control tool, and H9N2 is the most widely vaccinated subtype, but in some areas like Mexico and Latin America, there is low path H5N2 and there has been a vaccine for more than 20 years. Then we have the highly pathogenic strains, the H5, we saw it in China 20 years ago, those are vaccinated across many countries in Asia and Egypt. What we have seen emerge over the past 10 years, where you use vaccination as a control tool in the field, you have to continually monitor the emergence of viruses that are resistant to the vaccine strain. So it is a moving target, we can never be happy with "oh, this is the perfect vaccine, it will last a lifetime".
We see now that after the use of a particular vaccine strain for several years, the field will experience the rise of vaccine-resistant strains, and you have to go back and update the vaccine to match those field viruses. This has been shown first with the high path H5 viruses in countries such as Indonesia, which has had a large vaccination program; China, which has made several changes in their vaccine strains; but also the need to change vaccine strains has been felt down to the level of the H9N2, where many countries have had to update their H9 vaccine strains to newer field viruses for better matchup in order to have influenza vaccination to continue to be an effective tool for control.
 Q: You also have a book called Avian Influenza, and now a second edition, entitled Animal Influenza.
A: I've had the privilege to work with many good influenza scientists and veterinarians around the world. In 2008, collaborating with many of them, we published a book called Avian Influenza, it was a very successful book and it helped veterinarians and poultry science professionals all over the world to better understand avian influenza and know how to control it.
I contemplated revising the book because a lot has happened in the last few years, and what I came to realize is that influenza was much broader than just avian, I mean, it is an ongoing disease problem in other species especially swine, horses, dogs and humans. There was a need out there to collect more information on multiple species. Wiley approved a second edition and we expanded it to be Animal Influenza. A third of the book is general information about influenza A virus diagnostics and the virology. Another 1/3 part is focused on avian influenza, which updated chapters from the previous book. And the last third of the book is all new material on influenza in mammals. 
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