I have been remiss in not writing about the avian influenza outbreak currently going on among domestic poultry in the United States. Seanetter/physician Donna Cooper wrote to me on the subject of keeping you volunteers protected during your dealings with carcasses, and her prompt is much appreciated. Here is a bit of a primer on what’s been going on, and what precautions you ought to take.
Avian flu appears and recedes in the news all the time, so it can be difficult to know when big flu news is breaking. The current out break is most assuredly newsworthy, with millions of birds out west being culled in the face of the disease’s potential spread. Referring to a monolithic “avian flu” is misleading however. There are many sorts of bird flu, some causing little to no illness and spreading almost undetected in a bird population, and others causing massive and widespread mortality. The two main divisions used to categorize avian flu are LPAI (low pathogenicity avian influenza) and HPAI (high pathogenicity avian influenza). Seems fairly straightforward; LPAI=mild, HPAI=severe. Alas, it is not so simple as that. LPAI vs. HPAI refers only to the disease’s behavior in chickens in a laboratory setting. If an avian flu makes chickens very sick in a lab, it’s HPAI. If it causes no clinical signs or mild ones, it’s LPAI. This tells us nothing about how the disease would affect geese, ducks, other waterbirds, or even seals or humans, for that matter, and in fact, the same disease can profoundly afflict one species, which causing no perceptible issues in another.
(Left to right): USDA and APHIS scientists Dr. Catherine Woteki, Dr. Fidelis Hegngi, and Dr. Denise Brinson visit a backyard coop. These small operations are now on the frontline of disease monitoring and control. (photo: USDA APHIS)
Beyond the HPAI/LPAI division, we have the further H/N classification. You may have heard of the H5N1 bird flu causing fatalities in Indonesia and other countries a few years ago, or the H1N1 “swine flu” that laid many of us low in the epidemic of 2009. These Hs and Ns refer to proteins present on the virus’ surface that determine, in part, its behavior–how it gets into the body, how it invades cells once there, how severe its effects may be. Generally, though this is an oversimplification, the H5 class of avian flu are bad news and worth watching. These H5 viruses are exactly what government labs found when they tested wild birds found dead in the Pacific Northwest back in December. H5N2 and H5N8 were detected in a wild duck and a captive raptor, respectively. Virologists work to try and understand the family trees of viruses, and their work on these strains indicated that these viruses may be related to avian flu viruses previously identified in Europe and Asia, but to complicate matters, an H5N1 virus found in a wild duck in the U.S. in January of this year does not appear related to the H5N1s that have caused human mortality in Asia. This latter virus is what is known as “mixed-origin,” reflecting flu viruses’ general gift for mixing and matching genetic material when they encounter each other. That ability to “re-assort” and splice together bits of one variant with parts of another is part of what keeps us all vigilant about flu. If something like the Asian H5N1 bird flu, which presently can pass from birds to humans but so far has not been able to jump effectively between people, managed to acquire that skill, we would have the makings of a pandemic.
So, what of the goings-on in chicken houses throughout much of the country? LPAI infections have occurred from time to time in domestic poultry in the U.S. These strains are known to circulate in wild waterfowl in the U.S. True to their LP designation, these outbreaks may infect many chickens quickly, but cause only mild disease. HPAI in a poultry house, on the other hand, can be devastating. This year, H5 HPAI has been detected in backyard and commercial poultry, as well as in wild, migratory birds. You can see the latest numbers at USDA APHIS’ tracking site. The scale of the problem becomes apparent when you note the flock size listed in the far right column at that site–some of these chicken operations are raising over a million birds. Complete depopulation of these chicken houses after confirmation of HPAI infection is a daunting, though not unprecedented prospect. An outbreak of Exotic Newcastle Disease in poultry in 2002-03, for example, resulted in the euthanasia of over four million birds in the U.S. The numbers involved in the current HPAI outbreak are, admittedly, far higher and losses are ongoing.
Captive poultry are comparatively easy to control when we compare them with wild birds, however. We know that avian flu of various strains circulate in wild birds who can spread them throughout their migratory range. Waterfowl appear to be the major purveyors of the viruses, and can travel great distances. It may seem strange that a disease that so rapidly sickens and kills chickens and turkeys could be spread by wild birds apparently hale and hearty enough to fly the length of a continent. Part of the explanation lies back in the fact that not all birds are affected by avian flu the same way. HPAIs are “high path” in chickens, but the same virus often causes no disease at all in mallard ducks who may shed it in feces or respiratory secretions for two weeks after infection. And we have no data on the viruses’ behavior in the dozens of other species of waterbirds who may acquire the virus.
Waterfowl aggregration as petri dish? (photo: USFWS)
What to do? USDA and other agencies will continue to monitor both poultry and wild birds closely for new viruses, new reassortments, and new geographic occurrences of these HPAIs. So far, we are not seeing it here on the East Coast, but we should behave as if we may. Since you Seanetters handle dead birds as a matter of course, it’s a good time to review saftety practices that are good habits to maintain whether or not a flu outbreak is underway. The CDC’s full suite of recommendations for working with infected birds or carcasses of bird flu victims include goggles, gloves, coveralls, masks and the like. For our purposes, given that the CDC lists the risk of human infection from these H5s as very low, we will continue to recommend wearing gloves whenever handling a carcass for tagging or measurements, discarding the gloves after use, and washing hands thoroughly after the walk. As always, if you have a weakened immune system for any reason, you may be at increased risk of any infection, not just avian flu, and may wish not to handle dead birds at all. If this is the case, get in touch and we can figure out some accommodations. Should you find yourself ill, particularly with a respiratory illness, the CDC asks that you disclose any contact with potentially diseased birds to your doctor. Doctors (and vets, for that matter) are taught, “when hearing hoofbeats, think horses, not zebras.” Because of this, your doctor is unlikely to think of avian flu as a potential diagnose unless you disclose your exposure. Contrary to what we all may think, it’s not usual to muck around on the beach with dead birds. On the other hand, anyone who has walked on a soccer field or golf course has been exposed to more potentially infectious goose feces than the average Seanetter meets in a year of tagging carcasses, so do maintain a sense of perspective.
I hope this has served as a helpful outline of the problem, and not has not unduly alarmed you. Your risk of becoming sick from handling dead birds is extremely low, but particularly if any of you should happen upon a major mortality event involving waterfowl (the main species groups affected by these viruses) I wanted you to be informed participants.
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