June 1, 2015: Update on Avian Influenza in the United States

By Anne Lichtenwalner, DVM, PhD, University of Maine Cooperative Extension

Since late last year, a real problem for poultry producers has arisen in the United States: highly pathogenic avian influenza (HPAI). In late 2014, following a cluster of cases in southwestern Canada, HPAI (contagious bird flu) was isolated from birds in backyard poultry flocks in Oregon and Washington. Since then, the disease rapidly spread from the northwest to other western, southwestern and Midwestern states. No HPAI has been found in the Eastern US so far, however.

wild ducks and geeseIn general, migratory wild birds — ducks and geese in particular — are the source of these viruses. If your flock is free-ranging, or if the feed or part of the flock’s enclosure is exposed to wild birds, your flock may be at risk. As well, being near larger poultry farms with HPAI, or near bodies of water where large flocks of wild birds congregate, appears to enhance the spread of HPAI to other flocks.

Wild birds migrate along “flyways”: these are generalized, vague “routes” that groups of birds tend to follow from south to north in spring, and back again in the fall. So far, HPAI seems to be showing up along the Western, Central and Mississippi flyways — but not yet on the Eastern flyway. It is unclear as to exactly why this is, but since HPAI can be carried by wild birds without killing them, it’s not unlikely that Maine could be at risk again in the fall. Some predictions have been made that suggest we will see increased risks of HPAI in the US for several years to come.

Most discussions of the current outbreak seem to indicate three things: that basic biosecurity helps to reduce spread of HPAI; that once a very large amount of virus is nearby (for instance, due to large, concentrated infected groups of birds shedding the virus) airborne spread may carry the virus as much as a couple of kilometers; and while heat will help to kill AI, warm weather is not going to wipe it out.

The good news is that there is no known human disease associated with the strains of HPAI currently in the US. However, other strains of bird flu in countries such as Egypt are causing problems, although there are only a low number of cases, and the disease is not spreading within the human population. In the US, where poultry workers are exposed to a high concentration of the virus, public health officials are advising that workers be careful to report any flu-like illness to their physician, just to be safe.

What does HPAI look like in birds? In general, it causes sudden death, and the symptoms can be a mixture of things: respiratory illness, which may or may not be accompanied by diarrhea. In the current outbreak, often birds die very suddenly without any particular illness. We strongly recommend that, if you have unexplained losses of birds or a severe decrease in productivity, you have your flock tested for HPAI. Contacting the Maine state veterinarian, Dr. Michele Walsh at 207.287.7615, is a good first step. The state may be able to pay for diagnostic work, including necropsy or blood testing for your birds.

As of the beginning of June, the USDA’s Animal and Plant Health Service (APHIS) estimates that over 200 poultry premises are affected with HPAI; with over 7 million turkeys and 40 million layers/pullets dead because of the disease or due to eradication efforts. The broiler industry is not yet considered to be affected by HPAI, but for the US turkey and layer industry the losses are getting close to 10% of the US industry. APHIS has spent over $150 million for active indemnity so far, and congress has authorized over $300 million to help defray HPAI losses to industry. Proportionately fewer backyard flocks are affected, and it is unknown if these are more resistant to the virus, or if fewer are reporting the problem. While it’s possible that the current strain affects commercial birds more severely, it’s prudent for all producers to reduce the risk by using excellent biosecurity.

Currently, the turkey and layer industries in Minnesota and in Iowa are epicenters of HPAI in the US. During mid-April to May, the number of active cases peaked at 36; in early June there are only 16 actively infected premises. APHIS has been able to depopulate turkey flocks within 36-48 hours of detection, speeding up their ability to disinfect farms and thus decreasing the likelihood of spread.

APHIS is depending heavily on composting to dispose of carcasses; it’s difficult to get landfills to accept large shipments of dead birds, and onsite burial is opposed by most farmers. APHIS just set up a large incinerator in Iowa to deal with carcasses; dead birds are contained in bags and “roll offs” until incinerated, which reduces viral load even prior to incineration.

While there are many EPA registered antiviral agents that may be effective against HPAI, APHIS seems to be relying most on Virkon, or on a hydrogen peroxide-based product. Disinfecting very quickly is probably an important factor in limiting spread. For very large farms, biosecurity must be very tight during the clean-up phase: it can take several weeks to completely clean up a large layer facility. Careful attention need to be paid to worker disinfection as they leave the worksite in order to avoid further spread of HPAI.

The question of HPAI vaccination is still being debated. APHIS is still accepting comments from industry, since use of a vaccine may not be protective. In general, the best approach is still the simplest one: biosecurity. Keep wild birds away from your birds. Key concepts:

  • AI virus is very concentrated:
    • 1 gram of manure could carry enough virus to infect 1 million birds
    • Disinfect boots/hands/tires
  • AI virus is very durable
    • Survives 1 week at 68° F
    • Survives 35 days at 40° F
    • Survives indefinitely when frozen
  • AI virus is primarily transmitted via feces, water, respiratory
    • Reduce aerosols: keep sick birds out of the house
    • Protect your face
    • Barriers between cages at shows/fairs: plexiglass
    • Clean boots, tires, floor of vehicle
  • Remember: Biosecurity is a series of multiple barriers, each reducing the risk of spread.

For more information and suggestions on biosecurity, please see the following: