Highly Pathogenic Avian Influenza in SD

Source: by SDSU iGrow

BROOKINGS, S.D. – This week, the South Dakota State University Animal Disease Research and Diagnostic Laboratory detected highly pathogenic avian influenza virus in samples submitted from a turkey farm in Beadle County. 

Higher than normal death loss in one of four barns on the premises prompted the caretakers to seek diagnostic assistance, explained Dr. Russ Daly, SDSU Extension Veterinarian, State Public Health Veterinarian & SDSU Associate Professor.

“Highly pathogenic avian influenza (HPAI) outbreaks have occurred throughout the U.S. this spring, affecting small backyard poultry flocks, as well as large commercial barns,” Daly said.

He explained that these outbreaks occurred along three different migratory bird flyways (Pacific, Central, and Mississippi). The South Dakota occurrence is the second to be identified in the Central flyway.    

“Influenza viruses are encountered every year by people and a variety of animals,” Daly said. “For the most part, these “flu” viruses stick to one species: human influenza viruses spread among people, avian influenza viruses (such as these particular HPAI viruses) spread among birds, and so on.  Occasionally, influenza viruses normally found in one species will infect other species. For example, certain swine influenza viruses have occasionally infected people, and certain avian influenza viruses, notably the H5N1 virus in Asia, occasionally infect people as well.”
 
Below, Daly responds to frequently asked questions in regards to the Highly pathogenic avian influenza (HPAI) virus.
 
Q:  What is happening with the affected farm? 
A:  State and federal animal health officials are responding to the outbreak according to long-standing protocols. Infected farms are placed under quarantine, meaning that no birds can leave or enter the farm. Remaining live birds are humanely euthanized and disposed of on the premise. The building and grounds are thoroughly cleaned and disinfected and sit idle for a period of time.
 
Q:  How will this outbreak affect neighboring farms? 
A:  State and federal response plans establish a 10 kilometer (approximately 6 miles) “control” zone, as well as a 20 kilometer “surveillance” zone around the infected farm. All poultry flocks in the control zone will be sampled by animal health officials and tested for avian influenza. All poultry flocks in the surveillance zone will be contacted by animal health officials to determine if any signs of illness or unexpected death losses have been noticed. 
 
Q:  What does this avian influenza virus do to these birds? 
A:  That this virus is termed “highly pathogenic” is no mistake. These strains affect birds so quickly that clinical signs are usually not noticed. The first signs noticed by flock owners are an unexpected number of dead birds. Weakness, difficulty breathing, and purple swelling of the comb and wattles are signs that may be observed prior to death. 
 
Q:  How do these domestic birds get infected by HPAI? 
A:  Birds infected with influenza discharge the virus through their droppings or nasal/respiratory fluids. Susceptible birds ingest or inhale the virus when they encounter those fluids. Most experts assume that the source of these HPAI viruses is migratory waterfowl traveling through the areas.  
 
It’s relatively easy to picture how a free-roaming backyard poultry flock could come in contact with migratory geese and ducks. However, modern poultry production features tight, environmentally controlled barns that typically exclude outside birds and limit human traffic as well. Wild birds congregating around air inlets, or people walking through areas that wild birds have frequented and then entering poultry barns are potential routes of transmission. Sampling of wild birds in the vicinity of outbreaks has not demonstrated a clear source or transmission route for these infections. 
 
Q:  How is this HPAI virus similar to other HPAI viruses found across the world? 
A:  Molecular analysis of the US HPAI H5N2 viruses shows that they are a combination of Asian HPAI viruses with low-pathogenic North American viruses. The HPAI type that has affected the South Dakota flock is an H5N2 type that carries the “H” antigen from highly-pathogenic Asian strains and the “N” from common low-pathogenic North American viruses. 
 
Q:  What bird species have been most commonly affected with HPAI H5N2? 
A:  Of domestic birds, turkeys have been most commonly affected by these outbreaks across the US, but chickens and a variety of backyard birds have also been identified. 
No wild bird infections have been detected yet in South Dakota, but in other states, the virus has most often been associated with ducks and geese. Birds of prey such as hawks, falcons, and eagles are also affected, presumably from eating infected waterfowl. While many sources mention pheasants as susceptible to HPAI, no pheasant death losses have been detected in South Dakota; however, a backyard pheasant flock in Washington State was identified as infected in January. 
 
Q:  What is the danger for people working with the affected birds? 
A:  There is no indication that these HPAI H5N2 avian strains affect people (or other animals). In each outbreak, agriculture officials work closely with state health departments to identify and monitor people who have been in close contact with infected birds. Typically, exposed people are offered preventative antiviral medications and are contacted each day for 10 days to ensure that they are not suffering flu-like symptoms. In other states, non-specific illnesses in some of these people have prompted further testing, but no influenza viruses have been found in any of these individuals to date.
 
Q:  Are there food safety problems associated with these HPAI outbreaks?
A:  No. Affected birds do not enter the food supply.  Furthermore, all influenza viruses are easily inactivated by proper cooking techniques. 
 
Q:  How can I protect my backyard flock from infection with these viruses? 
A:  Owners of backyard free-roaming birds should consider their proximity to places where waterfowl might congregate. If domestic birds can come into contact with waterfowl like ducks and geese, it might be prudent to confine the birds inside. Basic biosecurity protocols such as limiting visitors and vehicle traffic, and cleaning and disinfecting equipment used around other flocks, have increased in importance. 
 
Q:  How can I protect my commercial poultry flock? 
A:  Flock owners should pay close attention to barn security in terms of excluding wild birds and limiting human traffic into poultry barns. Anyone entering barns should adhere to strict policies regarding changing clothes and boots prior to entry. Vehicle and foot traffic should be closely controlled, as tires, boots or clothing that have had contact with wild bird areas are a potential route of entry for a HPAI virus into a barn. 
 
Q:  Who should I contact if I suspect HPAI? 
A:  If you notice unexplained death loss in your birds, contact your veterinarian or the South Dakota Animal Industry Board at 605.773.3321 as soon as possible. 
 
For more information, contact Dr. Daly, or the South Dakota Animal Industry Board at 605.773.3321. 

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