High Path Avian Influenza has been in the news lately as outbreaks have occurred both in the United States and abroad.
Avian Influenza Update
Mohamed El-Gazzar, DVM, MAM, PhD, DACPV
The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) announced on March 5, 2017 the detection of H7 Highly Pathogenic Avian Influenza (HPAI) in the state of Tennessee. The affected flock is a Broiler Breeder, 30 to 45 weeks of age, located on an 8 house farm (~10,000 birds in each house) in Lincoln County, located in South Central Tennessee, 2 miles from Alabama border. On Thursday March 2nd, mortality increased to 132 dead in one house. On Friday March 4th, mortality jumped up to 500. Positive samples from only one house out of 8 were determined to be H7 by Tennessee NAHLN and confirmed by National Veterinary Services Laboratories (NVSL) late Saturday. By Sunday March 6th afternoon, all houses had been depopulated and onsite burial operations were underway. A control zone of 10 miles (not 10 Kilometers) was immediately started and the initial surveillance of commercial and noncommercial poultry premises within this zone (which extends into the state of Alabama) is near completion. No further positive samples within the zone have been detected thus far.
On March 7th, USDA’s NVSL confirmed that the complete subtype of the Tennessee virus is H7N9 based on the full genome sequence of all 8 influenza genomic segments. They also emphasized that based on the sequence the virus is of North American (NA) lineage and “is NOT the same as the China H7N9 virus that has impacted poultry and infected humans in Asia”. As NVSL explains, while the Tennessee and China viruses have the same designated subtype, they belong to genetically distinct lineages. What is referred to as the North American lineage is the genetic lineage that can be found in migratory wild birds of North America. Wild birds are suspected to be the source of this outbreak as well. While there is no identified direct link between wild birds and this particular farm in Tennessee so far, the H7 NA lineage was detected in wild birds multiple times this year. We don’t know how this virus could have jumped from wild to domestic birds, but it is important to note that Low Pathogenic Avian Influenza (LPAI) can transform into HPAI after they circulate in domestic poultry.
On March 9th, the Tennessee State Veterinarian confirmed another H7N9 influenza case in a commercial chicken breeder flock in Giles County, Tennessee, which is the county immediately to the east of Lincoln County, where the initial H7N9 virus was detected. However, this case in Giles County is Low Pathogenic Influenza (LPAI). No mortality or clinical signs were reported and it was detected during a routing surveillance testing. On March 14th, Alabama announced investigation of 3 potential cases of H7 in Jackson, Lauderdale, and Madison counties in north Alabama, all low pathogenic, one in a commercial breeder and two in noncommercial flocks. Latter on March 16th a second case of H7 HPAI was confirmed in another broiler breeder flock just one mile away from the index case in Tennessee with high mortality. On March 18th a commercial breeder flock was confirmed to be H7 positive in Christian County, Kentucky with no clinical signs suggesting that it is low pathogenic. Then two more cases were confirmed in Pickens and Madison counties in Alabama on March 22nd. And finally on March 22nd a flock of commercial poultry in Cullman County has tested positive for H7 with no clinical signs.
All in all, we had two highly pathogenic H7 cases, both in Tennessee, 1 mile apart. Also, we had several low pathogenic H7 cases in commercial and noncommercial poultry in Tennessee, Alabama, and Kentucky, in addition to one detection of H7 in wild birds in Kentucky. These findings highly suggest that we have a low pathogenic virus given the chance to circulate in domestic poultry until it was transformed into a highly pathogenic virus. This is similar to the Indiana H7 HPAI outbreak of last year.
Meanwhile, another reportable influenza virus was detected in a commercial turkey flock in the state of Wisconsin. A 6-house farm containing 84,000 market turkey toms with 3 houses at 16 weeks of age and 3 houses at 6 weeks of age was confirmed to be positive for H5N2 North American Lineage virus, which is different from the 2015 virus. This virus was classified as LPAI, mild signs of depression prompted the testing of the flock. But because it’s an H5 virus, and has the capacity to transform into a HPAI, it is reportable to international organizations. This flock will not be depopulated, it will be sent to the processing plant through a controlled marketing process. The flock will be tested using PCR weekly to ensure the cessation of viral shedding before they are moved to the processing plant.
For the second year in a row, an influenza virus was able to jump from wild birds to a commercial poultry population and turn into HPAI. In our view, this points to a significant weakness in our influenza surveillance systems. Our inability to detect these viruses while they are circulating in domestic poultry, allowing them to blindside us and showing as HPAI outbreaks, invites a revision to our surveillance methodology. A review of “Testing Protocols for Disease Surveillance in Poultry” was written last year (http://vet.osu.edu/sites/vet.osu.edu/files/documents/extension/Vol%2042%20No%205.pdf) detailing the decision making process as it relates to improving surveillance methodology.
USDA Confirms Second Case of Highly Pathogenic Avian Influenza in a Commercial Flock in Lincoln County, Tennessee
USDA Animal and Plant Health Inspection Service sent this bulletin at 03/16/2017 11:15 AM EDT
The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed a second case of highly pathogenic H7N9 avian influenza in a commercial breeder flock in Lincoln County, Tennessee. This H7N9 strain is of North American wild bird lineage and is the same strain of avian influenza that was previously confirmed in Tennessee. It is NOT the same as the China H7N9 virus that has impacted poultry and infected humans in Asia. The flock of 55,000 chickens is located in the Mississippi flyway, within three kilometers of the first Tennessee case. CLICK HERE TO READ FULL ARTICLE
Expert: Bird flu outbreak nation’s worst since 2015
March 22, 2017 by Jay Reeves
A bird flu outbreak that has led officials to euthanize more than 200,000 animals in three Southern states already is the nation’s worst since 2015 and new cases are still popping up, an expert said Wednesday.
The disease was first confirmed in southern Tennessee earlier this month and has since been detected in northern Alabama and western Kentucky.
Read more at: https://phys.org/news/2017-03-expert-bird-flu-outbreak-nation.html#jCp