Sunday, January 17, 2016

Indiana BOAH: Additional H7N8 Outbreaks Were LPAI

Indiana BOAH - Jan 17th


An update today from Indiana's Board of Animal Health clarifies and revises last night's statement now that laboratory testing has come back on 8 of the 9 newly discovered outbreaks.

Instead of all of those outbreaks being HPAI H7N8, the vast majority (so far) are LPAI.

Highly pathogenic avian influenza is more apt to be recognized based on the appearance and behavior of infected birds, and that is what led to the initial quarantine and  testing.  LPAI infection is more subtle, and isn't always readily apparent without testing.

It turns out that eight of the nine subsequent positive tests returned from other farms in Dubois county are LPAI H7N8, with one still pending.  No additional farms have been announced as infected today.

This statement was emailed a short while ago from the Indiana BOAH.

Indiana Clarifies Avian Flu 

Findings in Nine Flocks

Laboratory Results Confirmed Overnight


INDIANAPOLIS (17 Jan. 2016)--Laboratory testing of samples from eight of nine Southern Indiana turkey flocks was completed overnight by the U.S. Department of Agriculture (USDA) National Veterinary Services Laboratory in Ames, Iowa. While all nine were announced as H7 influenza-positive yesterday, the specific strain was yet to be determined. The Indiana State Board of Animal Health (BOAH) has been informed eight are low-pathogenic H7N8. Testing continues on the remaining sample.

Avian influenza does not present a food safety risk; poultry and eggs are safe to eat. The Centers for Disease Control and Prevention (CDC) considers the risk of illness to humans to be very low.

Indiana State Veterinarian Bret D. Marsh, DVM calls this good news, and evidence that Indiana’s aggressive surveillance and response efforts in Dubois County are working.
“The low-path H7N8 virus was identified during testing in the 10-km zone around the initial flu-positive flock,” Dr. Marsh said. “Because flu viruses are constantly mutating, we want to catch any case as early as possible after infection. We know this virus strain can intensify, so finding these cases as low-path strains shows we are keeping pace with the spread of this disease in the area.”

In addition to the HxNx naming scheme for specific strains, AI viruses are further classified by their pathogenicity—the ability of a particular virus strain to produce disease in domestic chickens. Highly pathogenic avian influenza (HPAI) virus strains are extremely infectious, often fatal to domestic poultry, and can spread rapidly from flock to flock. Low pathogenicity avian influenza (LPAI) virus strains occur naturally in wild migratory waterfowl and shorebirds without causing illness. LPAI viruses have the potential to mutate into HPAI.

“This finding does not alter the aggressive control strategy BOAH has set forth,” added Dr. Marsh. “Nor does it change our resolve to eliminate this virus wherever we find it.”

Priority response by the state of Indiana and USDA continues on all the infected farms. Turkeys are being humanely euthanized on infected sites within 24 hours of diagnosis. Depopulation eliminates the source of infection to prevent the disease from spreading. Disposal of the turkeys, primarily via indoor composting, will be followed by thorough cleaning and disinfection of all barns.

Aggressive testing of other poultry farms in the area continues. During the last 24 hours, commercial farms have yielded 100 negative flu tests, beyond the nine new positives. In addition, state and federal teams have visited 503 residences in the area to identify any small flocks for testing. Tests are pending on 17 small flocks. Residential visits will continue in the 10-km area.

 From APHIS, a similar announcement (excerpt below), the a brief discussion.

Update on H7 Avian Influenza Cases in Indiana, Additional Flocks Now Confirmed as Low Pathogenic

Cases Found Through Surveillance Testing in Initial Control Area
WASHINGTON, January 17, 2016 -- The United States Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) has confirmed the pathogenicity of eight of the nine H7N8 avian influenza detections announced on January 16. The turkey flocks have been confirmed as low pathogenic avian influenza, with additional testing ongoing for the ninth flock.

These January 16 detections were identified as part of surveillance testing in the control area surrounding the initial highly pathogenic H7N8 avian influenza (HPAI) case in that state, identified on January 15.

The pathogenicity of a virus refers to its ability to produce disease.  Birds with low pathogenic avian influenza (LPAI) often show no signs of infection or only have minor symptoms.  HPAI viruses spread quickly and cause high mortality in domestic poultry.  H7 LPAI viruses have been known to mutate into HPAI viruses in the past.

“It appears that there was a low pathogenic virus circulating in the poultry population in this area, and that virus likely mutated into a highly pathogenic virus in one flock,” said Dr. John Clifford, USDA Chief Veterinarian. “Through cooperative industry, state and federal efforts, we were able to quickly identify and isolate the highly pathogenic case, and depopulate that flock.  Together, we are also working to stop further spread of the LPAI virus, and will continue aggressive testing on additional premises within the expanded control area to ensure any additional cases of either HPAI or LPAI are identified and controlled quickly.”

(Continue . . .)
HPAI viruses have been generated in the lab by repeated passage of LPAI viruses through chickens (cite FAO) but exactly how and why this occurs naturally is poorly understood (see JVI  Emergence of a Highly Pathogenic Avian Influenza Virus from a Low Pathogenic Progenitor). .

While we haven't seen it happen all that often, the risk is considered great enough that all LPAI H5 and H7 outbreaks must be reported to the OIE, and immediate steps must be taken to contain and eradicate the virus. 

Over the past year we've seen an unusual increase in number of these LP to HP conversions  (see You Say You Want An Evolution?) involving multiple H7 & H5 subtypes.  Now, it appears, we can add Indiana to the list.

It is going to be very interesting to see what the epidemiological investigation turns up on this newest avian influenza virus, and we will hopefully learn more about the European outbreaks in the days ahead as well.

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