Avian Influenza- One Year Later, What have We Learned?

It’s been a little over one year since the first case of HPAI (Highly Pathogenic Avian Influenza) H5N2 was confirmed in Minnesota.  This infectious strain of avian influenza popped up in a commercial turkey flock in Pope Country in central Minnesota last March.  The last two cases of HPAI H5N2 were reported on June 5th, nearly three months to the day afterwards.  These twelve weeks of infection took Minnesota’s economy through the wringer, causing an estimated $647.2M hit to poultry production and $171.7M in lost wages, salaries, and benefits according to a University of Minnesota Extension study. 

Since this time, the smoke has cleared and settled.  But has Minnesota fully recovered and are we better prepared if this pathogenic AI strain returns to the region?

Avian influenza (AI), or the bird flu, is caused by infection of birds with AI type A viruses.  Wild birds harboring type A virus can serve as pathogen reservoirs, shedding the virus in saliva, nasal secretions, and feces.  At risk birds become infected after exposure to shed virus or by contacting surfaces contaminated with virus.

AI type A viruses exist in two flavors: low pathogenic AI (LPAI) and highly pathogenic AI (HPAI).  This classification depends on the virus’s ability to cause disease and mortality, although both LPAI and HPAI infections can spread rapidly among birds.

Infection with LPAI typically results in no observable disease or very mild symptoms, such as ruffled feathers or a slight drop in egg production.  LPAI might even go undetected in domestic birds. 

HPAI infection, on the other hand, is highly pathogenic and causes severe disease with high mortality rates.  Infection with these viruses typically results in sudden death, lack of energy and appetite, decrease in egg production, swelling, coughing, and sneezing.  HPAI can quickly diffuse through and decimate a domestic flock of birds.

Wild birds can naturally carry native strains of AI.  These viruses are usually of the low pathogenic, LP, variety, but still can spread to domesticated birds.  Birds infected with LPAI typically show no symptoms.  However, LPAI H5 and H7 strains can mutate into HPAI, then becoming a large problem.

In December 2014, the USDA detected HPAI H5N2, H5N8, and H5N1 strains in domestic and wild birds in the United States, including in the Mississippi flyway- an avian migratory path that follows the Mississippi River from the Gulf of Mexico to breeding grounds at the river headwaters in Canada. 

Infected birds were ultimately detected in a widespread path across the US, including: Arkansas, California, Iowa, Idaho, Kansas, Minnesota, Missouri, Montana, North Dakota, Nevada, Oregon, Utah, South Dakota, Washington, Wisconsin, and Wyoming.

AI type A viruses rarely infect people, and pose little to no threat to human health.  Proper handling and cooking of infected eggs and meat to an internal temperature of 165F will even kill off the virus and make the food safe to eat, according to the USDA.

The real threat of these HPAI strains was more bird-on-bird directed, particularly toward domesticated poultry.

HPA1 H5N2 blasted Minnesota’s turkey production economy, especially in the central and southwestern parts of the state.  Nine million birds were affected- including five million turkeys and four million egg laying hens- according to the Minnesota Board of Animal Health, impacting at least 110 separate sites.  The trickle-down down effects were felt for months, impacting industries even indirectly connected to turkey production.

Once a Minnesota turkey production site tested positive for HPAI H5N2, it was out of service for months.  If HPA1 was detected in one bird in a barn, the whole flock in that space was depopulated and destroyed to prevent further viral spread.  Poultry carcasses went through an unpleasant composting process inside affected barns for at least twenty-eight days to destroy any virus present in the birds.  The area was disinfected and scoured for at least twenty-one days.  Infected farms had to be completely eradicated of virus before being repopulated and resupplied with new poultry. 

Even the restocking of farms was not a straight forward process.  Egg and poult- or baby turkey- production was down at several frequently used poultry suppliers in Minnesota and Wisconsin, delaying production ramp-up at cleansed farms.

Layoffs and cut hours weighed down Minnesota’s turkey industry for the spring and summer.  Trickle-down effects also reared their head in seemingly unattached markets like truck transportation, restaurants, hospitals, and general merchandise stores, according to a University of Minnesota Extension report. 

All 110 HPAI infected Minnesota farms were disinfected and re-stocked by December 2015.  Farmers apprehensively waited for a possible return of HPAI H2N5 with the fall wild bird migration, but Minnesota’s turkey passed through that point unharmed.

One year after the first outbreaks occurred in the state, have we learned any information to better prepare Minnesota’s economy against another round of infection?

Researchers are still no closer to addressing how HPAI H5N2 reached Minnesota’s domestic birds in the first place.  Many conflicting theories continue to circulate.

The virus was originally thought to have spread from wild, migrating birds, especially ducks and geese.  The MN Department of Natural Resources (DNR) churned into full gear last year and collected over 6200 samples from wild birds, detecting only two cases of HPAI.

That’s a lot of poop for very little information.

The MN DNR has since scaled down their sampling efforts, a point of contention with some of the state’s turkey producers.

Poor biosecurity practices may have helped the virus to spread between farms.  According to one theory, actively tilled fields near poultry barns may have generated air borne virus from infected wild bird droppings, which then infected domestic poultry.  If migratory birds were the viral reservoirs in the first place.

Another idea is that a low-pathogenic virus may have incubated, undetected, in layer hens, and at some point mutated into pathogenic HPAI H5N2.

A vaccine protecting domestic birds against several AI H5 strains, including H5N2, is still being developed.

Join us at the Worthington Bio Science Conference Thursday April 7th for a dinner panel discussion around avian flu, including innovative research, management practices, and market impact of the outbreak in Minnesota. 

Local experts Jeff Barber, of TM Farms, Dr. Jill Nezworski, of Blue Horse Veterinary, and Dr. Carol Cardona, Professor in the UMN College of Veterinary Medicine, will lead the discussion.