Thursday, February 29, 2024

Depopulation, biosecurity needed against AI

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By Barbara Olejnik

Poultry Times staff

ATLANTA — The need for rapid depopulation of infected birds and intense biosecurity on farms were major “Lessons Learned” from the 2015 outbreak of Highly Pathogenic Avian Influenza in the U.S.

These decisions were examined during the HPAI Lessons Learned program sponsored by U.S. Poultry & Egg Association and United Egg Producers held during the recent International Production & Processing Expo.

The HPAI outbreak, which lasted from December 2014 through the first part of June 2015, affected 211 commercial and 21 backyard poultry premises.

That outbreak resulted in the depopulation of 7.5 million turkeys and 42.1 million chickens.

However, Dr. Ben Wilman, Ag Forte director of global technical services in Willmar, Minn., pointed out that the time span for depopulation has been too long.

The time from when a sample is taken and diagnosed with AI to depopulation can run from five to 10 days.

“That is way too long,” Wilman said.

He noted that a barn on his company took six days to depopulate, and that at one time there were 30 barns in the process of being depopulated.

Wilman said foaming, one method of depopulation, is not 100 percent  effective, since live birds could be left.

“You need a Plan A, Plan B and Place C” for depopulations with people trained to accomplish the job, he said.

Wilman said the AI outbreak stopped “because we ran out of birds to kill.”

He added that it is believed that waterfowl introduced the virus to commercial flock, “but we kept it going” through crews and trucks bringing the virus from farm to farm.

The need to depopulate also results in increased personnel on infected farms.

Dr. Jill Nezworski of the Blue House Veterinary in Buffalo Lake, Minn., was active in working to halt the spread of the avian influenza outbreak.

“Depopulation leads to dozens more people on farms,” Nezworski said, noting that it is “hard to clear everyone perfectly every time” they visit a farm.

She noted that outside depopulation contractors cross the clean/dirty boundary line around a farm to get lunch, etc., and can carry the virus on clothes or even  dirt under fingernails.

Nezworski also pointed out that there has not been enough surveillance with most detection of the virus coming through increased mortality.

There is a need to “educate people on what to look for” and there also needs to be a “clear chain of command” about who to inform if an outbreak is suspected, Nezworski said, adding that “it’s okay to be overcautious.”

Dr. Lindsey Garber with USDA’s Animal & Plant Health Inspection Service Veterinary Services added that biosecurity on farms “could use some improvement.”

In studying how the virus got on farms, Garber pointed out that it is important to know where shared vehicles and equipment are used, as these could have transported the virus between farms.

However, she added that the effect of wind “couldn’t be ruled in or out” as the virus was detected in the air some distance away from an infected farm.

Other points studied as possible means of increasing the spread of the disease included the amount of corn grown in an area, bodies of water in surroundings, close proximity of highways and rendering trucks.

The U.S. has seen 39 outbreaks of avian influenza since 1959, although the 2015 outbreak has been the largest, said Dr. David Swayne, director, USDA Agricultural Research Service Southeast Poultry Research Laboratory.

Worldwide the virus has affected 500 million birds since 1996. Between 2002 and 2010, 14 countries have vaccinated poultry against HPAI, Swayne noted.

USDA has called for development of avian influenza vaccines as a precautionary measure but to date has not sanctioned the use of a vaccine.

Swayne said vaccines increase resistance to AI infection, prevent illness and death in poultry, reduce environmental contamination, reduce transmission to birds and maintain a farmer’s livelihood.

But, “vaccination is a stop gap, it doesn’t eradicate,” Swayne stressed.

What is needed for a vaccine program, he said, are:

  • High quality, high potency vaccines
  • A vaccine close to the HPAI strain
  • A proper program targeted to a specific sector or area
  • Adequate number of vaccines — at least two to get  minimum protection with a booster possibly needed
  • Monitoring of vaccinated population
  • Survey of vaccinated population to find any new infections or emergence of different strains.

Swayne noted that the most successful vaccine program has been in Hong Kong, which began vaccinations in 2002 and has seen only one outbreak since that time.

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