Avian flu strain behind recent outbreaks related but not identical to 2014-15 strain
The US poultry industry is on high alert following reports of highly pathogenic avian influenza (HPAI) infecting wild birds and commercial flocks in poultry-dense regions of the US broiler market.
The USDA-ARS National Poultry Research Center in Athens, Georgia, has been involved in investigating the outbreaks. Laboratory director David Swayne, DVM, PhD, talked with Poultry Health Today about the new HPAI outbreaks and how the virus compares to 2014-15.
Q: What have you learned about the recent outbreaks of highly pathogenic avian influenza (HPAI)?
DS: We learned very early in this outbreak, which has just begun, that the threat of this virus continues for poultry across all farm species. Infections have been identified in a variety of wild ducks, chickens and turkeys, which indicates the virus can infect any of our farm poultry species.
Interestingly, the outbreak in a broiler flock is really new for 2022 compared to the 2015 outbreak. However, it is unknown why this occurred — whether a gap in biosecurity allowed the virus to get onto a single farm or if there’s a change in the virus biology that increases susceptibility to meat-type chicken. Our lab is doing research to answer these types of questions.
Q: Is this strain any different from the outbreaks in 2015?
DS: We do genetic analyses, and we can say these strains and the strains from 2014-15 are related. They are cousins and not identical. They have a common pedigree that goes back before 2013 when they split off.
Q: How is this virus spreading from wild birds to commercial operations?
DS: Infection with this virus in poultry results in the virus growing and being excreted from the mouth and its presence in the feces.
Generally, it’s spread by direct or indirect contact with wild waterfowl or other aquatic birds. Exposure to domestic poultry can be by eating the virus from a contaminant or even inhaled. Direct contact would require poultry to be exposed outdoors to infected wild birds.
We recommend that, at this time, outdoor poultry be brought indoors to protect them from exposure to infected wild birds.
The other way the virus can be brought into the house is tracking it in on shoes, clothes and equipment. So biosecurity becomes a very important part of the process to keep the virus out of the house.
Q: What is the likelihood more commercial operations will experience an outbreak with this HPAI?
DS: This is unknown. The outcome is highly dependent upon practicing the highest level of biosecurity to keep the virus out of houses and, of course, to bring poultry indoors to avoid any contact with infected wild aquatic birds.
Q: What is the best solution for control of HPAI?
DS: There is no cure for poultry once infected with HPAI. Prevention is by far the best strategy. While biosecurity practices may seem inconvenient, they are essential to keep the virus out of poultry flocks.
Q: What are the most important biosecurity practices to follow?
DS: Best biosecurity practices start with a clear line of separation at the entrance of the poultry house where a grower must change into work clothes and either disinfect or change boots.
Equipment should not be shared between farms. If you must share equipment, require a thorough disinfection before the equipment enters and leaves the house or farm.
Keep visitors out, except if a service person is needed to collect samples for testing. They should practice high biosecurity if they enter the farm.
Report any clinical signs the flock is off to your company veterinarian or service personnel. Drops in water or feed consumption, an increase in daily mortality should all be investigated to make sure you don’t have HPAI.
Q: As a refresher, what are the first signs of this disease and its progress through a flock?
DS: Virus infection starts by the birds reducing their water consumption, which is quickly followed by a decline in birds eating feed. And since the birds are sick, it will be quiet when you walk into the house because the birds are not moving around and vocalizing. But these signs are not specific for HPAI and can be caused by a variety of diseases.
A grower needs to bring these symptoms to the attention of the poultry veterinarian so he or she can take proper samples and send them to a diagnostic lab to make sure it’s not HPAI.
If it is HPAI, some of the birds may show signs of a respiratory illness or may have diarrhea. More likely, you will find scattered across the flock birds that die suddenly without showing any signs of illness. A few birds may show nervous signs or have blue or black discoloration of the comb or wattle, meaning those tissues are dying.
Generally, you will see an increase in mortality across the whole flock. If you leave it unchecked, as in no attention, mortality will approach close to 100%.
Posted on June 2, 2022