Outbreaks of virulent Newcastle disease (vND) that have spread from backyard to commercial flocks in California are providing a wake-up call to the entire US poultry industry about the need for ND monitoring and adherence to strict biosecurity, Joseph Giambrone, PhD, a professor at Auburn University, told Poultry Health Today.
As of this writing, USDA has confirmed more than 400 cases of vND in California that include three commercial layer flocks. There has also been a case in Utah as well as one in Arizona; both involve small backyard flocks and are believed to be connected to the California outbreak.
“No question about it,” Giambrone said when asked if the US poultry industry should be concerned about these regional outbreaks.
Virulent ND is a highly contagious, deadly viral disease also called “exotic ND” or velogenic ND. The professor explained that it affects both the respiratory and enteric tracts. The source is virtually always backyard birds. It’s a difficult situation because it’s impossible to keep track of backyard birds and their numbers, he said, and noted that wild birds can also be a source of infection.
On commercial farms, poultry houses become an incubator for vND due to their large size, and the problem is amplified, he said.
Monitoring is essential
Giambrone stressed the importance of monitoring. “It’s similar to avian influenza in that you have to continually, continually monitor.” If anything out of the ordinary is found, such as increased mortality or a combination of respiratory and enteric disease, it needs to be reported to the state veterinarian. The farm may need to be quarantined.
Commercial farms need to remain vigilant about biosecurity and make sure anyone who comes onto the farm has no contact with backyard birds. Care must be taken to avoid exposing flocks to vND due to sharing of contaminated equipment, which is one of the ways avian influenza is spread, he said.
At least in the southeastern US, where most of the poultry industry is concentrated, live-bird markets aren’t permitted as they are in California, Giambrone added, which helps reduce the spread of vND.
The role of vaccination, he continued, takes on added importance in light of the California vND outbreaks, but it can be difficult, particularly for layer producers with birds in cages and automated water systems. It’s hard to get all the birds to drink the water, and live ND vaccines can be reactive and affect egg production and shell quality.
“So, commercial producers are reluctant to continue to vaccinate,” he explained. In addition, it costs money to vaccinate, and both live and killed ND vaccines are only effective for a certain amount of time, Giambrone said.
Nevertheless, he thinks vaccination is good insurance. The question is how much protection each farm needs. “How much insurance are you willing to pay for?” Giambrone asked.
“With Newcastle, at least we have the vaccines to prevent the spread.” For commercial layer farms anywhere near farms with an outbreak, “it would be incumbent on you to do serological testing…then re-vaccinate, even if it’s going to cost you in production,” Giambrone said.