The U.S. Department of Agriculure’s partially shut down Animal and Plant Inspection Service (APHIS) is being challenged by the deadly and highly contagious Virulent Newcastle disease that’s jumped from backyard poultry to commercial flocks in California.

USDA officials are quick to say that Virulent Newcastle is not a food safety risk. Humans are not exposed to Virulent Newcastle from eating poultry products that are properly cooked. People working with sick birds can become infected, but it’s rare.

Since last May, California has experienced Virulent Newcastle infections of birds from backyard flocks. APHIS and the California Department of Food and Agriculture have been working since then to locate, limit and eradicate the disease.

Eradication has resulted in 60,000 birds being killed. Until recently, the bird kill was centered on those backyard flocks.

That changed on Dec. 16, 2018, when APHIS reported Virulent Newcastle disease was present in a commercial flock of 110,000 6-week-old layer chickens in Riverside County, CA. Such reports to the World Organization of Animal Health (OIE) are mandatory.

On Jan. 8, APHIS reported Virulent Newcastle disease in a second large commercial layer flock in south California. And a third infected commercial flock was reported two days later.

All three are part of the southern California outbreak that began in spring 2018 with backyard exhibition birds centered in Riverside County.

The symptoms that humans working with birds might develop are usually mild and limited to conjunctivitis and/or flu-like reactions. Human infections can be prevented by using standard personal protective equipment.

APHIS said federal and state partners are conducting additional surveillance and testing in southern California. Nearby commercial farms are being checked and encouraged to step-up biosecurity measures to prevent additional spread of the disease.

“It is essential that all bird owners follow good biosecurity practices to help protect their birds from infectious disease,” APHIS said in a statement confirming the infections in the third commercial flocks. “These include simple steps like washing hands and scrubbing boots before and after entering a poultry area; and cleaning and disinfecting tires and equipment before moving them off the property.”

For the birds, mostly chickens, Virulent Newcastle is highly contagious and a fatal viral disease that strikes the respiratory, nervous and digestive systems. Death often comes before clinical signs are noticable. An unvaccinated flock will experience a 100 percent fatality rate.

In addition to sudden death, clinical signs include sneezing, gasping for air, nasal discharge, coughing, greenish watery diarrhea, decreased activity, tremors, drooping wings, twisting of the heat and neck, complete stiffness and swelling of eyes and neck.

Steve Lyle, the spokesman for the California Department of Agriculture, said themassive bird kill was necessary. “No one wants their birds euthanized,” he said. “In fact, we don’t like the idea of euthanizing birds at all, but we know scientifically that this is the only option that will stop the spread of the virus and eradicate the disease.”

Lyle said most Californians “understand what we’re up against when we share specific information with them, particularly if they have seen what this virus does to poultry. It is a highly contagious killer of poultry.”

The APHIS work to eradicate the disease has continued since Dec. 22, 2018, the date of the partial shutdown of the federal government that includes USDA agencies.