Infectious avian virus threatens California's $3 billion poultry industry
At press time in January, an outbreak of exotic Newcastle disease in California that began in privately owned backyard flocks had reached five commercial poultry operations housing an estimated 1.2 million birds.
As a result, Gov. Gray Davis declared a state of emergency, while the Department of Agriculture announced an "extraordinary emergency" to protect California's $3 billion poultry industry from the highly infectious avian disease. The USDA and California Department of Food and Agriculture had restricted shipment of all species of birds and poultry products in several southern California counties.
A task force of more than 600 federal and state employees was marshaled to identify infected flocks, euthanatize and dispose of birds, clean and disinfect sites, and provide educational material about exotic Newcastle disease to the state's poultry industry and area residents.
The avian disease was confirmed in California last October in privately owned backyard flocks (see JAVMA, Nov. 15, 2002, page 1369). Two months later, the virus had spread to four commercial farms in Riverside, San Bernardino, and San Diego counties.
In January, the disease was also confirmed in a backyard flock in Nevada.
California health officials were investigating whether the disease had caused conjunctivitis in two workers involved in the eradication effort.
"To the poultry industry, exotic Newcastle disease is as (devastating as) foot-and-mouth disease would be to the livestock industry," Dr. Ron DeHaven, deputy administrator of the USDA Animal and Plant Health Inspection Service Veterinary Services, said at a meeting of AVMA leaders in Chicago this January.
The last outbreak of exotic Newcastle disease in California's commercial poultry flocks was 1971, resulting in the loss of 12 million birds at a cost of $56 million. In this latest outbreak, approximately 734,138 birds had been depopulated as of late January.
The Office International des Epizooties in Paris, which monitors animal diseases worldwide, categorizes exotic Newcastle disease as a list A disease, meaning the virus is highly transmissible and a serious threat to international animal trade.
The trade implications of the disease outbreak in California are "huge," according to Dr. DeHaven. The United States exports about 25 percent of its poultry products, he said. Canada has banned all poultry meat and poultry meat products from California, along with hatching eggs and live poultry. Many other countries have implemented trade restrictions.
Birds infected with exotic Newcastle disease often die without showing any clinical signs. All bird species are susceptible to the virus, which attacks the respiratory, nervous, and digestive systems. It is passed through direct contact between healthy birds and the bodily discharges of infected birds.
High concentrations of exotic Newcastle virus are in birds' discharges and can be spread easily on shoes and clothing, and by other means. The virus can be spread by vaccination and beak trimming crews, manure haulers, and poultry farm employees. It can also survive for several weeks in a warm, humid environment on birds' feathers, manure, and other materials.