Exotic Newcastle disease (END) is a contagious and fatal disease affecting all species of birds. Previously known as velogenic viscerotropic Newcastle disease (VVND), END is one of the most infectious diseases of poultry worldwide. A death rate of nearly 100 percent can occur in unvaccinated poultry flocks. The virus is so virulent that many birds die prior to showing clinical signs, and END infection can have high mortality even in vaccinated birds (University of Georgia, 2003).
END is classified as a foreign animal disease in the United States, historically causing severe economic losses when commercial poultry industries become infected, as occurred in a major outbreak of END in southern California in 1971. The disease threatened not only California poultry production, but it also had a significant economic impact on the entire U.S. poultry and egg industry. In all, 1,341 infected flocks were identified and 11.9 million birds were destroyed over a multiyear disease control effort. Disease eradication cost taxpayers $56 million (over $250 million in 2003 dollars), severely disrupted the operations of many producers, and increased the price of poultry and poultry products to U.S. consumers (Utterback, 1973; Davidson-York et al., 1998). It took 3 years to fully eradicate the disease, and nearly two decades before another outbreak of END occurred in U.S. commercial poultry. In the early 1990s, over 26,000 commercial turkeys were destroyed in North Dakota following detection of END. The virus is believed to have been transmitted to the turkeys from cormorants or other free-ranging birds. Hundreds of cormorants had previously died at a lake not far from the turkeys, in an outbreak that is believed to be the first documented Newcastle-related die-off of wild birds in the United States (Meteyer et al., 1997). Though END virus has not been detected in commercial birds in the United States since then, it is now known to exist in free-ranging wild birds, as well as in psitticine species. A variety of psitticine species enter the United States through the pet bird trade, generally traveling through USDA quarantine stations; however, illegal movements across U.S. borders also occur. END is detected nearly every year in California, primarily in psitticine and free-flying wild-bird species; however, in 1998, END was detected in urban gaming chickens in the state (Crespo et al., 1999). Subsequent to the 1971 outbreak, the presence of END has been detected numerous times through case submissions to the state’s diagnostic laboratory (passive surveillance), confirmed as END by the federal laboratory system, and rapidly