Newcastle disease (ND) is a viral disease of wild and domestic birds. There are many different strains of the ND virus that cause different degrees of disease in different bird species. A Scottish poem from 1897 is likely the first record of ND in wild birds. The poem refers to deaths in domestic chickens, great cormorants, and European shags.
Newcastle disease virus has caused major mortality events in wild double-crested cormorants in North America. The virus is also considered one of the most economically significant diseases of domestic poultry. The most recent outbreak of ND in poultry in the western United States occurred in 2003, resulting in the death or culling of over 4 million birds.
ND has been reported in over 240 species of birds, though the virus can likely infect all bird species. Outbreaks in double-crested cormorants and rock doves (pigeons) have caused extensive mortality amongst the two wild species. During one outbreak of ND in double-crested cormorants, other birds such as white-pelicans, ring-billed gulls, and California gulls also suffered. ND virus has been known to cause high mortality in domestic poultry and wild birds have been known to be the source of infection for domestic birds. ND virus can cause minor disease in humans, but is not considered a significant public health concern.
Newcastle disease virus is found worldwide. Outbreaks in double-crested cormorants usually occur in breeding colonies in March-September. In 1990, an outbreak of ND in double-crested cormorants in Canada resulted in the death of more than 10,000 birds. In the United States, outbreaks have been reported in wild cormorants at the Great Salt Lake, southern California, the Great Lakes region, and the Columbia River between Washington and Oregon. A domestic poultry flock in the Midwestern United States became infected with ND during an outbreak in cormorants in 1992. In 1997 an outbreak at the Salton Sea in California resulted in the death of about 2,000 cormorants. Outbreaks have been reported as recently as 2010 in double-crested cormorants in Minnesota, North Dakota, and Wisconsin.
Newcastle disease virus is highly contagious and is easily transmitted among susceptible birds. The virus is shed in the feces, body fluids, exhaled air, and eggs of infected birds, and it can be present in all body tissues. Birds become infected by inhaling virus particles or consuming contaminated food or water. The virus can survive for long periods of time outside of the host, so it can be transmitted by contact with contaminated inanimate objects. Humans can spread the virus to new locations by way of contaminated clothing, boots, and equipment.
Rock pigeons and double-crested cormorants infected with ND most often show neurological signs. This may include a loss of coordination, twisting of the head and neck, poor balance, tremors, and wing and/or leg paralysis. Newcastle disease should be suspected when several birds are observed with one-sided wing paralysis. One-sided wing paralysis is often characterized by thrashing on the water. Birds are still able to dive, but cannot fly. Cormorants that survive this disease often suffer from permanent wing or leg paralysis. Birds with this virus also often have bloody diarrhea. In cormorants, only the juveniles show clinical illness and mortality is usually limited to the young. Most ND infections in other wild bird species are asymptomatic.
Newcastle disease is diagnosed by laboratory identification of the virus.
There is no treatment for Newcastle disease.
Vaccines are used to prevent Newcastle disease outbreaks in domestic poultry and may be used in rare or endangered wild species. However, vaccination is not a practical option for free-ranging wild populations. ND virus can be transmitted between domestic and wild birds, so contact between domestic and wild birds should be prevented. Biosecurity is very important to prevent the spread of this virus between poultry farms and into the wild from infected premises. In the case of an outbreak, wildlife managers and poultry farmers must work together to minimize the impact of the disease on domestic and wild birds. Bird handlers should be stringent about decontaminating clothes, tools, and equipment to prevent the spreading of the disease.