Viruses Genomes - NEWCASTLE DISEASE VIRUS

Newcastle disease viruses (NDV's) occur as three pathotypes: lentogenic, mesogenic, and velogenic, reflecting increasing levels of virulence. Velogenic Newcastle disease (VND) is the most severe form of Newcastle disease and is probably the most serious disease of poultry throughout the world. Newcastle disease was first reported in 1926 in the East Indies and then in 1927 at Newcastle-on-Tyne, England, after which it is named. Chickens are highly susceptible, while ducks and geese can be infected and show few or no clinical signs to the same strain.

NDV is spread primarily through direct contact between healthy birds and the bodily discharges of infected birds. The disease is transmitted through infected birds' droppings and secretions from the nose, mouth, and eyes. NDV spreads rapidly among birds kept in confinement, such as commercially raised chickens. High concentrations of the NDV are found in birds' bodily discharges; therefore, the disease can be spread easily by mechanical means. Virus-bearing material can be picked up on shoes and clothing and carried from an infected flock to a healthy one. NDV can survive for several weeks in a warm and humid environment on birds' feathers, manure, and other materials. It can survive indefinitely in frozen material.

NDV affects the respiratory, nervous, and digestive systems. Symptoms are very variable depending on the strain of virus, species of bird, concurrent disease and preexisting immunity. The incubation period for the disease ranges from 2 to 15 days. An infected bird may exhibit the following signs:

Respiratory problems including sneezing, gasping for air, nasal discharge, coughing, greenish, watery diarrhea, nervousness, depression, muscular tremors, drooping wings, twisting of head and neck, circling, complete paralysis and swelling of the tissues around the eyes and in the neck. Sudden death NDV is so virulent that many birds die without showing any clinical signs.
To date there is no known treatment for Newcastle Disease.

NDV is currently being studied as a possible treatment for some cancers. NDV not only infects birds it also infects humans. Although NDV causes a potentially fatal, noncancerous (Newcastle) disease in birds, it causes only minor illness in humans. NDV appears to replicate substantially better in human cancer cells than it does in most normal human cells. Individual strains of NDV are classified as lytic or nonlytic. Viruses of both strain types can kill cancer cells, but lytic strains have the potential to do this more quickly because they damage the plasma membrane of infected cells. Nonlytic strains appear to kill by interfering with cell metabolism. Lytic strains of NDV have been studied in humans for their ability to kill cancer cells directly, but viruses of both strain types have been used to make vaccines in an attempt to stimulate the immune system to fight cancer. NDV-based anticancer therapy has been reported to be of benefit in some clinical studies, however much further research is still necessary.

References:

http://www.avianbiotech.com/Diseases/Newcastle.htm
http://www.vet.uga.edu/vpp/gray_book/FAD/vnd.htm
http://www.meb.uni-bonn.de/cancer.gov/CDR0000062978.html
http://ianrpubs.unl.edu/animaldisease/g1505.htm
http://www.aphis.usda.gov/lpa/issues/enc/vnd.html