Newcastle disease virus nucleic acid testing

Newcastle disease (ND) is a class of infectious diseases. It is an acute, febrile, septic, and highly contagious disease caused by the Newcastle disease virus in poultry. Characterized by high fever, difficulty breathing, dysentery, neurological disorders, and mucosal and serosal bleeding. With high incidence rate and mortality, it is a major infectious disease endangering poultry industry. OIE classifies it as a Class A epidemic. Newcastle disease virus is a type I avian paramyxovirus (APMV-1) belonging to the family Paramyxoviridae and the genus Avilavirus. The virus exists in all tissues, organs, body fluids, secretions, and excretions of diseased birds, with the highest toxicity in the brain, spleen, and lungs, and the longest toxicity in the bone marrow. Strong resistance under low temperature conditions, can survive for 12 years at 4 ℃, and can survive for more than 10 years at -20 ℃; Vacuum freeze-dried viruses can be stored for 30 days at 30 ℃ and 230 days at 15 ℃; There are significant differences in the stability of different strains to heat. The virus has weak resistance to disinfectants, sunlight, and high temperatures. Generally, the commonly used concentration of disinfectants can quickly kill it. Many factors can affect the effectiveness of disinfectants, such as the number of viruses, the type of virus strain, temperature, humidity, sunlight exposure, storage conditions, and the presence of organic matter. Especially, the presence of organic matter and low temperature have the greatest impact. Chicken, pheasant, turkey, guinea pig, and quail are susceptible. Among them, chickens are the most susceptible, followed by wild chickens. There are differences in susceptibility among chickens of different ages, with young and middle-aged chicks having the highest susceptibility, while older chickens over two years have lower susceptibility. Waterbirds such as ducks and geese can also be infected with this disease, and the virus has been isolated from ducks, geese, swans, gannets, and cormorants, but they generally cannot transmit the virus to poultry. Pigeons, turtledoves, crows, sparrows, starlings, eagles, swallows, and other freely flying or caged birds are mostly naturally infected with this disease or accompanied by clinical symptoms or hidden processes. In history, several countries have caused the epidemic of this disease due to the import of ornamental birds. Sick chickens are the main source of infection for this disease. Within 24 hours before the onset of clinical symptoms, the virus is excreted from the mouth, nose secretions, and feces of infected chickens. The virus exists in all tissues, organs, body fluids, secretions, and excreta of diseased chickens. During the intermission of the epidemic, infected chickens are also a source of infection for this disease. Birds are also important spreaders. The virus can invade the body through the digestive tract, respiratory tract, eye conjunctiva, injured skin, and cloacal mucosa. This disease can occur throughout the year, but is more common in spring and autumn. Once the disease occurs in chickens on the farm, it can spread to the entire flock within 4-5 days