Lactose pellets--a new approach to oral vaccination of village chickens against Newcastle disease.

Newcastle disease in village chickens in developing countries can now be controlled with vaccines containing thermostable, avirulent V4 virus delivered on food. Logistical problems arise because 7 to 10 g of food vaccine must be allowed for each chicken. Lactose-based pellets have been prepared that contain an immunizing dose of V4 virus in a single pellet, even after long periods of storage. Protective levels of antibody were generated in chickens fed individual pellets, or in groups of chickens fed vaccine pellets mixed with normal food. Chickens receiving vaccine pellets developed a level of protection against challenge with virulent Newcastle disease virus similar to that achieved with vaccine added to food. This process when refined will allow the preparation of vaccine in regional laboratories and delivery without refrigeration to villages.