Survival of avirulent thermostable Newcastle disease virus (strain I-2) in raw, baked, oiled, and cooked white rice at ambient temperatures

Raw white rice has not been considered a good carrier for oral vaccination, probably because of its antiviral activity. Methods are required to overcome antiviral activity in raw white rice. This study was carried out to determine the effects of various treatments of raw white rice on the survival of strain I-2 of Newcastle disease virus. These included cooking and baking the rice or mixing the rice with vegetable oil prior to coating with vaccine virus. The vaccine-coated rice was then stored for 30 min and 24 h, followed by quantitative recovery of the virus. Thirty min after mixing, uncooked, cooked, and baked rice, and rice mixed with vegetable oil showed titers of 10(6.2), 10(7.2), 10(6.6), and 10(7.0) EID(50)/0.1 ml, respectively. After storage for 24 h at 22-25℃, the titers dropped to 10(5.0), 10(6.5), 10(5.0), and 10(6.0) EID(50)/0.1 ml for uncooked, cooked, baked, and oiled rice, respectively.