Experimental infection with Brazilian Newcastle disease virus strain in pigeons and chickens

Abstract This study was designed with the goal of adding as much information as possible about the role of pigeons (Columba livia) and chickens (Gallus gallus) in Newcastle disease virus epidemiology. These species were submitted to direct experimental infection with Newcastle disease virus to evaluate interspecies transmission and virus-host relationships. The results obtained in four experimental models were analyzed by hemagglutination inhibition and reverse transcriptase polymerase chain reaction for detection of virus shedding. These techniques revealed that both avian species, when previously immunized with a low pathogenic Newcastle disease virus strain (LaSota), developed high antibody titers that significantly reduced virus shedding after infection with a highly pathogenic Newcastle disease virus strain (São Joao do Meriti) and that, in chickens, prevent clinical signs. Infected pigeons shed the pathogenic strain, which was not detected in sentinel chickens or control birds. When the presence of Newcastle disease virus was analyzed in tissue samples by RT-PCR, in both species, the virus was most frequently found in the spleen. The vaccination regimen can prevent clinical disease in chickens and reduce viral shedding by chickens or pigeons. Biosecurity measures associated with vaccination programs are crucial to maintain a virulent Newcastle disease virus-free status in industrial poultry in Brazil.

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 carrierfor oral vaccination, probably because of its antiviralactivity. Methods are required to overcome antiviralactivity in raw white rice. This study was carried out todetermine the effects of various treatments of raw whiterice on the survival of strain I-2 of Newcastle diseasevirus. These included cooking and baking the rice ormixing the rice with vegetable oil prior to coating withvaccine virus. The vaccine-coated rice was then stored for30min and 24h, followed by quantitative recovery of thevirus. Thirty min after mixing, uncooked, cooked, andbaked rice, and rice mixed with vegetable oil showed titersof 10(6.2), 10(7.2), 10(6.6), and 10(7.0) EID50/0.1ml, respectively.After storage for 24h at 22-25oC, the titers dropped to10(5.0), 10(6.5), 10(5.0), and 10(6.0) EID50/0.1ml for uncooked,cooked, baked, and oiled rice, respectively.

Resposta imune conferida pelas amostras La Sota e VG/GA do vírus da doença de Newcastle / Immune response conferred by La Sota and VG/GA strains of the Newcastle Disease Virus

Estudou-se a resposta imune de aves infectadas experimentalmente com amostras lentogênicas do vírus da doença de Newcastle (VDN), incluindo uma amostra com tropismo para o sistema respiratório e outra com tropismo entérico. Foram utilizadas as vias ocular, nasal, água de bebida e aspersão para a inoculação das amostras virais. A pesquisa foi realizada em 1.600 aves de linhagem para corte, divididas em oito grupos, de acordo com a amostra do vírus e a via de inoculação. Dez aves de cada grupo foram sacrificadas semanalmente. A resposta imune foi avaliada pela determinaçäo de anticorpos por ELISA e inibição da hemaglutinação. Os grupos inoculados com a amostra La Sota exibiram níveis mais elevados de anticorpos anti-VDN, superiores aos dos grupos inoculados com a amostra VG/GA. A resposta anamnéstica foi mais baixa para a amostra VG/GA inoculada pela água de bebida, e os níveis mais elevados de anticorpos circulantes, no pré-desafio, näo impediram a infecçäo pelo vírus