Detection of the Newcastle disease virus and its effect on development of post-vaccination immunity in a commercial flock of laying hens

The aim of this study was to monitor the concentration of antibodies against Newcastle disease after vaccination of laying hens at the beginning and in the end of the laying period. The study was carried out in one commercial flock of laying hens in Opatovice in the Czech Republic in the years 2008-2010. A total of 280 samples of blood sera were taken from laying hens coming from four poultry houses. The sera were tested by the haemagglutination inhibition test according to the OIE Manual. Virological testing was conducted as a consequence of atypical results of serological testing. Newcastle disease virus RNA was proved by the RT-nested PCR method in the pooled tissue samples of 5 hens, in the samples of intestines with ileocaecal tonsila, in trachea and also in one swab sample from the environment of one house. Based on sequencing analysis and subsequent phylogenetic analysis, the virus was identified as a low pathogenic strain of paramyxovirus (PMV-1). This low pathogenic strain did not have any impact on the health of laying hens.