Evaluation of Some Vaccination Programs in Protection of Experimentally Challenged Broiler Chicken against Newcastle Disease Virus

The current study was carried out to evaluate efficiency of different vaccination programs in protecting broiler chicken against Virulent Viscerotropic Strain of Newcastle disease virus. Different live and inactivated NDV vaccines were used throughout the experiment including; ND-HB1,Elite, LaSota, Inactivated GII and Inactivated GVII. Broiler chicks were divided into 8 groups; 6 groups undergo different vaccination programs against NDV while two groups were kept without vaccination to be the control groups. Challenge was done at day 30^th of age via intranasal administration of NDV velogenic GVII (NDV/CK/Egypt/567F/2012). Abs titers were determined at days 1, 7, 14, 21, 28 and 35 days of the experiment. The obtained results of shedding titers of NDV clarified that the lowest shedding titer was recorded in group vaccinated by HB + double shots of Inactivated GVII + Elite + LaSota and HB + double shots of Inactivated GII + Elite + LaSota, then group vaccinated by HB + one shot of Inactivated GVII + Elite + LaSota and HB + one shot of Inactivated GII + Elite + LaSota at days 3, 5, 7 and 9 post challenge day at 30^th, respectively compared to those vaccinated by live vaccines HB + LaSota only and HB + Elite + LaSota only. Also, no mortalities (100% protection rate) were recorded in groups vaccinated with both live and inactivated NDV vaccines compared to low mortality rates recorded in groups vaccinated with live vaccines only. Based on the recorded results, it was concluded that application of ND vaccination programs containing both live and double inactivated vaccines (either GII or GVII) was found to be more effective than those depending on one shot of inactivated vaccine (either GII or GVII) plus live vaccines and more effective than program including live vaccines only.