Genotypes II and VIId-based inactivated Newcastle disease vaccine reduces virus shedding
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In Egypt, recent outbreaks were reported in NDV-vaccinated flocks. The isolated strain was characterized as class II velogenic genotype VIId of Newcastle disease virus (NDV). In this study, three inactivated NDV vaccine formulations were prepared, the first one is LaSota (genotype II), the second one is genotype VIId and the third one is combined Lasota and genotype VIId at a proportion of 1:1. The challenge trials were conducted in SPF chicks to evaluate the efficacy of the prepared vaccines using 106 EID50/0.5 ml of the Egyptian genotype VIId strain of Newcastle disease virus (NDV-B7-RLQP-CH-EG-12). Our results revealed that all three prepared vaccine formulations conferred 100% protection in the vaccinated chicks. However, the combined vaccine induced the highest haemagglutination inhibition (HI) titers and neutralization indices with significant reduction in virus shedding compared to other vaccine formulations. Histopathology examination of different organs collected from vaccinated chicks post challenge indicated the protective efficacy in vaccinated groups compared to the positive control group where a score of severe lesions was shown. This study reports the efficacy of combined inactivated Lasota and genotype VIId vaccine in reducing virus shedding which is very important in controlling NDV infection in chicken.
KeywordsNeutralization index NDV genotype VIId Cross protection Real time PCR NDV shedding
We are grateful for all Staff members of Newcastle Department, Veterinary Serum and Vaccine Research Institute (VSVRI), Cairo, Egypt for their great help during the study.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The use of animals and protocols were approved by the Animal Care and Use Committee of Veterinary Serum and Vaccine Research Institute, Egypt.
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