EFFECTIVENESS OF SINGLE AND DOUBLE RECOMBINANT HERPES VIRUS OF TURKEY VECTORED VACCINES BOOSTERED WITH LIVE ND VACCINE AGAINST THE HIGHLY PATHOGENIC NEWCASTLE DISEASE VIRUS GENOTYPE VII

Document Type : Case report

Authors

1 Avian and Rabbit Diseases Department, Faculty of Veterinary Medicine, Benha University, Moshtohor 13736, Qalyubia, Egypt

2 Histology Department, Faculty of Veterinary Medicine, Benha University, Egypt

3 Central Laboratory for Evaluation of Veterinary Biologics. Agriculture Research Centre

Abstract

This study assesses the effectiveness of recombinant Newcastle disease vaccine formulations in one-day-old specific pathogen-free (SPF) chicks, with an emphasis on their performance against the current circulating NDV strain (Egypt-NDV-RLQP-2021) in Egypt. A total of 100 SPF chicks were divided into five groups; Group 1 received INNOVAX-ND-IBD®, Group 2 was given Vaxxitek ® HVT + IBD + ND, and Group 3 was vaccinated by Vectormune® ND, which utilized the herpesvirus of turkeys (HVT) as a vector by integrating the fusion (F) gene from Newcastle disease virus (NDV) into the HVT genome. Vaccinated groups received a single dose of live clone NDV genotype II vaccine at 15 days of age via intraocular instillation. Group 4 was kept as the positive control (no vaccination, challenged with NDV), and Group 5 was the negative control. Groups 1, 2, 3, and 4 were challenged 28 days later with virulent NDV genotype 7 with 0.2 mL 106 EID50 of a challenge virus intramuscularly. Chicks were monitored for clinical signs, mortality, and viral shedding using real-time PCR. Histopathological findings proved that all vaccinated groups showed good control in masking and preventing lesions compared to the positive control group 4. Serology examinations indicated a significant increase in antibody titer post-vaccination and challenge in all vaccinated groups, giving a protective immunity against NDV. For viral shedding, Group 2 showed no detectable virus at any time, which means superior control for viral shedding. In conclusion, our study highly recommends HVT-based vaccines together with NDV live vaccines, as they exhibited full clinical protection against NDV genotype VII.

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