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Molecular Diagnosis of Persistently Very Virulent Infectious Bursal Disease Virus at Sharkia Governorate, Egypt

Molecular Diagnosis of Persistently Very Virulent Infectious Bursal Disease Virus at Sharkia Governorate, Egypt

Hala Mohamed Nabil Tolba1, Naglaa Fathy Saeed Awad1*, Gamelat Kotb Farag Kotb2, Amany Adel3 

1Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; 2Department of Virology, Faculty of Veterinary Medicine, Zagazig University, Zagazig 44519, Egypt; 3Reference Laboratory for Veterinary Quality Control on Poultry Production, Animal Health Research Institute, Dokki, Giza 12618, Egypt.

NF2731982@gmail.com 

ABSTRACT

Severe outbreaks of Infectious bursal disease virus (IBDV) were reported in Egypt despite vaccination. Therefore, this study was conducted to characterize infectious bursal disease (IBD) viruses circulating in Egypt during the period of 2017 - 2018. Sixteen pooled bursal tissue samples were collected from IBD suspected (9 Egyptian balady and 7 broiler) chicken flocks located in different localities at Sharkia governorate, Egypt. These samples were subjected for direct detection of a 620 bp hypervariable region in the VP2 gene using Reverse transcriptase polymerase chain reaction (RT-PCR). The nucleotide and deduced amino acid sequences for VP2 hypervariable region of selected five IBDV field isolates were determined and compared to well characterized reference and vaccine strains worldwide. The IBD virus was detected in 9 out of 16 (56.25 %) investigated chicken flocks. Sequence analysis revealed that the analyzed Egyptian isolates identified as very virulent Infectious bursal disease virus (vvIBDV). The identity between these Egyptian isolates and the vaccine strains is ranged from 89.5%-95.6% and 88.1%-97.8% -at the nucleotide and amino acid sequence levels, respectively. The IBDV-Egy1 isolate is related to the Egyptian vvIBDV strains but with some deviations in the amino acids (259V, 263F, 290I and 302N). There were dramatic differences in the predictive antigenic determinants between these vvIBDV isolates and the classic vaccine strain (Bursin plus). These findings could explain the persistence of vvIBDV circulation in the Egyptian environment in spite of vaccination with classical vaccine strains.  

 

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Hosts and Viruses

June

Vol.6, Iss.3, Pages 42-84

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