TRANSMISSIBLE VIRAL PROVENTRICULITIS AND STUNTING SYNDROME IN BROILER CHICKENS IN EGYPT: 1. ISOLATION AND CHARACTERIZATION OF VARIANT INFECTIOUS BURSAL DISEASE VIRUS (IBDV)

Document Type : Original Article

Authors

1 Department of Virology. Faculty of Veterinary Medicine, Cairo University, Giza-Egypt, 12211

2 Central laboratory for evaluation of Veterinary Biologics, Abassia-Cairo, Egypt

3 Department of poultry, Faculty of Veterinary Medicine, Tanta University, Egypt

Abstract

In the present study, 46 broiler chicken flocks (2 to 4 weeks of age and in farms located in four governorates were examined. They were affected with proventriculitis and stunting syndrome and were vaccinated with classical infectious bursal disease vaccines. Affected flocks generally showed stunting, reduced growth rate and uneven weight distribution. Necropsy of chicks revealed a high incidence of increased size of the proventriculus. Transmission and isolation studies of causative agent were undertaken in one-day-old SPF chicks using homogenates from proventriculus collected from 5 flocks from El-Fayoum governorate.  Gross and histological changes were observed in inoculated chicks for 2 weeks. In addition, sera collected from inoculated chicks at the end of the observation period were tested by ELISA for infectious bursal disease virus (IBDV), infectious bronchitis virus (IBV), Mycoplasma gallisepticum (MG), Mycoplasma synoviae (MS). chicken anemia virus (CAV), avian leucosis virus (ALV), avian leucosis virus Subgroup-J (ALV-J), reticuloendotheliosis virus (REV), Newcastle disease virus (NDV), avian rhinotracheitis virus (ARTV) and Reo virus. Proventricular homogenates were prepared from the inoculated chicks and inoculated for 2 more passages in SPF chicks. The results revealed that the inoculum was infectious and transmissible as judged by the induction of proventriculitis throughout the three passages in SPF chicks. Signs of anemia and immunosuppression (liver, spleen, bursa) were observed in necropsized chicks. Infectious bursal disease virus (IBDV) antibodies were detected in sera of inoculated chicks. Histopathological examination of organs (proventriculus, bursa, spleen, kidney and liver) from the inoculated SPF chicks revealed pathological changes described in details. IBDV was detected in bursae collected from inoculated chicks throughout the three passages using antigen capture ELISA, based on the use of a common VP2 epitope of IBDV. Antigenic typing of the isolated virus in bursae collected from the third passage using a panel of 3 monoclonal antibodies directed against VP2 epitopes of IBDV revealed that the isolated virus was related to Delaware (E/Del) variant strain of IBDV. The isolated IBDV was inoculated into non vaccinated commercial broiler chicks (6-8 days of age) that had maternally- derived IBDV antibodies (from breeders vaccinated with classical IBDV). The virus was detected in the bursa at 72 hours PI by ELISA and electron microscope confirming the persistence of the variant IBDV in the chicks despite the presence of IBDV classical antibodies. The present study reports for the first time the association of IBDV with stunting syndrome and proventriculitis in broilers in Egypt.

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