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Abstract
Seroprevelance of pestiviruses in 40 sheep flocks with a total density of 7500 heads within El-Minia and Beni-Suef Governorate was performed using ELISA. S/P ratio method was used to detect antibody titers. All the examined flocks were found positive for pestiviruses and high overall prevalence rate was recorded in this study as 370 out of 700 examined animals were found to be positive for pestiviruses antibodies.
Nine ovine and caprine foeti and/or neonates were collected during the course of this study. The clinical data of the animals were highly suggestive of pestivirus infections. Detection of pestivirus antigen was perforemed on different tissues from the examined animals by Immunohistochemistry (IHC) using either polyclonal antibodies raised against BDV or five different monoclonal antibodies targeting different epitopes on the structural proteins Erns and E2 of pestiviruses. While Two out of nine examined animals showed positive staining by IHC for pestiviruses in brain tissue, none gave positive results with the Mabs used. Brain and pooled tissue homogenates were inoculated on MDBK in an attempt for virus isolation. One virus isolate has been isolated and this virus was confirmed to be a pestivirus by IFA using anti-BVDV FITC- conjugate. This isolate showed clear CP effects on MDBK after it was passaged blindly for 5 times on MDBK cells.
To molecularly characterize the Egyptian pestivirus isolate which assigned the name BSU1, RT-PCR was done for 3 different genomic regions which are 5’-UTR, polyprotein and E2 genes. Products of expected sizes were seen by agar gel electrophoresis. Sequence of the PCR products was performed in the three genomic regions and sequences were submitted to GenBank and assigned the accession No. GU085506 for 5’-UTR and GU991550 for polyprotein genomic region while E2 sequence not submitted yet. For Sequqnce analysis, three genomic regions were used; 5’-UTR, Npro and E2 gene. Phylogenetic trees constructed using aligned sequences of the Egyptian isolate and reference strains of pestiviruses confirmed the pestivirus isolate to be classified as BVDV-1 falling in BVDV-1b branch. CLUSTAL W multisequence analyses were performed for the 5’-UTR, Npro and E2 gene suggesting that genetic organization of this virus was similar to the remaining BVDV-1 isolates as well as to other pestivirus isolates analyzed so far. It was also found that the Egyptian BVDV isolate is closed to the German BVDV-1b isolates. The genetic examination of the isolate BSU1 showed that most variability within BVDV-1 isolates was found within the E2 gene. This finding was plausible, since E2 gene encoding envelope protein is the gene with a high mutation rate also in other pestivirus isolates as well. To our knowledge, this is the first report of isolation of a pestivirus from goats in Egypt and the second report worldwide on isolation of pestivirus from goat kid showing typical central nervous signs of border disease.