الفهرس 
Introduction
Historical backgroundOnly 14 pages are availabe for public view
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Abstract
This study aimed to diagnosis of bovine coronavirus in calves. In the current study, a total of 107 fecal samples were collected from calves suffering from diarrhea from 1 day to 3 weeks of age from different localities in Dakahlia Governorate, Egypt (Gamasa, Belkas, Sherbin, Nabaroh, Talkha, Almanzala, Algamalia and Aga) during the period of (2015 to 2018). The fecal samples from 107 cases were screened for the presence of BCoV Ag by using Monoscreen Ag-ELISA Bovine coronavirus BIO K 344/2. from ELISA positive identified samples, we visualized the Coronavirus particles in a great number when negatively stained by transmission electron microscopy. Detection of BCoV by RT-PCR in the collected field samples using primers were designed to amplify (236 bp) fragment of N gene, this step was followed by partial Nucleotide sequence analysis of amplified N gene of the identified BCoV nucleic acid to study the molecular characterization of field isolate of BCoV circulating at Dakahlia Governorate. from ELISA and PCR positive identified samples, virus isolation was done via MDBK tissue culture for 7 days, six passages were carried out followed by identification of BCoV in harvested tissue culture via DFA test and indirect immunoperoxidase technique.
The results of ELISA and RT-PCR revealed that: out of 107 tested fecal samples, 4 samples showed positive results (3.7%) and 103 samples were negative (96.2%). By transmission electron microscope examination using negative staining method, The viral particles showed pleomorphism marked, rounded or elongated shaped, with characteristic radial projections forming a corona. BCoV CPE which developed in MDBK cells started with granular, swollen, or enlarged cells within 48h P.I. then the membranes of the enlarged cells were fused together to form syncytia then usually the rounded, swollen cells detached and with CPE progress, focal to diffuse. All tested samples gave positive results with direct FAT as yellowish green coloration was detected in stained MDBK cells which increased gradually with increased passages cytoplasmic vacuolation was prominent 4 to 7 days P.I. All tested samples gave positive results with IP as brownish coloration was detected in stained MDBK cells which increased gradually with increased the period of incubation. The multiple alignments of the N gene nucleotide sequences (236bp) of BCoV isolates compared with other BCoV isolates on the Genbank show substitution of nucleotide G instead of A at position 181. Change the codon sequence from ATG to GTG to code valine instead of methionine aminoacid at position 61.