الفهرس 
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Abstract
Bovine Salmonellosis is a worldwide bacterial disease causing great zoonotic impact, animal losses and economic problems. The present study was conducted on a total number of 313 samples divided into, 188 milk samples (124 from bulk tank milk and 64 from individual mastitic milk) and 125 fecal samples (100 diarrheic fecal samples and 25 from apparently normal calves in contact with the diseased ones) which collected from different localities of governorates in Egypt. Samples were examined bacteriologically and serologically, revealed that Salmonella was isolated in young diarrheic calves and apparent normal calves in 11% and 4% respectively, while mastitic caws exhibited 3.1% positive results and from bulk tank milk 3.2%. Serological examination18 of Salmonella isolates were typed as 15 S. typhimurium, two as S. sekondi and only one as S. chester in percentage of 83.3%, 11.1% and 5.6% respectively. Epidemiological studies showed that some risk factors as (age, sex, housing, and hygiene) have significant effect on Salmonella prevalence. Statistical analysis showed that there were significant results .The highest rate of salmonellosis was recorded in small animals and in bad hygienic farms specially containing rodents and steer animals. Conventional PCR was performed on 18 Salmonella isolates for the presence of seven virulence genes (invA, bcfC, stn, pefA, mgtC, csgD, and fimH). These genes were detected in 18 (100%), 18(100%), 16(88.9%), 14(77.7%), 3(16.7%), 1(5.5%) and 0(0%) respectively. In conclusion, Salmonella is one of the most important causes of diarrhea in calves and in adult cattle causing mastitis. The application of PCR assay is important for rapid detection of virulence profile of Salmonella.