الفهرس 
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Abstract
Bovine tuberculosis is an infectious disease of domestic and wild animals caused by Mycobacterium bovis which develops an economically important disease in dairy cattle farms in Egypt. A cross-sectional study to determine the prevalence and identify the risk factors of bovine tuberculosis (BTB) was carried out from November, 2015 to April, 2018 using comparative intradermal tuberculin (CIDT) test, postmortem examination, bacteriological examination and indirect enzyme linked immune-sorbent assay (I-ELISA). A pre-tested structured questionnaire was used to collect data on herd size, management, body condition score, and housing system. A total of 5327 dairy cattle in 16 dairy herds in mid-Delta, Alexandria road and Upper Egypt districts were examined using comparative intradermal tuberculin (CIDT) test where the herd and individual animal prevalence at cut-off ≥4mm were 68.75% (95%, CI: 46 to 91.4) and1.67% (95%, CI: 1.3to 2.1) respectively. The herd prevalence varied according to location and the highest result was in the mid-Delta district, which was 75%. The individual prevalence was significantly associated with location mainly in mid-Delta district (OR. 3.63, P=0.0001), age of animals: mainly 3-6 years (OR. 6.57, P=0.0001), breed mainly Holstein Friesian (OR. 5.24, P=0.0209) and density of cattle in the yard (OR. 3.01, P=0.000). On herd level, history of BTB in the farm (OR. 18, P= 0.036), management condition (OR. 18, P= 0.036), raising different species in the same facility (OR. 41.8, P=0.005), purchase of new animals (OR. 40, P=0.005) and not associated with the herd size (OR. 7, P=0.141) and history of BTB in the neighboring farms (OR. 3.33, P=0.346). The postmortem examination of positive reactors revealed 66 (85.71%) out of 77 slaughtered cattle with visible lesions classified as 8(12.12%) generalized, 26 (39.40%) pulmonary, 3 (4.54%) digestive, 11 (16.67%) mixed and 18 (27.27%) head) while 11 (14.29%) with Non-visible lesions. Bacteriological examination revealed that 74.24% (49/66) from visible lesions and 9.09% (1/11) from non-visible lesions as Mycobacterium bovis. The indirect enzyme linked immune-sorbent assay (I-ELISA) revealed that 31 (40.26%) showed positive results, including 29 (93.6%) visible lesions and 2 (6.4%) of non-visible lesions. In conclusion, the prevalence of bovine tuberculosis is high in herds with poor management conditions, raising different species in the same facility, had previous history of BTB infection and purchasing new animals. At the individual level, Holstein breeds aged 3-6 years, kept in high density, and located in mid-Delta district were more likely to be positive for bovine tuberculosis.