Genomic detection of Brucella spp in Seropositive cattle in charmahal va Bakhtiyari province, Iran

Brucellosis is one of the most common zoonosis in Middle East and Iran. The purpose of this study was genomic detection of Brucella spp. in sero-positive dairy cattle. We have collected 28,519 blood samples from cows during 2012-2013. Samples were screened by Slide and tube agglutination and 2-Mercaptoethanol tests. Samples with anti-Brucella antibodies titer ≥ 1:80 and ≥1:40 in tube agglutination and 2-ME tests were considered as positive respectively. Tissue samples include: lymph nodes, liver, testicle and kidney from 122 samples of slaughtered cows were collected. The Sero-positive samples were examined by a collection of specific primers for Brucella abortus, Brucella melitensis, vaccinal strains included RB51 and Rev1 using PCR tests. Results showed that 450 samples were positive in slide agglutination test and 447 samples had anti-brucella antibodies titer equal to or more than 1:80. So they were positive by tube agglutination test. Three hundred eighty nine samples were positive by 2- mercaptoethanol test. PCR test results showed that 46 samples (37.7%) out of 122 samples had a specific sequence of Brucella or otherwise they have an active infection with Brucella species, whereas 62.3% of samples were negative. The PCR results showed that 2 samples (4.35%) were infected by B. melitensis, 2 samples (4.35%) infected by Rev1 strain and 42 samples (91.3%) were infected by B. abortus. The results showed that, as we had expected, the majority of cows were infected by B. abortus. Animals who infected by B. melitensis and Rev1 strain may be a result of contact with sheep or goats. We couldn’t find Brucella genome in 76 samples (62.3%) of sero-positive cows. It may be caused by cross reaction of sera with Brucella species in tests or activation of immune system response and elimination of organism from internal organs.