genomic detection of brucella spp in seropositive cattle in charmahal va bakhtiyari province, iran

background: brucellosis is one of the most common zoonosis in middle east and iran. objectives: the purpose of this study was genomic detection of brucella spp. in sero-positive dairy cattle. methods: 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: 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. conclusions: 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.