Detection of brucellosis in occupationally exposed humans by molecular and serological techniques

Brucellosis is one of the most common zoonoses worldwide. It's diagnosis by isolation and identification is slow and has inadequate sensitivity. Sero-diagnosis is rapid and sensitive but lacks adequate specificity. The PCR based methods are suggested to overcome these disadvantages. We compared the efficacy of serology and PCR assays in detecting human brucellosis and studied the epidemiology of brucellosis in the occupationally exposed humans from selected locations in Maharashtra. Humans (n=121) with or without clinical brucellosis were screened serologically by Rose Bengal Plate Test (RBPT) and Standard Tube Agglutination Test (STAT). Eighty four of these subjects were simultaneously screened for the presence of Brucella spp. using PCR. Serologically, 19.83% of 121 humans were positive for the presence of antibodies against Brucella. The proportion of seropositive humans was greater in the locations from Western Maharashtra than Konkan region. Amplification of 223 bp product for BCSP31 was observed in 29 (34.52%) individuals whereas 17 subjects (20.23%) were found positive for IS711. None of the blood samples tested was positive for B. melitensis by IS711 BM PCR. Comparison of three detection methods revealed that the BCSP 31 PCR could detect greater number of positive samples than serology and IS711 AB PCR assay. Analysis of results of B. abortus specific IS711 AB PCR, that detects biovars 1, 2 and 4, suggested possibility of prevalence of different B. abortus biovars at different locations in Maharashtra. The BCSP31 PCR assay could be used as an adjunct to serology for confirmation of human brucellosis. This study suggests possibility of prevalence of different B. abortus biovars in different regions of Maharashtra.