Molecular evidence of Brucella abortus associated reproductive failure in domestic swine- an unexplored field study in Southern India

Brucellosis is an infectious bacterial zoonotic disease of domestic and wild animals frequently caused by Brucella abortus, B. ovis, B. melitensis, B. suis, and B. canis species. The present study was conducted on 100 serum samples from swine with a history of abortion and reproductive failure in the southern states of India. The samples were screened by Rose Bengal plate agglutination test (RBPT) and standard tube agglutination test (STAT) for detection and quantification of brucella antibody respectively. The samples were also subjected to 16S rRNA gene and Brucella cell surface salt-extractable (BCSP 31) based PCR assays for Brucella genome screening and confirmation. Brucella genome-positive samples were also subjected to AMOS multiplex PCR for B. abortus, B. ovis, B. melitensis, and B. suis species differential diagnosis. The serological screening revealed 3% (n=3) seropositivity for Brucellosis with antibody tires of 1: 160, 1:160, 1:320 for TL7, TL12 and KA-9 samples respectively. Molecular screening evidenced 5% (n=5) positivity for the Brucella genome including three seropositive samples yielded a specific amplicon of 800 and 223 bp amplicons by 16S rRNA and BCSP-31 PCR respectively. Further species identification by AMOS PCR yielded an amplicon of 498 bp specific to B. abortus genome in all three seropositive samples (TL7, TL12, and KA-9) and two PCR-positive samples (TN17 and KA-21) yielded 285bp amplicon specific to B. suis. Molecular screening of Brucella-positive samples for viral co-infections such as PCV2, PPV, CSFV, and PRRSV evidenced non-involvement of above screened 4 viral aetiologies in all 5 Brucella-positive samples indicating the primary infection of Brucella species.