Polyphasic Characterization of Brucella spp. in Livestock Slaughtered from Abattoirs in Eastern Cape, South Africa

Abstract

In livestock, brucellosis is mainly an asymptomatic disease except when abortion occurs; therefore, two serological tests are used for diagnosis as no single test is suitable. Abattoir samples enable a combination of culture, molecular, and serological tests to detect brucellosis. This study assessed <i>Brucella</i>-specific PCR (ITS-PCR) to detect brucellosis and to conduct a molecular characterization of <i>Brucella</i> spp. isolated from PCR-positive livestock (n = 565) slaughtered at abattoirs and the appropriate sample tissue(s). ITS-PCR detected <i>Brucella</i> DNA in 33.6% of cattle, 14.5% of sheep, and 4.7% of pig tissues. Impure <i>Brucella</i> cultures from PCR-positive tissues were 43.6% (44/94) of cattle, 51.7% (15/29) of sheep, and 50% (2/4) of pigs with predominantly <i>B. abortus</i> identification with AMOS-PCR and low isolation of mixed <i>B. abortus</i> and <i>B</i>. <i>melitensis</i> in all species. In cattle, 33% of isolates were from lymph nodes, while in sheep 38.0% were from the liver and kidney and only from tonsils in pigs (2/4). <i>Brucella</i> infections identified with AMOS-PCR were present in seropositive and mainly seronegative (75.6-100%) livestock with the potential to cause brucellosis during pregnancy or breeding. This study demonstrated the value of the polyphasic approach, especially with chronic infections and the potential risk of these asymptomatic animals.