Abstract
Bovine brucellosis is an infectious disease caused mainly by Brucella abortus; however, B. melitensis and occasionally B. suis may infect cattle. In Argentina brucellosis has been controlled in most of the cattle; however, routine serological surveillance detects animals which are positive on standard serological tests with low titers that are persistent or in many cases become negative later. In the geographic zone known as “La pampa” where most of the Argentinian cattle are concentrated, bovines share the habitat with wildlife present in the region. Previous documents indicate that in animals like armadillo and hares, the prevalence of Brucella antibodies is 16 and 6 % respectively. Interestingly, only B. suis biovar 1 has been isolated from those species. The objective of this research was to evaluate the serological pattern of heifers challenged with 1.5×107 IC of three different strains of B. suis biovar 1. Twelve pregnant cows, 2 years old, were utilized.Three of them (group A) were inoculated with B. suis isolated from armadillo; 3 heifers were challenged with B. suis isolated from hare; 3 were challenged with B. suis 1330; and 3 animals (group 4) were not challenged as a control. Blood was collected prior to challenge and every 20 days until the end of the study 150-day post challenge. For serological analysis, the Buffer plate antigen test (BPAT) was used as a screening test and fluorescent polarization (FPA) as the confirmatory test. All animals were negative 20 days before and the same day of challenge. All animals in group A and C, as well as two animals from group B were positive on BPA and FPA after challenge and remained so until day 60. Two heifers, one from group A and another from group B, persisted as positive until the end of the experiment (day 150) with high titers on the FPA test. All animals delivered their calves normally. We concluded that in this experiment B. suis inoculated into pregnant animals does not cause abortions but does induce serological titers which interfere the with test results and may cause confusion with the status of this animals.
