Clinical and histological features of brucellin skin test responses in Brucella suis biovar 2 infected pigs

Environment and Offspring Surveillance in Porcine Brucellosis

Porcine brucellosis, caused by Brucella suis (B. suis), is a notifiable disease causing significant economic losses in production systems. Most infected pigs may act as carriers and shed B. suis even if asymptomatic. This can contribute to environmental persistence, thus hindering control efforts. Here, the environment and the offspring were investigated during and after a B. suis outbreak at a sow breeding farm. The diagnosis of B. suis in sows (n = 1,140) was performed by culture and polymerase chain reaction (PCR) from vaginal swabs, indirect enzyme-linked immunosorbent assay (I-ELISA) from sera, and brucellin skin test (BST). B. suis diagnosis in post-weaning pigs (n = 899) was performed by I-ELISA in sera and BST. The environmental surveillance programme was implemented by placing gauze sponges (n = 175) pre-hydrated in a surfactant and inactivating liquid for Brucella DNA detection by PCR in different farm areas. Our results showed that the offspring of infected sows reacted to in vivo techniques for B. suis. Furthermore, the offspring born during the outbreak displayed higher seropositivity (I-ELISA) and reactivity (BST) than those pigs born after. Brucella DNA was detected in pregnant sow areas, boxes, boots, and post-weaning pig areas. In addition, Brucella DNA environmental detection was higher during the B. suis outbreak than the post B. suis outbreak. The environmental approach has proven to be a simple, practical, valuable, and safe method to detect and monitor B. suis. These results suggest a role of the environment and the offspring that should be considered in porcine brucellosis surveillance and control programmes.

Establishment and Initial Testing of a Medium-Sized, Surgically Feasible Animal Model for Brucellar Spondylodiscitis: A Preliminary Study

Brucellar spondylodiscitis, the most prevalent and significant osteoarticular presentation of human Brucellosis, is difficult to diagnose and usually yields irreversible neurologic deficits and spinal deformities. However, no animal models of Brucellar spondylodiscitis exist, allowing for preclinical investigations. The present study investigated whether intraosseous injection of attenuated Brucella melitensis vaccine into rabbits' lumbar vertebrae imitates the radiographic and histopathological characteristics of human Brucellar spondylodiscitis. Radiographic and histopathological analyses at 8 weeks postoperatively revealed radiographic changes within vertebral bodies and intervertebral discs, abscesses formation within the paravertebral soft tissue, and typical prominent inflammation response without caseous necrosis, which were largely comparable to human Brucellar spondylodiscitis. Such a medium-sized, surgically feasible rabbit model provides a promising in vivo setting for further preclinical investigation of Brucellar spondylodiscitis.

Efficacy of antibiotic treatment and test-based culling strategies for eradicating brucellosis in commercial swine herds

Swine brucellosis caused by Brucella suis biovar 2 is an emerging disease in continental Europe. Without effective vaccines being available, the European Food Safety Authority (EFSA) recommends the full depopulation of infected herds as the only strategy to eradicate B. suis outbreaks. Using data collected from 8 herds suffering natural swine brucellosis outbreaks, we assessed the efficacy of four control strategies: (i) oxytetracycline treatment only, as a default scenario, (ii) oxytetracycline treatment combined with skin testing and removal of positive animals, (iii) oxytetracycline treatment combined with serological testing (Rose Bengal test-RBT-and indirect ELISA -iELISA-) and removal of seropositive animals and (iv) oxytetracycline treatment combined with both serological (RBT/iELISA) and skin testing and removal of positive animals. A Susceptible-Infectious-Removal model was used to estimate the reproduction ratio (R) for each strategy. According to this model, the oxytetracycline treatment alone was not effective enough to eradicate the infection. However, this antibiotic treatment combined with diagnostic testing at 4-monthly intervals plus immediate removal of positive animals showed to be effective to eradicate brucellosis independent of the diagnostic test strategy used in an acceptable time interval (1-2 years), depending on the initial number of infected animals.