Decreasing prevalence of brucellosis in red deer through efforts to control disease in livestock.

When a pathogen infects a number of different hosts, the process of determining the relative importance of each host species to the persistence of the pathogen is often complex. Removal of a host species is a potential but rarely possible way of discovering the importance of that species to the dynamics of the disease. This study presents the results of a 12-year programme aimed at controlling brucellosis in cattle, sheep and goats and the cascading impacts on brucellosis in a sympatric population of red deer (Cervus elaphus) in the Boumort National Game Reserve (BNGR; NE Spain). From February 1998 to December 2009, local veterinary agencies tested over 36 180 individual blood samples from cattle, 296 482 from sheep and goats and 1047 from red deer in the study area. All seropositive livestock were removed annually. From 2006 to 2009 brucellosis was not detected in cattle and in 2009 only one of 97 red deer tested was found to be positive. The surveillance and removal of positive domestic animals coincided with a significant decrease in the prevalence of brucellosis in red deer. Our results suggest that red deer may not be able to maintain brucellosis in this region independently of cattle, sheep or goats, and that continued efforts to control disease in livestock may lead to the eventual eradication of brucellosis in red deer in the area.

Evaluation of a PCR test for the diagnosis of Brucella ovis infection in semen samples from rams.

The sensitivity and specificity of a PCR assay with primers derived from the insertion sequence IS6501 was compared with that of bacteriological culture and serological tests for the diagnosis of Brucella ovis infection in rams. No amplifications were detected with DNAs from the strains phylogenetically related to Brucella and from the seven bacterial species considered as the main etiologic agents of epididymitis in rams. In addition, the specificity of the PCR was 100% when testing semen samples from Brucella-free rams. The comparison of the semen culture and PCR results from 192 semen samples tested, showed a proportion of agreement of 0.91 between both tests. The PCR-based test described has sensitivity similar to that of semen culture and could be used as a complementary test for the direct diagnosis of Brucella ovis in semen samples of rams.

Diagnosis of Brucella ovis infection of rams with an ELISA using protein G as conjugate.

The complement fixation and gel diffusion tests for Brucella ovis ram epididymitis were compared with an indirect ELISA using antigens from B ovis extracted in hot saline, rough B ovis lipopolysaccharide or a cytosolic fraction of rough B melitensis 115, and commercial anti-IgG (heavy and light chain specificity) or protein G conjugates. None of the antigens and conjugates used in the ELISA gave better results in terms of sensitivity and specificity than the complement fixation or the gel diffusion tests with the sera of 41 rams naturally infected with B ovis, 17 rams inoculated conjunctivally with B ovis and 53 Brucella-free rams. The protein G conjugate significantly reduced the background reactivity of the sera from the Brucella-free rams but did not improve the sensitivity of the ELISA with the anti-IgG conjugate.