Brucellosis

IntroductionBrucellosis, a zoonotic infectious disease caused by bacteria of the genus Brucella, remains a significant global health concern in many parts of the world. Traditional diagnostic methods, including serological tests, suffer from limitations, including low sensibility and high false-positive rates, emphasizing the need for improved diagnostic strategies. In this study, we aimed to optimize diagnostic accuracy by reevaluating serological tests and exploring novel diagnostic algorithms.MethodsA retrospective observational study was conducted using sera collected between June 2012 and June 2023 at the French National Reference Center for Brucella. Various serological tests, including Rose Bengal plate test (RBT), standard agglutination test (SAT), Brucellacapt, and ELISA for IgM and IgG, were performed. Different diagnostic algorithms were evaluated, combining RBT with SAT, Brucellacapt, and ELISA to enhance the performance of diagnostic tests.ResultsAmong 3587 sera analyzed, 148 were confirmed cases of human brucellosis. Individual serological tests exhibited good sensitivity and specificity but lacked diagnostic accuracy. However, combining RBT with SAT or Brucellacapt significantly improved diagnostic performance, with reduced false positives. The most promising results were observed when an algorithm was built combining RBT, Brucellacapt, and ELISA for IgM and IgG (a score value of 0.5 with 90.5% for sensitivity, 99.7% for specificity, 92.4% for PPV, and 99.6% for NPV).ConclusionsSerological tests remain crucial for brucellosis diagnosis, but their limitations necessitate innovative diagnostic approaches. Combining multiple serological tests in diagnostic algorithms shows promise in improving diagnostic accuracy. Efforts to refine diagnostic, strengthen surveillance, and raise awareness are essential for effective brucellosis control, particularly in resource-limited settings.

Brucellosis is a recognized zoonotic disease caused by various Brucella species with significant economic and animal welfare ramifications worldwide. The spread of brucellosis from domestic livestock and wild animals, as well as its emergence in new regions, present novel epidemiological challenges. The consumption of unpasteurized milk and dairy products from unsanitary farms in endemic areas poses a serious risk to public health from brucellosis. Determining the accurate prevalence of brucellosis, particularly in regions with persistently high prevalence, basically requires careful and frequent surveillance. Furthermore, transmission and detection of the illness in non-endemic areas have become more complex due to global human and animal migration as well as the trade in animal products. This review presents an updated understanding of brucellosis, covering its classification and taxonomy, pathogenesis, diagnosis and treatment approaches, epidemiology, available control and prevention measures, antimicrobial resistance and the role of metal uptake in bacterial virulence. It highlights the consequences of brucellosis for global health and underscores the need for continuous research, knowledge sharing, and interdisciplinary cooperation for effective disease control and prevention.

Diagnosis of brucellosis is not a straightforward task, with over 40 different tests available. Accurate diagnosis requires a series of diagnostic testing with proper interpretation of results. The World Organization for Animal Health (WOAH) provides guidelines describing the different assays including their recommended use, protocols, and interpretation. PubMed, Embase and Web of Science databases were searched without restrictions and original work describing cross-sectional studies focusing on livestock species (cattle, buffaloes, sheep, goats and swine) were included while reviews, case reports, and case-control studies were excluded. In this study, we systematically reviewed the literature and critically assessed the findings from 349 research studies to provide an overview of the different diagnostic methods used worldwide in livestock, and compared the tools and strategies used against the WOAH recommendations. A total of 232 studies (66.5%) focused on cattle followed by goats (34.1%), sheep (31.5%), buffaloes (14.6%), and swine (5.2%). Of these studies, 171 were from Africa (48.9%), 132 from Asia (37.8%), 36 from the Americas (10.3%), and 10 from Europe (2.8%). The most utilized immunological assayswere Rose Bengal test and indirect ELISA (63.9 and 36.7%, respectively). Interestingly, 73 studies (20.9%) used a single immunological assay to report on the status of animals. Direct methods such as culture and PCR were performed in 100 studies (28.7%) with culture being the most utilized (19.8%). Strikingly, we found that only 16% of included studies followed WOAH recommendations in terms of sample chosen, diagnostic assay utilized, protocol employed and results interpretation. In countries that reported the presence of B. abortus, B. melitensis, and B. suis to the WOAH, only 4 of 28, 2 of 19, and 1 of 6 countries (reporting these strains, respectively), contained studies that followed guidelines and confirmed the presence of the pathogen. This highlights, not only significant gaps in currently available literature leading to an inaccurate picture of brucellosis in livestock, but most importantly raises significant issues regarding the accuracy of data reported by countries. These findings are concerning due to the significant consequences of not adhering to these guidelines including inaccurate diagnosis, delayed disease control, and increased zoonotic risk for exposed individuals.

BackgroundBrucellosis poses a significant threat to animal and human health globally. However, how Brucella subverts the immune response to establish persistent infections remains unclear.MethodsWe utilized single-cell RNA sequencing (scRNA-seq) to decipher the immune landscape of mice infected with Brucella abortus. Flow cytometry, a transgenic cell line and mouse, and antibody blockage were utilized to explore the relevant mechanisms.ResultsBrucella infection induced significant changes in the composition and signaling pathways of immune cells, and flow cytometry analysis further confirmed the scRNA-seq data. An in-depth analysis of macrophages, the main target cell for Brucella, demonstrated activation of type I interferon (IFN) and type II IFN signaling, tumor necrosis factor production, diverse cell deaths, etc. Specifically, Vir-2308 Brucella infection induced IFN-β expression, primarily originating from macrophages. In vitro, a significantly lower level of intracellular Brucella survival was observed in ifnar1-/- macrophages. In vivo, ifnar1 genetic deficiency rendered the mice less susceptible to Brucella challenge resulting in a lower bacterial load and higher levels of macrophages and neutrophils. Interestingly, Brucella infection induced a dramatic reduction of NK cells along with the upregulation of CD94:NKG2A, one typical immune checkpoint module of NK cells. Further blockage of the NKG2A receptor in mice significantly reduced the bacterial load in the tissues, concurrent with a higher ratio of mature dendritic cells and a lower proportion of B cells.ConclusionsscRNA-seq revealed that Brucella infection significantly alters the immune microenvironment in mice, providing insight into a better understanding of brucellosis pathogenesis and the immune evasion strategies of this sophisticated pathogen.