Pathogenesis of bovine brucellosis

Insights into the effect of guanylate-binding protein 1 on the survival of Brucella intracellularly

Brucellosis is a zoonotic disease that affects wild and domestic animals. It is caused by members of the bacterial genus Brucella. Guanylate-binding protein 1 (GBP1) is associated with microbial infections. However, the role of GBP1 during Brucella infection remains unclear. This investigation aimed to identify the association of GBP1 with brucellosis. Results showed that Brucella infection induced GBP1 upregulation in RAW 264.7 murine macrophages. Small interfering GBP1 targeting RNAs were utilized to explore how GBP1 regulates the survival of Brucella intracellularly. Results revealed that GBP1 knockdown promoted Brucella's survival ability, activated Nod-like receptor (NLR) containing a pyrin domain 3 (NLRP3) and absent in melanoma 2 (AIM2) inflammatory corpuscles, and induced pro-inflammatory cytokines IFN-γ and IL-1β. Furthermore, Brucella stimulated the expression of GBP1 in bone marrow-derived macrophages (BMDMs) and mice. During the inhibition of GBP1 in BMDMs, the intracellular growth of Brucella increased. In comparison, GBP1 downregulation enhanced the accumulation of Brucella-induced reactive oxygen species (ROS) in macrophages. Overall, the data indicate a significant role of GBP1 in regulating brucellosis and suggest the function underlying its suppressive effect on the survival and growth of Brucella intracellularly.

Neurobrucellosis (Brucella ceti) in striped dolphins (Stenella coeruleoalba): Immunohistochemical studies on immune response and neuroinflammation

Neurobrucellosis is a shared condition of cetaceans and humans. However, the pathogenesis and immune response in cetacean neurobrucellosis has not been extensively studied. In this multicentric investigation, 21 striped dolphin (Stenella coeruleoalba) neurobrucellosis (Brucella ceti) cases diagnosed over a 10-year period (2012-2022) were retrospectively evaluated. For each case, morphological changes were assessed by evaluating 21 histological parameters. Furthermore, the immunohistochemical expression of Brucella antigen, glial fibrillary acid protein (GFAP), and a selection of inflammatory cell (IBA-1, CD3, and CD20) and cytokine (tumor necrosis factor-alpha [TNF-α], interferon-gamma [IFN-γ], interleukin [IL]-1β, IL-2, and IL-6) markers were investigated. Inflammation of the leptomeninges, ependyma, and/or choroid plexus was lymphohistiocytic, containing macrophages/microglia (IBA-1+), T-cells (CD3+), and B-cells (CD20+) in equal proportion. B-cells occasionally formed tertiary follicles. GFAP expression showed astrocytosis in most cases. Expression of TNF-α, IFN-γ, and IL-2 indicated an intense proinflammatory response, stimulating both macrophages and T-cells. Our results showed that the inflammation and neuroinflammation in neurobrucellosis of striped dolphins mimic human neurobrucellosis and in vitro and in vivo studies in laboratory animals. Cetacean disease surveillance can be exploited to expand the knowledge of the pathogenesis and immunology of infectious diseases, particularly brucellosis, under a One Health approach.

A novel Bayesian Latent Class Model (BLCM) evaluates multiple continuous and binary tests: A case study for Brucella abortus in dairy cattle

Bovine brucellosis, primarily caused by Brucella abortus, severely affects both animal health and human well-being. Accurate diagnosis is crucial for designing informed control and prevention measures. Lacking a gold standard test makes it challenging to determine optimal cut-off values and evaluate the diagnostic performance of tests. In this study, we developed a novel Bayesian Latent Class Model that integrates both binary and continuous testing outcomes, incorporating additional fixed (parity) and random (farm) effects, to calibrate optimal cut-off values by maximizing Youden Index. We tested 651 serum samples collected from six dairy farms in two regions of Henan Province, China with four serological tests: Rose Bengal Test, Serum Agglutination Test, Fluorescence Polarization Assay, and Competitive Enzyme-Linked Immunosorbent Assay. Our analysis revealed that the optimal cut-off values for FPA and C-ELISA were 94.2 mP and 0.403 PI, respectively. Sensitivity estimates for the four tests ranged from 69.7% to 89.9%, while specificity estimates varied between 97.1% and 99.6%. The true prevalences in the two study regions in Henan province were 4.7% and 30.3%. Parity-specific odds ratios for positive serological status ranged from 1.2 to 2.2 for different parity groups compared to primiparous cows. This approach provides a robust framework for validating diagnostic tests for both continuous and discrete tests in the absence of a gold standard test. Our findings can enhance our ability to design targeted disease detection strategies and implement effective control measures for brucellosis in Chinese dairy farms.

The Reasons Behind Long-Term Endemicity of Brucellosis in Low and Middle-Income Countries: Challenges and Future Perspectives

Brucellosis is a neglected worldwide zoonotic disease with more than 500,000 new human cases each year. Direct contact with infected animals and consumption of undercooked animal origin foods are the main routes of brucellosis transmission to humans. Although long endeavor has been applied to control and eliminate brucellosis from animal and human populations in developing countries especially in low- and middle-income countries (LMICs), the disease is still endemic in these regions. Many common or unique factors including raw milk consumption, unhygienic slaughter of livestock, extensive husbandry, budgetary limitations, misdiagnosis, and other conditions play a role in long-term endemicity of brucellosis in these locations. It has been shown that One Health is the only practical approach to control brucellosis; however, applying such methods is challenging in low-resource areas. In such conditions, brucellosis is continuously maintained in animals and repeatedly spread to human populations. In this article, factors playing a critical role in brucellosis endemicity, and the real conditions challenging the application of One Health approach in control of brucellosis are highlighted.

Immune Responses Potentially Involved in the Gestational Complications of Brucella Infection

Infection by Brucella species in pregnant animals and humans is associated with an increased risk of abortion, preterm birth, and transmission of the infection to the offspring. The pathogen has a marked tropism for the placenta and the pregnant uterus and has the ability to invade and replicate within cells of the maternal-fetal unit, including trophoblasts and decidual cells. Placentitis is a common finding in infected pregnant animals. Several proinflammatory factors have been found to be increased in both the placenta of Brucella-infected animals and in trophoblasts or decidual cells infected in vitro. As normal pregnancies require an anti-inflammatory placental environment during most of the gestational period, Brucella-induced placentitis is thought to be associated with the obstetric complications of brucellosis. A few studies suggest that the blockade of proinflammatory factors may prevent abortion in these cases.

Turning chaotic sample group clusterization into organized ones by feature selection: Application on photodiagnosis of Brucella abortus serological test

Bovine brucellosis diagnosis is a major problem to be solved; the disease has a tremendous economic impact with significant losses in meat and dairy products, besides the fact that it can be transmitted to humans. The sanitary measures instituted in Brazil are based on disease control through diagnosis, animal sacrifice, and vaccination. Although the currently available diagnostic tests show suitable quality parameters, they are time-consuming, and the incidence of false-positive and/or false-negative results is still observed, hindering effective disease control. The development of a low-cost, fast, and accurate brucellosis diagnosis test remains a need for proper sanitary measures at a large-scale analysis. In this context, spectroscopy techniques associated with machine learning tools have shown great potential for use in diagnostic tests. In this study, bovine blood serum was investigated by UV-vis spectroscopy and machine learning algorithms to build a prediction model for Brucella abortus diagnosis. Here we first pre-treated the UV raw data by using Standard Normal Deviate method to remove baseline deviation, then apply principal component analysis - a clustering method - to observe the group formation tendency; the first results showed no clustering tendency with a messy sample score distribution, then we properly select the main principal components to improve clusterization. Finally, by using machine learning algorithms (SVM and KNN), the predicting models achieved a 92.5% overall accuracy. The present methodology provides a test result in an average time of 5 min, while the standard diagnosis, with the screening and confirmatory tests, can take up to 48 h. The present result demonstrates the method's viability for diagnosing bovine brucellosis, which can significantly contribute to disease control programs in Brazil and other countries.

Brucella abortus Strain RB51 Administered to Prepubescent Water Buffaloes, from Vaccination to Lactation: Kinetics of Antibody Response and Vaccine Safety

Brucella RB51 is a live modified vaccine. Its use in water buffalo has been proposed using a vaccination protocol different to that used for cattle, but knowledge of the long-term effects of RB51 vaccination in this species remains incomplete. The aim of the study was to evaluate the safety and kinetics of antibody responses in water buffaloes vaccinated according to the protocol described for the bovine species in the WOAH Manual, modified with the use of a triple dose. Water buffaloes were vaccinated with the vaccine RB51. A booster vaccination was administered at 12 months of age. When turning 23-25 months old, female animals were induced to pregnancy. RB51-specific antibodies were detected and quantified using a CFT based on the RB51 antigen. Vaccinated animals showed a positive serological reaction following each vaccine injection, but titers and the duration of the antibody differed among animals. For 36 weeks after booster vaccination, the comparison of CFT values between vaccinated and control groups remained constantly significant. Afterwards, antibody titers decreased. No relevant changes in antibody response were recorded during pregnancy or lactation. In conclusion, results indicated that the vaccination schedule applied is safe and allows for vaccinated and unvaccinated controls to be discriminated between for up to 8 months after booster vaccination.

Seroprevalence, and molecular detection of Brucella abortus in cattle tissues from an abattoir in Namibia

Brucellosis is a worldwide zoonosis that is endemic in Namibia. This study estimated seroprevalence of brucellosis, and determined the presence of Brucella infection in slaughtered cattle using the genus-specific 16-23S rRNA interspacer PCR (ITS-PCR), and the species-specific AMOS-PCR. Between December 2018 and May 2019, sera (n = 304), pooled lymph nodes (n = 304), and individual spleen (n = 304) were collected from slaughtered cattle from 52 farms. Sera were tested for anti-Brucella antibodies using the Rose Bengal test (RBT), and the complement fixation test (CFT). Seroprevalence was 2.3% (7/304) (RBT) and 1.6% (5/304) (CFT). Prevalence of positive herds was 9.6% (5/52). Lymph node (n = 200) and spleen (n = 200) samples from seronegative cattle tested negative for Brucella spp. DNA on ITS-PCR, but Brucella spp. DNA was detected in lymph nodes (85.7%, 6/7) and spleen (85.7%, 6/7) from RBT positive cattle. ITS-PCR confirmed isolates from lymph node (51.4%, 4/7) and spleen (85.7%, 6/7) as Brucella spp.; while AMOS-PCR and Brucella abortus species specific (BaSS) PCR confirmed the isolates as Brucella abortus, and field strains, respectively. Provision of adequate protective gear, and the promotion of brucellosis awareness among abattoir workers is recommended to prevent zoonotic infection.

Cell and Tissue Tropism of Brucella spp

Brucella spp. are facultatively intracellular bacteria that can infect, survive, and multiply in various host cell types in vivo and/or in vitro. The genus Brucella has markedly expanded in recent years with the identification of novel species and hosts, which has revealed additional information about the cell and tissue tropism of these pathogens. Classically, Brucella spp. are considered to have tropism for organs that contain large populations of phagocytes such as lymph nodes, spleen, and liver, as well as for organs of the genital system, including the uterus, epididymis, testis, and placenta. However, experimental infections of several different cultured cell types indicate that Brucella may actually have a broader cell tropism than previously thought. Indeed, recent studies indicate that certain Brucella species in particular hosts may display a pantropic distribution in vivo. This review discusses the available knowledge on cell and tissue tropism of Brucella spp. in natural infections of various host species, as well as in experimental animal models and cultured cells.

Histopathologic and immunohistochemical findings in the placentas and fetuses of domestic swine naturally infected with Brucella suis biovar 2

Porcine brucellosis, which is caused by Brucella suis biovar (bv) 2, is a re-emerging disease that causes reproductive problems in pigs in Europe. The pathogenesis and lesions of B. suis intrauterine infection are poorly characterized; characterization could facilitate the diagnosis and investigation of porcine brucellosis. We collected samples of placentas and fetuses for histologic and microbiologic studies during an outbreak of abortions on a pig-breeding farm in Spain. Brucella was cultured from the vaginal swabs obtained from sows that had aborted, some placentas, and fetal tissues (spleen, liver, lung, gastric content); molecular testing confirmed B. suis bv 2 infection. Histologically, there was necrotizing and hemorrhagic placentitis; suppurative hepatitis; lymphoid depletion and sinusoidal histiocytosis in the spleen, lymph nodes, and thymus; and bronchointerstitial pneumonia. Hemorrhages were observed in the umbilical cord, heart, kidneys, and brain. We detected Brucella by immunohistochemistry (IHC) in all of the placentas and fetal organs studied, specifically in the trophoblasts of the chorionic epithelium, in the cytoplasm of macrophages in the chorionic stroma, and extracellularly in necrotic debris. Furthermore, we assessed the lymphocyte population in the placentas through the use of IHC (anti-CD3, anti-Pax5 antibodies), revealing that the lymphocytic response was composed of T cells but not B cells.

Equine brucellosis: current understanding and challenges

Brucellosis in equines, including horses, donkeys, and mules, is characterized by abscesses in tendons, bursae, and joints. Reproductive disorders, which are common in other animals, are rare in both males and females. Joint breeding of horses, cattle, and pigs was found as the main risk factor for equine brucellosis, with the transmission from equines to cattle or among equines possible, although unlikely. Hence, evaluation of the disease in equines can be considered an indirect indicator of the effectiveness of brucellosis control measures employed for other domestic species. Generally, the disease in equines reflects disease status in the sympatric domestic species, mainly cattle. It is important to note that in equines, the disease has no validated diagnostic test, which limits the interpretation of available data. Finally, it is important to mention that equines also represent significant Brucella spp. infection sources for humans. Considering the zoonotic aspect of brucellosis, the significant losses due to infection, and the representativeness of horses, mules, and donkeys in the society, as well as the continuous efforts to control and eradicate the disease in livestock, in this review, we covered the various aspects of brucellosis in equines and compile the sparse and diffuse information on the subject.

Original and introduced lineages co-driving the persistence of Brucella abortus circulating in West Africa

Introduction

Brucellosis, a serious public health issue affecting animals and humans, is neglected in West Africa (WA).

Methods

In the present study, bio-typing, multi-locus sequence typing (MLST), multiple-locus variable-number tandem repeat analysis (MLVA), and whole genome sequencing single-nucleotide polymorphism (WGS-SNP) analysis were used to characterize the Brucella abortus (B. abortus) strains from WA.

Results

All of the 309 strains analyzed in this study were extracted and downloaded from the international MLVA bank and were from 10 hosts (cattle, humans, ovine, buffalo, dromedaries, horse, sheep, zebu, dog, and cat) distributed in 17 countries in WA. Based on the bio-typing, three biovars, dominated by B. abortus bv.3, were observed and reported across seven decades (1958–2019). With MLST, 129 B. abortus strains from the present study were sorted into 14 STs, with ST34 as the predicted founder. These 14 STs clustered into the global MLST data into three clone complexes (C I–C III) with the majority of strains clustering in C I, while C II forms an independent branch, and C III harbors three STs shared by different continents. These data revealed that most cases were caused by strains from native lineages. According to the MLVA-11 comparison, 309 strains were divided into 22 MLVA-11 genotypes, 15 of which were unique to WA and the remaining seven had a global distribution. MLVA-16 analysis showed that there were no epidemiological links among these strains. Based on the MLVA data, B. abortus strains from WA have high genetic diversity, and predominated genotypes were descended from a native lineage. While the MLVA-16 globally highlights that the dominant native and few introduced lineages (from Brazil, the USA, South Korea, Argentina, India, Italy, Portugal, the UK, Costa Rica, and China) co-driving the B. abortus ongoing prevalence in WA. The high-resolution SNP analysis implied the existence of introduced B. abortus lineages, which may be reasonably explained by the movement and trade of dominant hosts (cattle) and/or their products.

Discussion

Our results indicated that B. abortus strains in WA consist of native and introduced strains that necessitate control such as vaccination, testing, slaughtering, and movement control by the relevant country authorities to reduce brucellosis in livestock.

Evaluation of the goat cellular immune response to rBtuB-Hia-FlgK peptides from Brucella melitensis

Brucellosis is a zoonosis caused by Brucella; B. melitensis is the most prevalent species in goats and humans. Previously, three B. melitensis peptides, rBtuB-Hia-FlgK showed antigen-specific immune responses in rodent models. The goal of this study was to evaluate the goat Th1/Th2 immune response to B. melitensis peptides. Twenty-eight animals were separated into four groups and were immunized with the rBtuB-Hia-FlgK peptides cocktail, adjuvant, PBS and Rev-1 vaccine, respectively. Peripheral blood samples were collected on days 0, 15, and 80 post-inoculation. The CD4+ and CD8+ T cells proliferation, and cytokine production of the Th-1 (IL-2, IL-12, TNF-α, and IFN-γ) and Th-2 profiles (IL-4, IL-5, and IL-10) were evaluated. An increase of CD4+/CD8+ at 15 days post-vaccination was observed and continued until the 80th. In addition, the IFN-γ, TNF-α, and IL-2 mRNA expression were typically induced by the 15th day, but only IFN-γ levels were observed at day 80 post-immunization. Brucella pathogenesis is distinguished by the presence of a large amount of Th-1 cytokines. Although a reduced amount of IFN-γ in the culture supernatant was accurately detected compared with Rev-1 after 15 days, it could be influenced by the sampling schedule, as a higher cytokine production might be induced as early as the first-week post-vaccination. The results indicate that rBtuB-Hia-FlgK induced an immune response similar to the Rev-1 vaccine. The possible use of inert molecules with the unique ability to typically induce cellular response similar to attenuated vaccine represents an attractive option that should not be ruled out.

Differentially expressed long noncoding RNAs in RAW264.7 macrophages during Brucella infection and functional analysis on the bacterial intracellular replication

Long noncoding RNAs (lncRNAs) are a group of functional RNA molecules without protein-coding potential and play vital roles in majority of biological processes. To date, the expression profiles of lncRNAs and their influence on Brucella replication in RAW264.7 cells are poorly understood. In this study, we performed high-throughput transcriptome analysis to investigate the differentially expressed lncRNAs associated with Brucella abortus S2308 infection. Of these, 8, 6, 130 and 94 cellular lncRNAs were differentially expressed at 4, 8, 24 and 48 h post-infection, respectively. Moreover, 1918 protein-coding genes are predicted as potential cis target genes of differentially expressed lncRNAs by searching protein-coding genes located at upstream and downstream of lncRNA loci on the chromosome DNA of Mus musculus. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses indicated that majority of lncRNA target genes were associated with B. abortus infection. Fourteen lncRNAs from transcriptome data were selected for qRT-PCR verification, confirming 13 were differentially expressed. Animal experiments revealed three were differentially expressed in vivo by qRT-PCR analysis. Furthermore, knockdown of LNC_000428 by CRISPR/dCas9 inhibition or Locked Nucleic Acids transfection downregulated Tnfrsf8 expression at mRNA level and increased Brucella intracellular replication. Thus, we provide a novel evidence that lncRNAs induced by Brucella-infection function on Brucella intracellular replication.

Inflammatory Mechanism of Brucella Infection in Placental Trophoblast Cells

Brucellosis is a severe zoonotic infectious disease caused by the infection of the Brucella, which is widespread and causes considerable economic losses in underdeveloped areas. Brucella is a facultative intracellular bacteria whose main target cells for infection are macrophages, placental trophoblast cells and dendritic cells. The main clinical signs of Brucella infection in livestock are reproductive disorders and abortion. At present, the pathogenesis of placentitis or abortion caused by Brucella in livestock is not fully understood, and further research on the effect of Brucella on placental development is still necessary. This review will mainly introduce the research progress of Brucella infection of placental trophoblast cells as well as the inflammatory response caused by it, explaining the molecular regulation mechanism of Brucella leading to reproductive system disorders and abortion, and also to provide the scientific basis for revealing the pathogenesis and infection mechanism of Brucella.

A case study investigating the effects of emergency vaccination with Brucella abortus A19 vaccine on a dairy farm undergoing an abortion outbreak in China

Brucellosis is an important zoonosis that results in substantial economic losses to the livestock industry through abortions and reduced milk yield. This study investigated an abortion outbreak in a dairy herd and then explored the effects of emergency vaccination with Brucella abortus A19 vaccine on the incidence of abortion and milk yield. A full dose of vaccine (6 × 1010—12 × 1010 colony forming units, CFU) was administered subcutaneously to calves and non-pregnant heifers, and a reduced dose (6 × 108—12 × 108 CFU) to adult cows and pregnant replacement heifers. Rose Bengal Test was used to screen Brucella infection status and then positive samples were tested with a C-ELISA. Animals that tested positive for both tests were considered positive to Brucella spp. The animal-level seroprevalence of brucellosis was 23.1% (95% CI: 17.0, 30.2), and the attributable fraction of abortions in seropositive animals was 89.1% (95% CI: 64.3, 96.7). The odds of seropositivity were significantly higher in cows that aborted compared to cows that calved normally (OR = 21.4, 95% CI: 4.4, 168.4). Cows in sheds A2 and C1 were 10.2 (95% CI: 1.4, 128.0) and 17.0 (95% CI: 2.8, 190.3) times more likely to be seropositive than cows in shed B1. Antibodies were not detectable in most heifers 12 months post-vaccination. The effectiveness of the vaccine in preventing abortions was estimated to be 56.8% (95% CI: 15.8, 77.8) for the entire herd, but increased to 86.7% (95% CI: 4.4, 98.1) when only primiparous heifers were considered. Furthermore, a significant increase in the average herd 305-day milk yield one-year after vaccination was also observed relative to that in the previous three years. It is concluded that emergency vaccination of a dairy herd undergoing an abortion outbreak with the A19 vaccine effectively reduced the incidence of abortion and indirectly increased milk yield one-year after vaccination.

Bayesian Evaluation of Three Serological Tests for Diagnosis of Brucella infections in Dromedary Camels Using Latent Class Models

Brucellosis is a zoonotic disease with significant economic and public health impacts. The disease has been found in ruminants, including camels, but clinical diagnosis of camel brucellosis is difficult due to the lack of clinical signs. Thus, this study aimed to estimate the sensitivity (Se) and specificity (Sp) of the Buffered Plate Antigen Test (BPAT), Rose Bengal Test (RBT), and indirect ELISA (i-ELISA) for the diagnosis of Brucella infection in dromedary camels imported from Sudan to Egypt. The secondary objective of the study was to calculate the animal-level true prevalence of Brucella infection in imported camels. A cross-sectional study was carried out on 921 apparently healthy camels randomly selected from those imported from Sudan and kept in the quarantine stations in the Shalateen area of the Red Sea Governorate, Egypt, between June 2018 and January 2019. Serum samples were collected and analyzed using BPAT, RBT, and i-ELISA. The posterior estimates [medians and 95% Bayesian probability intervals (95% BPI)] for Se and Sp of the three serological tests were obtained using Bayesian latent class models (BLCMs). The BLCM was fitted with the assumption that the BPAT and RBT tests were conditionally dependent on the true brucellosis status of camels. All tests had comparable and high Se (>86%) and Sp (>98%). The animal-level true prevalence of Brucella infection in imported camels was 8.6% (95% BPI: 6.8 - 10.7). Based on these findings, the three assays could be used for the initial screening of Brucella infection in camels. However, the BPAT and RBT are more suitable for use in camel brucellosis control and eradication program in Egypt because of their low unit cost and fast turnaround time compared to the i-ELISA. In addition, BPAT and RBT could be performed in the field where in-vivo tests are rarely used due to logistic and management constraints.

Prevalence of brucellosis in livestock of African and Asian continents: A systematic review and meta-analysis

Brucellosis is a highly contagious bacterial disease that mainly affects ruminants, but it may affect equines, canines, and felines. The disease is of utmost significance from an economic standpoint in countries where there is no national brucellosis prevention and eradication policy in operation. A systematic review was done to estimate disease burden, incidences, prevalence, and geographical distribution critical in planning appropriate intervention strategies for the control and prevention of Brucellosis. Research articles that were published during the period 2000–2020 were considered for this study after reinforced scrutiny by two independent authors. Meta-regression was used to examine heterogeneity, and subgroup and sensitivity analyses were used to calculate residual heterogeneity and the pooled prevalence of Brucellosis in livestock. Confounders such as geography, a diagnostic test, and species had the greatest R2 values of 17.8, 8.8, and 2.3%, respectively, indicating the presence of heterogeneity and necessitating more research into sensitivity and subgroup analysis. The combined pooled prevalence of brucellosis in both Asia and African countries was 8% when compared to 12% in the Indian livestock population. The findings of our systematic review and meta-analysis indicate that brucellosis continues to be an important animal and public health concern in developing countries of Asia and Africa, as evidenced by the prevalence rate of brucellosis in these regions. Our findings suggested that well-planned epidemiological surveillance studies in different geographic settings are needed to generate reliable data on disease burden including the economic loss in Asian and African countries.

The Flagellar Transcriptional Regulator FtcR Controls Brucella melitensis 16M Biofilm Formation via a betI-Mediated Pathway in Response to Hyperosmotic Stress

The expression of flagellar proteins in Brucella species likely evolved through genetic transference from other microorganisms, and contributed to virulence, adaptability, and biofilm formation. Despite significant progress in defining the molecular mechanisms behind flagellar gene expression, the genetic program controlling biofilm formation remains unclear. The flagellar transcriptional factor (FtcR) is a master regulator of the flagellar system’s expression, and is critical for B. melitensis 16M’s flagellar biogenesis and virulence. Here, we demonstrate that FtcR mediates biofilm formation under hyperosmotic stress. Chromatin immunoprecipitation with next-generation sequencing for FtcR and RNA sequencing of ftcR-mutant and wild-type strains revealed a core set of FtcR target genes. We identified a novel FtcR-binding site in the promoter region of the osmotic-stress-response regulator gene betI, which is important for the survival of B. melitensis 16M under hyperosmotic stress. Strikingly, this site autoregulates its expression to benefit biofilm bacteria’s survival under hyperosmotic stress. Moreover, biofilm reduction in ftcR mutants is independent of the flagellar target gene fliF. Collectively, our study provides new insights into the extent and functionality of flagellar-related transcriptional networks in biofilm formation, and presents phenotypic and evolutionary adaptations that alter the regulation of B. melitensis 16M to confer increased tolerance to hyperosmotic stress.

Animal and human brucellosis in Algeria: a review

Tawla n Malṭa d aṭṭan ittenṭaḍen ɣer umdan i d-xeddment tbaktiriyin n tewsit Brucella spp. D aṭṭan amaḍlan u tella deg tmura n wagrakal am Lezzayer anda mazal txeddem axessar deg lmal. Ad d-nawi dagi tasɣunt tamatut ɣef tawla n Malṭa di Lezzayer, anda i tt-id-ufan yakan ɣer umdan seg 1895 u deg wass-nni mazal-itt d ugur ameqqran i yimeẓla n tdawsa. Tella tezqaft deg tejṛutin n yimdanen deg temnaḍt ɣer tayeḍ, tamnaḍt yennul ugar d tamnaḍt uzawaɣ i yesɛan weḥd-s aktamur alemmas (tajṛut/100 000 imezdaɣ) n 65.87 teḍfer-itt-id s 9.89 deg temnaḍt Agafa-Asamar ɣef wakken i d-iwekked uɣlif n tdawsa. Aktamur n tejṛutin n tawla n Malṭa n yizgaren iɛedda s uḍfar deg 5% ar 0,76% deg tlemmast n yiseggasen n 90 d 2014 s usileɣ imfeccec anda seld ṣa yiseggasen n wahil n takza d usnefren akked ucraḍ s tgezzayt REV-1 i d-ihegga uɣlif n tdawsa mazal yegguma ad isenger aṭṭan-agi. Ilaq daɣen ad negzu dakken anerni n umḍan n tejṛutin timaynutin n yimdanen i ittujerden kifkif-it akked tejṛutin ɣer tɣeṭṭen i yellan d aɛwin n temsalmit meqqren i umdan di Lezzayer.

Antibiogram Screening and Detection of Virulence-Associated Genes in Brucella Species Acquired from Cattle in South Africa's Eastern Cape Province

Brucellosis is a widespread zoonotic illness, and it poses serious public health and economic risks. The purpose of this investigation is to look at the antimicrobial susceptibility of unpasteurized milk, blood, and lymph node specimens from cattle, goats, and sheep, as well as to identify virulence-associated genes. In this investigation, a total of 123 isolates were examined. The activity of 15 antimicrobials against Brucella pathogens were assessed using the Kirby−Bauer disk diffusion technique. Nine virulence factors were detected with polymerase chain reaction analysis. Five antibiotics were 100% effective against Brucella isolates. A high level of resistance (100%) was documented with streptomycin, penicillin, and seven more antibiotics. Doxycycline resistance was found in 12% of goat isolates, and tetracycline resistance was found in 21% and 44% of goat and sheep isolates, respectively. Multiple antibiotic resistance (MAR) index >0.2 was found in 38.2% (47/123) of Brucella isolates. VecC and BetB, two B. abortus genes, were confirmed to be comparable. The findings of this study suggests that Brucella spp. are reservoirs of antibiotic resistance in the Eastern Cape Province. As such, they represent a potential pool of antibiotic genes that might be transferred to other pathogens in the community, and thus continue to pose a healthcare hazard.

Use of a Participatory Method for Community-Based Brucellosis Control Design in Agro-Pastoral Areas in Tanzania

Brucellosis is widespread in both humans and livestock in many developing countries. The authors have performed a series of epidemiological studies on brucellosis in agro-pastoral areas in Tanzania since 2015, with the aim of the disease control. Previously, the potential of a community-based brucellosis control initiative, which mainly consisted of the sale of cattle with experience of abortion and vaccinating calves, was assessed as being effective and acceptable based on a quantitative approach. This study was conducted to investigate the feasibility of community-based brucellosis control program using participatory rural appraisals (PRAs) and key-informant interviews. Four PRAs were performed together with livestock farmers and livestock and medical officers in 2017. In the PRAs, qualitative information related to risky behaviors for human infection, human brucellosis symptoms, willingness to sell cattle with experience of abortion, and willingness to pay for calf vaccination were collected, and a holistic approach for a community-based disease control project was planned. All of the communities were willing to implement disease control measures. To avoid human infection, education, especially for children, was proposed to change risky behaviors. The findings of this study showed that community-based disease control measures are promising.

Bovine Brucellosis in Gauteng, South Africa: Seroprevalence amongst Cattle Handlers and Variables Associated with Seropositive Cattle Herds, 2014-2016

In South Africa, the prevalence of cattle handler exposure to Brucella on cattle farms is unknown and risk factors and cattle symptoms associated with infected cattle herds are unavailable. To address this gap, a case-control study of cattle herds was conducted in Gauteng province and farm workers and veterinary officials were tested for exposure to Brucella. Seroprevalence amongst farm workers exposed to case herds ranged from 4.0% (BrucellaCapt®) to 16.7% (IgG ELISA®), compared to those exposed to control herds, where seroprevalence ranged from 1.9% (BrucellaCapt®) to 5.7% (IgG ELISA®). Seroprevalence amongst veterinary officials was significantly greater compared to farm workers exposed to case herds for the outcome RBT+ IgM- IgG+ (OR = 11.1, 95% CI: 2.5-49.9, p = 0.002) and RBT- IgM- IgG+ (OR = 6.3, 95% CI: 2.3-17.3, p < 0.001). Risk factors associated with being an infected herd were: being a government-sponsored farm vs. private farm (OR 4.0; 95% CI: 1.4-11.3; p = 0.009), beef vs. dairy herd (OR 7.9; 95% CI: 1.4-44.9; p = 0.020), open vs. closed herd (OR 3.3; 95% CI: 1.1-10.4; p = 0.038) and the presence of antelope on the farm (OR 29.4; 95% CI: 4.0-218.2; p = 0.001). Abortions (OR = 5.1; 95% CI: 2.0-13.3; p < 0.001), weak calves in the herd (OR = 8.0; 95% CI: 2.6-24.4; p < 0.001), reduction in number of calves born (OR = 9.0; 95% CI: 2.1-43.6; p < 0.001), reduction in conception rate (OR = 3.9; 95% CI: 0.8-18.3; p = 0.046), hygromas in cattle (p = 0.011) and farmers reporting brucellosis-like symptoms in their farm workers or in him/herself (OR = 3.4; 95% CI: 1.3-8.7; p = 0.006) were more likely to be associated with Brucella infected herds than control herds. This evidence can be used in strategic planning to protect both human and herd health.

Effect of co-positivity for brucellosis and tuberculosis on milk yield and fertility of Holstein cows

This study aimed to determine whether cows detected as tuberculosis (bTB) reactors and seropositive to brucellosis (bBR), as well as co-positive to bBR and bTB (bBR-bTB) and with a complete lactation before slaughter, were associated with reduced milk production and fertility. A total of 8068 productive and reproductive records of high-yielding Holstein cows from a single large dairy herd with a high prevalence of bTB and bBR were collected from 2012 to 2015. Lactation derived either from calving (n = 6019) or hormonally induced lactation (n = 2049), and all cows received growth hormone throughout lactation. For cows not induced into lactation, pregnancy rate to first service for healthy cows (C; 26.6%) was higher (P < 0.01) than bBR (15.2%), bTB (15.8%), and bBR-bTB (1.3%) cows. For induced cows, pregnancy rate to first service did not differ significantly among C, bBR, and bTB (14.5-17.3%) cows, but the percentage success of first service was extremely low (1.3%; P < 0.01) in bBR-bTB cows. Services per pregnancy (only pregnant cows) were lowest for C (3.3 ± 2.9; P < 0.01) and highest (6.4 ± 3.4) for bBR-bTB non-induced cows. This variable was lowest for C (2.9 ± 2.5; P < 0.01) and highest for bBR-bTB non-induced cows (6.3 ± 3.1). Pregnancy rate to all services did not differed for C (79.5%), bBR (76.7%), and bTB (75.9%) but was lower (58.9%; P < 0.01) for bBR-bTB non-induced cows. For induced cows this variable was highest for bBR (53.3%) and lowest for bBR-bTB (34.1%; P < 0.01) non-induced cows. 305-d milk production was increased by 4%, and total milk yield by 7% in TB-positive cows compared to that of the negative cows non-induced hormonally into lactation. This study showed the negative impact of the co-positivity for bTB and bBR on the reproductive efficiency of Holstein cows, although positive bTB and bBR tests enhanced milk yield.

Seroprevalence and risk factors for bovine brucellosis in the state of Paraná, Brazil: an analysis after 18 years of ongoing control measures

Seroprevalence and risk factors of bovine brucellosis (Brucella abortus) in herds and cattle were estimated by a cross-sectional study in the state of Paraná, Brazil. The state was divided into seven regions and a random, two-stage sampling was performed on properties and cattle from each region between 2018 and 2019. Serum samples were collected from 11,592 cows over 24 months from 1,757 properties and a questionnaire was applied to identify potential risk factors. As recommended by the National Program for the Control and Eradication of Animal Brucellosis and Tuberculosis (PNCEBT), serological testing for the detection of anti-Brucella antibodies included the buffered plate agglutination test (screening test) and the fluorescence polarization assay (confirmatory test). The seroprevalence of bovine brucellosis on properties and in cattle was 4.87% (95% confidence interval [CI]: 3.98-5.93%) and 2.24% (95% CI: 1.47-3.41%), respectively. Multiple logistic regression analysis identified larger herd size and failure to test for brucellosis as risk factors for the presence of anti-B. abortus antibodies. These results demonstrate no change in the prevalence when comparing initial studies conducted in 2002. Given our findings, it is recommended that policies for brucellosis control include a widespread vaccination program for higher prevalence areas and eradication approach to lower prevalence areas. All steps related to correct immunization of the herds should be verified and improved by training and education. Health education action must be carried out informing farmers about the risks of introducing animals not tested for brucellosis into their herds and the benefits of testing their herds regularly.

Are infectious reproductive pathogens of large ruminants a threat to improving food security? An investigation from Cambodia

In Cambodia, information on common pathogens causing reproductive losses in cattle and buffalo are lacking, despite there being a need to address livestock health to enhance food security. We analysed stored buffalo (n = 29) and cattle (n = 471) serum samples collected in 2016 using commercially available enzyme-linked immunosorbent assay kits. Antibodies to Neospora caninum, bovine viral diarrhoea virus (BVDV), Leptospira interrogans serovar Hardjo and Brucella abortus were detected in buffalo samples at 79.3% (95% CI 64.6-94.0), 3.4% (95% CI 0-10.0), 0% and 0%, respectively, and in cattle at 4.2% (95% CI 2.4-6.0), 6.4% (95% CI 4.2-8.6), 8.1% (95% CI 5.6-10.6) and 0%, respectively. The high N. caninum seroprevalence in buffalo was associated with increasing age, with buffalo having a 13.1% chance of being seropositive at birth, increasing to 99.4% by age 7 (p = 0.045). This suggests a predominance of horizontal transmission, possibly from exposure to faeces from free-roaming village dogs. Cattle L. interrogans serovar Hardjo seroprevalence was highest in Tbong Khmum province (20.4%) compared to other provinces (p < 0.001), and may be compromising bovine fertility and creating a zoonotic risk for smallholders who may contract leptospirosis from farm work. These high infection rates prompt further research to determine: to what extent these pathogens are linked to the low reproductive efficiency observed in large ruminants in Cambodia, the risk factors to pathogen exposure and appropriate strategies to reduce these risks. Low BVDV and B. abortus exposure is an important observation. Increasing large ruminant livestock trade into the country will require improved biosecurity and disease surveillance to prevent their emergence. An enhanced understanding of the status of infectious reproductive livestock pathogens in Cambodia can assist development projects to make evidence-based strategies to enhance cattle and buffalo health and improve food security.

Protective efficacy of attenuated Salmonella Typhimurium strain expressing BLS, Omp19, PrpA, or SOD of Brucella abortus in goats

Background

Attenuated Salmonella strain can be used as a vector to transport immunogens to the host antigen-binding sites.

Objectives

The study aimed to determine the protective efficacy of attenuated Salmonella strain expressing highly conserved Brucella immunogens in goats.

Methods

Goats were vaccinated with Salmonella vector expressing individually lipoprotein outer-membrane protein 19 (Omp19), Brucella lumazine synthase (BLS), proline racemase subunit A (PrpA), Cu/Zn superoxide dismutase (SOD) at 5 × 10⁹ CFU/mL and challenge of all groups was done at 6 weeks after vaccination.

Results

Among these vaccines inoculated at 5 × 10⁹ CFU/mL in 1 mL, Omp19 or SOD showed significantly higher serum immunoglobulin G titers at (2, 4, and 6) weeks post-vaccination, compared to the vector control. Interferon-γ production in response to individual antigens was significantly higher in SOD, Omp19, PrpA, and BLS individual groups, compared to that in the vector control (all p < 0.05). Brucella colonization rate at 8 weeks post-challenge showed that most vaccine-treated groups exhibited significantly increased protection by demonstrating reduced numbers of Brucella in tissues collected from vaccinated groups. Real-time polymerase chain reaction revealed that Brucella antigen expression levels were reduced in the spleen, kidney, and parotid lymph node of vaccinated goats, compared to the non-vaccinated goats. Besides, treatment with vaccine expressing individual antigens ameliorated brucellosis-related histopathological lesions.

Conclusions

These results delineated that BLS, Omp19, PrpA, and SOD proteins achieved a definite level of protection, indicating that Salmonella Typhimurium successfully delivered Brucella antigens, and that individual vaccines could differentially elicit an antigen-specific immune response.

Efficacy of Brucella abortus S19 and RB51 vaccine strains: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to recalculate the efficacy of Brucella abortus S19 and RB51 vaccine strains and discuss the main variables associated with controlled trials to evaluate bovine brucellosis vaccine efficacy (VE). The most commonly used vaccine strain was S19, at a dose of 10¹⁰ colony forming units (CFU), followed by RB51 at 10¹⁰ CFU. The most commonly used challenge strain was B. abortus 2308, at a dose of 10⁷ CFU, by the intraconjunctival route. Regarding the meta-analysis, trials were grouped according to the vaccine strain and dose to recalculate protection against abortion (four groups) or infection (five groups) using pooled risk ratio (RR) and VE. Regarding protection against abortion (n = 15 trials), the S19 vaccine at 10⁹ CFU exhibited the highest protection rate (RR = 0.25, 95% confidence interval (CI) : 0.12-0.52; VE = 75.09%, 95% CI: 48.08-88.05), followed by RB51 at 10¹⁰ CFU (RR = 0.31, 95% CI: 0.16-0.61; VE = 69.25%, 95% CI: 39.48-84.38). Regarding protection against infection (n = 23 trials), only two subgroups exhibited significant protection: S19 at 10⁹ CFU (RR = 0.28, 95% CI: 0.14-0.55; VE = 72.03%, 95% CI: 57.70- 81.50) and RB51 at 10¹⁰ CFU (RR = 0.43, 95% CI: 0.22-0.84; VE = 57.05%, 95% CI: 30.90-73.30). In conclusion, our results suggest that a dose of 10⁹ CFU for S19 and 10¹⁰ CFU for RB51 are the most suitable for the prevention of abortion and infection caused by B. abortus.

The epidemiology of bacterial zoonoses in pastoral and dairy cattle in Cameroon, Central Africa

Previous work identified that bacterial zoonoses (Brucella species, Coxiella burnetii and Leptospira hardjo) were present in Cameroonian pastoral cattle. To assess the characteristics of this zoonotic risk, we analyse seroprevalence of each pathogen and the associated management, herd and environmental factors in Cameroonian pastoral and dairy cattle. Cross-sectional samples included pastoralist herds in the Northwest Region (NWR n = 750) and Vina Division (VD n = 748) and small holder dairy herds in the NWR (n = 60). Exposure to Brucella spp., C. burnetii and L. hardjo were screened for using commercial ELISAs and population adjusted estimates made. In addition, individual, herd and ecological metadata were collected and used to identify risk factors associated with animal-level seropositivity. In the pastoral cattle, seroprevalence to Brucella spp. was relatively low but was higher in the NWR (4.2%, CI: 2.5%-7.0%) than the VD (1.1%: CI 0.5%-2.4%), while L. hardjo seroprevalence was much higher though similar in the NWR (30.7%, CI 26.3%-35.5%) and VD (35.9%, CI 31.3%-40.7%). No differences were noted in C. burnetii seroprevalence between the two study sites (NWR: 14.6%, CI 11.8%-18.0%. VD: 12.4%, 9.6%-15.9%). Compared to pastoral, dairy cattle had lower seroprevalences for L. hardjo (1.7%, CI: 0.0%-4.9%), C. burnetii (0.0%, CI 0.0%-6.0%) but similar for Brucella spp. (5.0%, CI 0.0%-10.6%). Increased odds of Brucella spp. seropositivity were associated with owning sheep or rearing sheep and fencing cattle in at night. Adult cattle had increased odds of being seropositive for both C. burnetii and L. hardjo. Additionally, exposure to C. burnetii was associated with local ecological conditions and L. hardjo was negatively associated with cattle undertaking transhumance. This work highlights that exposure to these 3 important production diseases and occupational zoonoses are widespread in Cameroonian cattle. Further work is required to understand transmission dynamics between humans and livestock to inform implementation of effective control measures.

Bovine brucellosis - a comprehensive review

Brucellosis is a zoonotic disease of great animal welfare and economic implications worldwide known since ancient times. The emergence of brucellosis in new areas as well as transmission of brucellosis from wild and domestic animals is of great significance in terms of new epidemiological dimensions. Brucellosis poses a major public health threat by the consumption of non-pasteurized milk and milk products produced by unhygienic dairy farms in endemic areas. Regular and meticulous surveillance is essentially required to determine the true picture of brucellosis especially in areas with continuous high prevalence. Additionally, international migration of humans, animals and trade of animal products has created a challenge for disease spread and diagnosis in non-endemic areas. Isolation and identification remain the gold standard test, which requires expertise. The advancement in diagnostic strategies coupled with screening of newly introduced animals is warranted to control the disease. Of note, the diagnostic value of miRNAs for appropriate detection of B. abortus infection has been shown. The most widely used vaccine strains to protect against Brucella infection and related abortions in cattle are strain 19 and RB51. Moreover, it is very important to note that no vaccine, which is highly protective, safe and effective is available either for bovines or human beings. Research results encourage the use of bacteriophage lysates in treatment of bovine brucellosis. One Health approach can aid in control of this disease, both in animals and man.

In Vitro and In Vivo IFN-γ and IL-10 Measurement in Experimental Brucella abortus Biotype 1 Infection in Sprague-Dawley Rats

The immune response to Brucella abortus mainly depends on antigen-specific T cell activation, CD4⁺ and CD8⁺ T cells, and Brucella-specific humoral response. Protective immune response against Brucella infection has not been performed in the Sprague-Dawley (SD) rat model. We measured bacterial kinetics in addition to in vivo and in vitro interferon gamma (IFN-γ) and interleukin-10 (IL-10) production against crude Brucella protein in the SD rats at different days of postinfection with B. abortus biotype 1 by indirect enzyme-linked immunosorbent assay. Forty SD rats were inoculated intraperitoneally with 0.1 mL sterile injectable pyrogen-free solution containing 1 × 10¹⁰ colony-forming units/mL of B. abortus biotype 1 obtained from cattle in Korea. Four rats were used as uninfected control. Serum IFN-γ level at 3 and 7 days postinfection were significantly higher (p > 0.001) compared with the IL-10 level. On the contrary, serum IL-10 levels were observed significantly higher at 21 and 28 days postinfection compared with the serum IFN-γ levels (p < 0.001). The production of IFN-γ by spleen cells was significantly higher at 7 and 14 days postinfection compared with IL-10 (p < 0.001). On the contrary, IL-10 productions were found to be significantly higher at 21, 28, 35, and 42 days postinfection compared with IFN-γ (p < 0.001). The presence of B. abortus in blood was marked till 5 weeks of infection, throughout the experiment in case of spleen, and no bacteria were isolated from the kidney and liver at 6 weeks postinfection. The in vivo and in vitro IFN-γ and IL-10 measurement in our study reported that B. abortus infection in rats primarily educe T helper (Th)1-dominant immune response in acute infection accompanied by Th2-dominant immune response in chronic infection.

Effects of vaccination against brucellosis and clostridia on the intake, performance, feeding behavior, blood parameters, and immune responses of dairy heifers calves

The aim of this study was to identify possible effects of different vaccination strategies (concomitantly or not) against brucellosis and clostridia on intake, performance, feeding behavior, blood parameters, and immune responses of dairy heifers calves. Fifty heifers calves were enrolled [38 Gyr (Zebu, Bos taurus indicus) and 12 5/8 Holstein × Gyr]. At 120 d of age, animals were randomly distributed among 3 groups: B (n = 18), vaccinated against brucellosis; C (n = 14), vaccinated against clostridia and CB (n = 18), vaccinated concomitantly for both. Rectal and thermographic temperatures were evaluated on days -1, 0, 1, 2, 3, 5, 7,10, 14, and 28 relatives to the vaccination day. Feed and water intake, body weight (BW), and feeding behavior were monitored daily by an electronic feeding system. Blood was sampled on days 0, 3, 7, 14, and 28, relative to the vaccination day for determination of glucose and β -hydroxybutyrate (BHBA) concentrations. Blood sampled on day 0 (prevaccination) and on days 28 and 42 were used to evaluate the immune response against Brucella abortus and clostridia. There was an increase in rectal temperature between the first and the third day postvaccination in the 3 groups. The thermography revealed an increase of local temperature for 7 d on groups B and CB. Group C had increased local temperature for a longer period, lasting for up to 14 d. Dry mater intake was reduced for groups B and CB, but no alteration was observed for group C. No alterations regarding initial BW, final BW, average daily weight gain, and feed efficiency were observed. No differences were observed for the 3 vaccination groups for blood parameters throughout the evaluation period. The concomitant vaccination against brucellosis and clostridia led to lower neutralizing antibody titers against epsilon toxin of Clostridium perfringens and botulinum toxin type C of C. botulinum (C > CB > B). When cellular proliferation assay and serological tests to B. abortus were evaluated, no differences were observed between groups B and CB. The present results indicate that the concomitant vaccination against brucellosis and clostridia has no relevant impact on the intake, performance, and feeding behavior of dairy calves. However, the concomitant vaccination of vaccines against these 2 pathogens impacts animal immunity against clostridial infections.

Canine Brucellosis: An Update

Canine brucellosis is an infectious and zoonotic disease caused by Brucella canis, which has been reported worldwide, and is a major public health concern due to close contact between dogs and humans. In dogs, canine brucellosis manifests with abortion outbreaks, reproductive failure, enlargement of lymph nodes, and occasionally affects the osteoarticular system, although the occurrence of asymptomatic infections in dogs are not uncommon. In humans, the disease is associated with a febrile syndrome, commonly with non-specific symptoms including splenomegaly, fatigue, and weakness. Infection of dogs occurs mostly by the oronasal route when in contact with contaminated tissues such as aborted fetuses, semen, urine, and vaginal secretions. In humans, contact with contaminated fluids from infected dogs is an important source of infection, and it is an occupational risk for veterinarians, breeders, laboratory workers, among other professionals who deal with infected animals or biological samples. The diagnosis in dogs is largely based on serologic methods. However, serologic diagnosis of canine brucellosis remains very challenging due to the low accuracy of available tests. Molecular diagnostic methods have been increasingly used in the past few years. Treatment of infected dogs is associated with a high frequency of relapse, and should be employed only in selected cases. Currently there are no commercially available vaccines for prevention of canine brucellosis. Therefore, development of novel and improved diagnostic methods as well as the development of efficacious and safe vaccination protocols are needed for an effective control of canine brucellosis and its associated zoonotic risk.

Dexamethasone-induced stress exacerbates shedding, tissue antigen distribution, and pathology of caprine Brucellosis

This study investigated dexamethasone-treatment, shedding routes, tissue antigen distribution, and pathology of caprine Brucellosis. Eighteen non-pregnant goats were randomly grouped into A, B, and C. Group A was administered dexamethasone for 7 days at 2 mg/kg before inoculating 0.5 mL B. melitensis at 10⁷ CFU ocularly while group B was inoculated 0.5 mL B. melitensis only, and C as control negative. Blood samples, ocular, nasal, and vaginal swabs were obtained for evaluation. Three goats were sacrificed from each group at days 21 and 42 post-inoculation (pi) and selected tissues collected for PCR, histopathology, and immunohistochemistry. Brucella melitensis was detected in the ocular swabs of group A significantly higher than group B. Shedding was prolonged in group A compared to B. The overall shedding was 22.2% in group A and 9.4% in group B. The uterus of both groups A and B revealed mild inflammation and microgranuloma, extensive necrotic lesions in lymph nodes. Liver showed multifocal necrosis predominantly in group A. Lesion scoring showed significantly higher scores in A compared to B. Strong immunostaining was observed in the liver, lungs, and spleen, predominantly at day 21 pi. This study demonstrated dexamethasone prolonged shedding, tissue antigen distribution, and pathology in dexamethasone-treated goats.

Seroprevalence of Bovine Brucellosis in Ethiopia: Systematic Review and Meta-Analysis

Brucellosis is an infectious and widespread zoonotic disease caused by bacteria of the genus Brucella and can induce considerable human suffering and huge economic losses in animals. Thus, the aim of this study was to conduct a systematic review and meta-analysis on the seroprevalence of bovine brucellosis in Ethiopia. PubMed, Science Direct, African Journals Online, and Google Scholar were used to search the articles. All references were screened and articles, which reported seroprevalence of bovine brucellosis in Ethiopia were included in the study. Meta-analysis using random-effects models was made to calculate the pooled seroprevalence of brucellosis. This review included 15 papers. The estimated pooled seroprevalence of brucellosis was found to be 3.0% (95% CI: 2.0, 4.0). The subgroup analysis showed that there was a statistically significant association between the disease and geographical location, setting, laboratory technique employed and study years. Also, there was some evidence of publication bias (Egger's test, p = 0.0003) on studies reporting the prevalence of brucellosis in Ethiopia. This review proves a high seroprevalence of brucellosis in the country and appropriate control strategies are recommended. Moreover, further study on the risk factors is also required to develop cost-effective preventive strategies.

Assessment of Seroprevalence and the Risk Factors of Sheep Brucellosis in Basrah (Southern Iraq): A Challenge to Prospectively Control Brucellosis

Brucellosis is one of the most important foodborne infectious diseases distributed widely in low- and middle-income countries. The current study was carried out to investigate the prevalence and risk factors that influence the distribution of Brucella in sheep. A structured questionnaire was prepared and introduced to a total of 60 resident owners from five counties, and 400 sheep blood samples were randomly collected from the selected herds. The sera of isolated sheep were tested for Brucella spp. using the Rose Bengal Test (RBT). A univariable and multivariable logistic regression analysis was used to evaluate the risk factors linked to animal management and husbandry practices at the farm level. The overall prevalence estimated for brucellosis was 31% (95% confidence interval [Cl]: 26.5–35.8). The odds of seroprevalence in sheep >1 year were significantly higher than those in sheep ≤1 year (odds ratio [OR]: 2.2, 95% Cl: 1.41–3.44). The logistic regression outcomes revealed that two variables related to the management and practices at the farm level were significantly associated with the seroprevalence of brucellosis. These variables were sheep sheep grazing with other flocks (OR: 5.8, 95 Cl% Cl: 1.53–22.67) and the practice of lending ram among sheep owners (OR: 9.3, 95% Cl: 1.05–83.82). Unconfined domesticated dogs, improper handling of aborted ewes, introduction of new animals in a herd, (purchased), and lack of knowledge about brucellosis among owners were underlined to be further important factors that could influence the spread of brucellosis. This study concluded that brucellosis is an endemic disease in Basrah, and the animal vaccination control program with an integrated health education program for sheep owners are obligatory elements of the prevention measures needed to be established to minimize the risk of brucellosis in Basrah.

Non-adaptive Evolution of Trimeric Autotransporters in Brucellaceae

Brucella species are Gram-negative, facultative intracellular pathogens. They are the main cause of brucellosis, which has led to a global health burden. Adherence of the pathogen to the host cells is the first step in the infection process. The bacteria can adhere to various biotic and abiotic surfaces using their outer membrane proteins. Trimeric autotransporter adhesins (TAAs) are modular homotrimers of various length and domain complexity. They are a diverse, and widespread gene family constituting the type Vc secretion pathway. These adhesins have been established as virulence factors in Brucellaceae. To date, no comprehensive and exhaustive study has been performed on the trimeric autotransporter family in the genus. In the present study, various bioinformatics tools were used to provide a novel evolutionary insight into the sequence and structure of this protein family in Brucellaceae. To this end, a dataset of all trimeric autotransporters from the Brucella genomes was built. Analyses included but were not limited to sequence alignment, phylogenetic tree constructions, codon-based test for selection, clustering of the sequences, and structure (primary to quaternary) predictions. Batch analyzes of the dataset suggested the existence of a few structural domains within the whole population. BatA from the B. abortus 2308 genome was selected as a reference to describe the features of these structural domains. Furthermore, we examined the structural basis for the observed rigidity and resiliency of the protein structure through a molecular dynamics evaluation, which led us to deduce that the random drift results in the non-adaptive evolution of the trimeric autotransporter genes in the Brucella genus. Notably, the modifications have occurred across the genus without interference of gene transmission.

Sero-prevalence and associated risk factors of bovine brucellosis in Sendafa, Oromia Special Zone surrounding Addis Ababa, Ethiopia

Bovine brucellosis is an infectious bacterial disease caused by members of genus Brucella, affecting both animals and humans, and resulting in a serious economic loss in animal production sector and deterioration of public health. A cross-sectional study was conducted from November 2014 to April 2015 to determine the seroprevalence and associated risk factors of bovine brucellosis in Sendafa, Oromia Special Zone, Ethiopia. A total of 503 blood samples were collected using a simple random sampling technique from dairy cattle of above 6 months of age with no history of previous vaccination against brucellosis. All sera samples were subjected to both Rose Bengal Plate Test for screening and Complement Fixation Test for confirmation. Accordingly, the overall seroprevalence of bovine brucellosis in the study area was 0.40%. The result showed that the seroprevalence of bovine brucellosis in the study area was not statistically significant with all proposed risk factors. No reactors were observed in male animals. The seroprevalence was observed in animals without previous history of abortion. Moreover, information was gathered on individual animal and farm-level risk factors and other farm characteristics using a questionnaire. Awareness among society was poor, so the positive animals can be a potential hazard to animals and humans in the study area. Therefore, public education should be done to improve the awareness of the community on bovine brucellosis and its public health impact with due consideration on the safe consumption of food of animal origin.

The Role of Neutrophils in Brucellosis

Brucellosis is a bacterial disease of domestic animals and humans. The pathogenic ability of Brucella organisms relies on their stealthy strategy and their capacity to replicate within host cells and to induce long-lasting infections. Brucella organisms barely induce neutrophil activation and survive within these leukocytes by resisting microbicidal mechanisms. Very few Brucella-infected neutrophils are found in the target organs, except for the bone marrow, early in infection. Still, Brucella induces a mild reactive oxygen species formation and, through its lipopolysaccharide, promotes the premature death of neutrophils, which release chemokines and express "eat me" signals. This effect drives the phagocytosis of infected neutrophils by mononuclear cells that become thoroughly susceptible to Brucella replication and vehicles for bacterial dispersion. The premature death of the infected neutrophils proceeds without NETosis, necrosis/oncosis, or classical apoptosis morphology. In the absence of neutrophils, the Th1 response exacerbates and promotes bacterial removal, indicating that Brucella-infected neutrophils dampen adaptive immunity. This modulatory effect opens a window for bacterial dispersion in host tissues before adaptive immunity becomes fully activated. However, the hyperactivation of immunity is not without a price, since neutropenic Brucella-infected animals develop cachexia in the early phases of the disease. The delay in the immunological response seems a sine qua non requirement for the development of long-lasting brucellosis. This property may be shared with other pathogenic alphaproteobacteria closely related to Brucella We propose a model in which Brucella-infected polymorphonuclear neutrophils (PMNs) function as "Trojan horse" vehicles for bacterial dispersal and as modulators of the Th1 adaptive immunity in infection.

Meta-analysis of brucellosis vaccinology in natural hosts

ABSTRACT: Brucellosis is a relevant zoonotic disease for which the most important tool for control is vaccination of susceptible animals. Assessment of vaccine efficacy in natural hosts is based on prevention of abortion and Brucella infection in organs of immunized animals. A meta-analysis of experimental vaccination of Brucella spp. natural hosts was performed, including 45 PubMed and/or Scopus-indexed publications, representing 116 individual experiments. Difference of risk was calculated as an indicator of protection, and a temporal analysis (1980-2016) demonstrated that experimental vaccines tested on natural hosts provided levels of protection that were stable over the past decades. The meta-regression model developed in this study included different vaccine categories (attenuated, inactivated, mutant, subunit, and vectored) considering the difference of risk as the dependent variable. The subcutaneous route of vaccination provided better protection when compared to the intramuscular and oral routes of vaccination. Surprisingly, inactivated vaccines provided better protection than live naturally attenuated vaccine strains (spontaneous mutations) that were considered the reference, whereas subunit vaccines provided lower levels of protection. This is the first meta-analysis of Brucella vaccinology in the natural hosts. These results are useful for the development of new vaccination protocols for controlling animal brucellosis.

Co-infection by Neopora caninum and bovine viral diarrhea virus in cattle from Rio Grande do Sul, Brazil, destined to exportation

ABSTRACT: Reproductive tests in cattle are of great economic importance, given the impact it can have on the production system and may be caused by agents. Neospora caninum and Bovine Viral Diarrhea virus (BVDV) are considered of great importance as reproductive and should be considered responsible for keeping animals persistently infected. The present study included 479 calf serum samples for export in the state of Rio Grande do Sul (RS). All samples were screened for BVDV by an ELISA antigen. BVDV antigen-positive ELISA samples were isolated from BVDV in cell culture. An indirect immunofluorescence (IFT) technique was used to detect anti-N. caninum antibodies. Of the 479 export-treated serum samples, 361 were positive for BVDV antigens by ELISA and/or viral isolation test (361/479-75.36%), and 109 IFT-positive samples for N. caninum (109/479-22.75%). Despite detection of antibodies anti-N. caninum did not differ statistically between naturally infected BVDV and non-BVDV infected animals suggesting that there is no interference of BVDV infection on infection or detection rate of animals with N. caninum, positive animals in viral isolation and high DO in BVDV-Ag ELISA. may present active disease and consequent immunosuppression, contributing to a potential reactivation of N. caninum.

Immune responses and clinical effects of experimental challenge of elk with Brucella abortus strain 2308

To assess the effects of challenge dose and stage of gestation on infection and abortion, 35 elk were conjunctivally challenged with virulent Brucella abortus strain 2308 (S2308) during pregnancy. Seventeen elk were experimentally challenged early in the second trimester of gestation (December) with high (approximately 10⁸ CFU) or low challenge (approximately 10⁷ CFU) treatments having 8 and 9 pregnant elk, respectively. Other pregnant elk were experimentally challenged at a later challenge time (approximately early third trimester, February), with high and low challenge treatments having 8 and 10 elk, respectively. Conjunctival swabs from all animals were culture positive for the S2308 strain at 7 days after experimental challenge. All animals seroconverted on a B. abortus ELISA but optical density readings were not influenced (P > 0.05) by time of challenge or by challenge dosage. In the early challenge group, abortions occurred in 2 of 9 (22%) in the low challenge treatment and 3 of 8 (37%) in the high challenge treatment, whereas in the later challenge group, 1 of 8 (12.5%) in the low challenge treatment and 2 of 10 (20%) in the high challenge treatment aborted. The ability to recover B. abortus from samples obtained at necropsy did not differ (P > 0.05) between early and late challenges or between high and low challenge treatments. Despite the lack of abortions observed after experimental challenge, recovery from maternal tissues ranged from 50% (low dose, late challenge) to 77% (low dose, early challenge). Our data suggests that naïve elk do not abort as frequently after experimental infection with B. abortus strain 2308 as compared to similar data in cattle and bison.

Shedding of Brucella melitensis happens through milk macrophages in the murine model of infection

Although shedding of zoonotic brucellae in milk has been demonstrated in natural hosts, these data are still missing for the standard murine infection model. We therefore analysed shedding kinetics and the niche of B. melitensis in murine milk. Pregnant Balb/cByJ mice were intraperitoneally infected with 10⁵ CFU of the 16 M reference strain, a 16 M mCherry mutant or a human isolate. Milk was collected over the course of lactation, and subjected to culture and immunofluorescence assays. Bacteria were also quantified in spleen and mammary glands of maternal mice and in spleen of the litter. The shedding of the three strains did not differ significantly (p = 0.301), ranging from log₁₀ 1.5 to 4.04 CFU/ml. A total of 73% of the mice excreted B. melitensis into the milk with peak values at mid-lactation; up to 30 bacteria/cell were found in macrophages and neutrophils. While the bacterial counts in the spleen of lactating females confirmed a well-established infection, only 50% of the pups harboured brucellae in their spleen, including the spleen of an uninfected pup fed by an infected foster mother. In conclusion, the murine model of infection may contribute to a better understanding of the zoonotic transmission of brucellosis.

Brucella abortus Proliferates in Decidualized and Non-Decidualized Human Endometrial Cells Inducing a Proinflammatory Response

Brucella spp. have been associated with abortion in humans and animals. Although the mechanisms involved are not well established, it is known that placental Brucella infection is accompanied by inflammatory phenomena. The ability of Brucella abortus to infect and survive in human endometrial stromal cells (T-HESC cell line) and the cytokine response elicited were evaluated. B. abortus was able to infect and proliferate in both non-decidualized and decidualized T-HESC cells. Intracellular proliferation depended on the expression of a functional virB operon in the pathogen. B. abortus internalization was inhibited by cytochalasin D and to a lower extent by colchicine, but was not affected by monodansylcadaverine. The infection did not induce cytotoxicity and did not alter the decidualization status of cells. B. abortus infection elicited the secretion of IL-8 and MCP-1 in either decidualized or non-decidualized T-HESC, a response also induced by heat-killed B. abortus and outer membrane vesicles derived from this bacterium. The stimulation of T-HESC with conditioned media from Brucella-infected macrophages induced the production of IL-6, MCP-1 and IL-8 in a dose-dependent manner, and this effect was shown to depend on IL-1β and TNF-α. The proinflammatory responses of T-HESC to B. abortus and to factors produced by infected macrophages may contribute to the gestational complications of brucellosis.

The Role of the Flagellar Protein FlgJ in the Virulence of Brucella abortus

Brucella abortus is a facultative intracellular pathogen that causes a zoonosis called brucellosis. This disease leads to abortion and infertility in cattle, and diverse complications in humans. B. abortus is a successful intracellular bacterium that has developed the ability to evade the host's immune system and it replicates in professional and non-professional phagocytic cells, persisting in the different tissues, and organs of its hosts. It has been described that Brucella expresses a polar flagellum under certain conditions, but its function is still unknown. In this study we evaluated the role of the FlgJ, a protein, presumably a peptidoglycan hydrolase involved in flagellum formation and in the virulence of B. abortus strain 2308. B. abortus 2308 ΔflgJ mutant and complemented strains were constructed to study the function of the FlgJ protein in the context of the virulence of this pathogen in in vitro and in vivo assays. The results showed that the elimination of the flgJ gene delays the growth rate of B. abortus in culture, reduces its intracellular survival capacity in professional and non-professional phagocytic cells, rendering it unable to escape from the endocytic route and not reaching the endoplasmic reticulum. It also negatively affects their persistence in BALB/c mice. Functionally, the B. abortus 2308 flgJ gene restored motility to an E. coli flgJ mutant gene. Furthermore, it was discovered that the production of FlgJ protein is associated with the bacterial adherence by B. abortus. Therefore, although the specific function of the polar flagellum for Brucella is unknown, the data indicates that the flagellar flgJ gene and its product are required for full virulence of B. abortus 2308, since its deletion significantly reduces the fitness of this pathogen in vitro and in vivo.

Adenosine receptor Adora2b antagonism attenuates Brucella abortus 544 infection in professional phagocyte RAW 264.7 cells and BALB/c mice

Brucella as a stealthy intracellular pathogen avoids activation of innate immune response. Here we investigated the contribution of an adenosine receptor, Adora2b, during Brucella infection in professional phagocyte RAW 264.7 cells and in a murine model. Adora2b-deficient cells showed attenuated Brucella internalization and intracellular survival with enhanced release of IL-6, TNF-α, IL-12 and MCP-1. In addition, blockade of Adora2b using MRS 1754 treatment in mice resulted in increased total weight of the spleens but suppressed bacterial burden in these organs accompanied by elevated levels of IL-6, IFN-γ, TNF-α, IL-12 and MCP-1, while reduced IL-10. Overall, we proposed that the Adora2b participates in the successful phagocytic pathway and intracellular survival of Brucella in RAW 264.7 cells, and could be a potential therapeutic target for the treatment of acute brucellosis in animals.

Elicitation of Th1/Th2 related responses in mice by chitosan nanoparticles loaded with Brucella abortus malate dehydrogenase, outer membrane proteins 10 and 19

Brucella spp. is the causative agent of brucellosis, one of the worldwide diseases. The pathogen infects humans and animals mainly through the digestive or respiratory tract. Therefore, induction of mucosal immunity is required as the first line of defense. In this study, three Brucella abortus recombinant proteins, malate dehydrogenase (rMdh), outer membrane proteins (rOmp) 10 and 19 were loaded in mucoadhesive chitosan nanoparticles (CNs) and induction of mucosal and systemic immunity were investigated after intranasal immunization of BALB/c mice. These antigens were also coimmunized as cocktail (rCocktail) to evaluate multiple antigen specific vaccine candidates. At 6-weeks post-immunization (wpi), antigen specific total IgG was increased in all of the immunized groups, predominantly IgG1. In addition, spleenocyte from rMdh-, rOmp19-, and rCocktail-immunized groups significantly produced IFN-γ and IL-4 suggesting the induction of a mixed Th1-Th2 response. For mucosal immunity, anti-Mdh IgA from nasal washes and fecal excretions, and anti-Omps IgA from sera, nasal washes, genital secretions and fecal excretions were significantly increased in single antigen immunized groups. In the rCocktail-immunized group, anti-Mdh IgA were significantly increased while anti-Omps IgA was not. Collectively, this study indicates that comprise of B. abortus antigen-loaded CNs elicited the antigen-specific IgA with a Th2-polarized immune responses and combination of the highly immunogenic antigens elicited IgG specific to each type of antigen.