Brucellosis and One Health: Inherited and Future Challenges

An Evaluation of the Lineage of Brucella Isolates in Turkey by a Whole-Genome Single-Nucleotide Polymorphism Analysis

Brucellosis is a disease caused by the Brucella (B.) species. It is a zoonotic disease that affects farm animals and causes economic losses in many countries worldwide. Brucella has the ability to persist in the environment and infect the host at low doses. Thus, it is more important to trace brucellosis outbreaks, identify their sources of infection, and interrupt their transmission. Some countries already have initial data, but most of these data are based on a Multiple-Locus Variable-Number Tandem-Repeat Analysis (MLVA), which is completely unsuitable for studying the Brucella genome. Since brucellosis is an endemic disease in Turkey, this study aimed to examine the genome of Turkish Brucella isolates collected between 2018 and 2020, except for one isolate, which was from 2012. A total of 28 strains of B. melitensis (n = 15) and B. abortus (n = 13) were analyzed using a core-genome single-nucleotide polymorphism (cgSNP) analysis. A potential connection between the Turkish isolates and entries from Sweden, Israel, Syria, Austria, and India for B. melitensis was detected. For B. abortus, there may be potential associations with entries from China. This explains the tight ties found between Brucella strains from neighboring countries and isolates from Turkey. Therefore, it is recommended that strict measures be taken and the possible effects of uncontrolled animal introduction are emphasized.

Seroprevalence of human brucellosis in Turkey: A comprehensive meta-analysis

AIMS

Brucellosis remains a common zoonotic disease, in developing countries, as well as in Turkey where it is endemic, underdiagnosed, and underreported. The aim of this meta-analysis was to provide a comprehensive estimate of seroprevalence with a large sample size, covering all regions of Turkey, including both grey literature and published studies.

METHODS AND RESULTS

A systematic search was performed in MEDLINE (via PubMed), TürkMedline (National Health Sciences-Periodicals Database), and YÖKSİS database (Higher Education Council Information System) until May 5th, 2023. The quality of the studies was evaluated independently using Joanna Briggs Institute (JBI) critical assessment tool for prevalence studies. A random-effects model (DerSimion and Laird) was utilized to estimate the overall pooled prevalence. A sensitivity analysis was performed, excluding studies with a high risk of bias. The subgroup analyses and meta-regression were conducted to explore sources of heterogeneity. Egger test and funnel plot were used to assess publication bias. The meta-analysis included 30 studies in total published between 1999 and 2021 with 51,560 individuals. In Turkey, the pooled seroprevalence of human brucellosis was estimated to be 4.5% (95% confidence interval [CI]: 3.8%-5.3%). According to the subgroup analysis, a higher seroprevalence was found in rural areas (8.0%, 95% CI: 5.4%-10.7%), high-risk occupational groups (9.9%, 95% CI: 5.3%-14.6%), and the Central East Anatolia Region (13%, 95% CI: 3.2%-22.8%). The meta-regression analysis identified living in rural areas and certain geographic regions as significant risk factors associated with higher seroprevalence.

CONCLUSIONS

This meta-analysis revealed a significant burden of human brucellosis in Turkey. The findings highlight the need for public health measures and targeted interventions to reduce the burden of this zoonotic disease, especially in rural areas, high-risk occupational groups, and the East Anatolia Region.

Brucellosis: Unveiling the complexities of a pervasive zoonotic disease and its global impacts

One zoonotic infectious animal disease is brucellosis. The bacteria that cause brucellosis belong to the genus Brucella. Numerous animal and human species are affected by brucellosis, with an estimated 500,000 human cases recorded annually worldwide. The occurrence of new areas of infection and the resurgence of infection in already infected areas indicate how dynamically brucellosis is distributed throughout different geographic regions. Bacteria originate from the blood and are found in the reticuloendothelial system, the liver, the spleen, and numerous other locations, including the joints, kidneys, heart, and genital tract. Diagnosis of this disease can be done by bacterial isolation, molecular tests, modified acid-fast stain, rose bengal test (RBT), milk ring test, complement fixation test, enzyme-linked immunosorbent assay, and serum agglutination test. The primary sign of a Brucella abortus infection is infertility, which can result in abortion and the birth of a frail fetus that may go on to infect other animals. In humans, the main symptoms are acute febrile illness, with or without localization signs, and chronic infection. Female cattle have a greater risk of contracting Brucella disease. Human populations at high risk of contracting brucellosis include those who care for cattle, veterinarians, slaughterhouse employees, and butchers. Antibiotic treatment of brucellosis is often unsuccessful due to the intracellular survival of Brucella and its adaptability in macrophages. A "one health" strategy is necessary to control illnesses like brucellosis.

Seroepidemiology and associated risk factors of brucellosis in small ruminants of district Khanewal, Pakistan

Objectives

Keeping in view the economic and veterinary public health importance of brucellosis, this research was conducted to determine its seroprevalence and associated risk determinants in small ruminants in district Khanewal, Southern Punjab, Pakistan.

Materials and Methods

Two-stage cluster sampling technique was used for sampling, and the sample size was calculated using C-survey 2.0. Accordingly, sera samples (n = 392) were collected from small ruminants in the study area from October 2022 to July 2023. All the samples were tested for the presence of anti-Brucella antibodies by Rose Bengal Plate Test (RBPT), followed by confirmation of all the samples using an enzyme linked immunosorbent assay (ELISA) kit (ID.vet®, France; sensitivity and specificity=100%, each).

Results

The seropositivity rate of brucellosis was 7.14% [n = 28/392; 95% confidence interval (CI) = 4.87%-10.12%] by RBPT, whereas the results of ELISA showed an overall seroprevalence rate of 7.40% (n = 29/392; 95% CI = 5.11%-10.37%) in the study population. Univariate analysis of risk factors revealed that abortion history (AH), retained fetal membranes (RFMs), repeat breeding, flock size (FS), educational status of farmers (ESFs), awareness about brucellosis (AB), and farm hygiene had a significant association with the seroprevalence of brucellosis (p < 0.05). The multivariate analysis using a binary logistic regression model revealed that variables including tehsil, FS, AH, RFM, ESF, AB, and farming system were significant factors (p < 0.05) associated with brucellosis in the target population.

Conclusion

Brucellosis is prevalent in small ruminants in Khanewal, Pakistan. The disease burden can be reduced by improving the reproductive health of animals, farm hygiene, and farmers' awareness about the diseases. Further studies are needed on a larger scale to devise stringent disease control strategies to avoid losses associated with brucellosis at regional, national, and global levels.

Characterization of three predicted zinc exporters in Brucella ovis identifies ZntR-ZntA as a powerful zinc and cadmium efflux system not required for virulence and unveils pathogenic Brucellae heterogeneity in zinc homeostasis

Brucella ovis causes non-zoonotic ovine brucellosis of worldwide distribution and is responsible for important economic losses mainly derived from male genital lesions and reproductive fails. Studies about the virulence mechanisms of this rough species (lacking lipopolysaccharide O-chains) are underrepresented when compared to the main zoonotic Brucella species that are smooth (with O-chains). Zinc intoxication constitutes a defense mechanism of the host against bacterial pathogens, which have developed efflux systems to counterbalance toxicity. In this study, we have characterized three potential B. ovis zinc exporters, including the ZntA ortholog previously studied in B. abortus. Despite an in-frame deletion removing 100 amino acids from B. ovis ZntA, the protein retained strong zinc efflux properties. Only indirect evidence suggested a higher exporter activity for B. abortus ZntA, which, together with differences in ZntR-mediated regulation of zntA expression between B. ovis and B. abortus, could contribute to explaining why the ΔzntR mutant of B. abortus is attenuated while that of B. ovis is virulent. Additionally, B. ovis ZntA was revealed as a powerful cadmium exporter contributing to cobalt, copper, and nickel detoxification, properties not previously described for the B. abortus ortholog. Deletion mutants for BOV_0501 and BOV_A1100, also identified as potential zinc exporters and pseudogenes in B. abortus, behaved as the B. ovis parental strain in all tests performed. However, their overexpression in the ΔzntA mutant allowed the detection of discrete zinc and cobalt efflux activity for BOV_0501 and BOV_A1100, respectively. Nevertheless, considering their low expression levels and the stronger activity of ZntA as a zinc and cobalt exporter, the biological role of BOV_0501 and BOV_A1100 is questionable. Results presented in this study evidence heterogeneity among pathogenic Brucellae regarding zinc export and, considering the virulence of B. ovis ΔzntA, suggest that host-mediated zinc intoxication is not a relevant mechanism to control B. ovis infection.

A review of three decades of use of the cattle brucellosis rough vaccine Brucella abortus RB51: myths and facts

Cattle brucellosis is a severe zoonosis of worldwide distribution caused by Brucella abortus and B. melitensis. In some countries with appropriate infrastructure, animal tagging and movement control, eradication was possible through efficient diagnosis and vaccination with B. abortus S19, usually combined with test-and-slaughter (T/S). Although S19 elicits anti-smooth lipopolysaccharide antibodies that may interfere in the differentiation of infected and vaccinated animals (DIVA), this issue is minimized using appropriate S19 vaccination protocols and irrelevant when high-prevalence makes mass vaccination necessary or when eradication requisites are not met. However, S19 has been broadly replaced by vaccine RB51 (a rifampin-resistant rough mutant) as it is widely accepted that is DIVA, safe and as protective as S19. These RB51 properties are critically reviewed here using the evidence accumulated in the last 35 years. Controlled experiments and field evidence shows that RB51 interferes in immunosorbent assays (iELISA, cELISA and others) and in complement fixation, issues accentuated by revaccinating animals previously immunized with RB51 or S19. Moreover, contacts with virulent brucellae elicit anti-smooth lipopolysaccharide antibodies in RB51 vaccinated animals. Thus, accepting that RB51 is truly DIVA results in extended diagnostic confusions and, when combined with T/S, unnecessary over-culling. Studies supporting the safety of RB51 are flawed and, on the contrary, there is solid evidence that RB51 is excreted in milk and abortifacient in pregnant animals, thus being released in abortions and vaginal fluids. These problems are accentuated by the RB51 virulence in humans, lack diagnostic serological tests detecting these infections and RB51 rifampicin resistance. In controlled experiments, protection by RB51 compares unfavorably with S19 and lasts less than four years with no evidence that RB51-revaccination bolsters immunity, and field studies reporting its usefulness are flawed. There is no evidence that RB51 protects cattle against B. melitensis, infection common when raised together with small ruminants. Finally, data acumulated during cattle brucellosis eradication in Spain shows that S19-T/S is far more efficacious than RB51-T/S, which does not differ from T/S alone. We conclude that the assumption that RB51 is DIVA, safe, and efficaceous results from the uncritical repetition of imperfectly examined evidence, and advise against its use.