Seroprevalence of Brucellosis in Buffalo Worldwide and Associated Risk Factors: A Systematic Review and Meta-Analysis

Human and animal brucellosis and risk factors for human infection in Ethiopia: a systematic review and meta-analysis (2015-2024)

BACKGROUND AND OBJECTIVE

Brucellosis is a neglected zoonotic disease caused by Brucella species. Unlike most developed nations, the problem of brucellosis in Ethiopia remains a public and animal health concern. This study was conducted to determine the magnitude of brucellosis in animals (mainly cattle, sheep, goats, dogs and camels) and humans, and to identify the risk factors for human brucellosis.

METHODOLOGY

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to conduct this systematic review and meta-analysis, which was performed from May 2024 to July 2024. Academic databases such as PubMed, ScienceDirect, Scopus, PubMed Central, Web of Science, and Google Scholar were searched to identify articles focusing on brucellosis in humans and animals in Ethiopia. Data extraction was performed according to predefined inclusion and exclusion criteria. The included articles were appraised using the appraisal tool for cross-sectional studies to assess study quality. Publication bias and small study effects were examined using funnel plot observation and Egger's test, respectively. Statistical analysis was conducted using R software version 4.4.1.

RESULTS

Thirty-nine articles published between 2015 and 2024 were included in the final analysis from a total of 1,427 identified articles. The overall pooled seroprevalence of brucellosis was 5.0% (95% CI: 3.0, 6.0). The seroprevalence of brucellosis was higher in humans at 6.9% (95% CI: 4.9, 8.8) and lower in cattle at 3.5% (95% CI: 2.2, 4.7). There was high heterogeneity in the reports of brucellosis seroprevalence between studies (τ² = 0.0038, H² = 255.9, I² = 99.61%, Q-test = 1954.99, df = 56, p ≤ 0.001). Laboratory tests and study location were identified as factors contributing to potential sources of variation in the pooled seroprevalence. Drinking raw milk from aborted animals, touching aborted materials or fetuses, and occupation were among the risk factors for human brucellosis. No publication bias or small study effects were detected.

CONCLUSION

The findings indicate that brucellosis continues to pose a significant zoonotic threat, particularly to humans, where the seroprevalence is notably higher than in animals. These results highlight the need for targeted public health interventions and greater awareness to reduce the incidence of brucellosis, especially among high-risk populations.

Seroprevalance of Brucellosis and Q-fever in water buffaloes (Bubalus bubalis) in Haryana state, India

Brucellosis and Q-fever are two highly contagious bacterial diseases with significant zoonotic potential and economic threats, yet they often remain underreported and neglected in low- and middle-income countries. The present study aimed to determine the seroprevalence of Brucellosis and Q-fever in water buffaloes in the Haryana state of India to implement effective preventive measures for disease control. The study covered all 22 districts of Haryana and involved 400 serum samples collected from female buffaloes belonging to two age groups and three distinct agro-climatic zones. The collected sera were tested using the Rose Bengal Plate agglutination test (RBPT) and commercial indirect enzyme linked immunosorbent assay (i-ELISA) for the presence of antibodies against smooth strains of Brucella spp. Additionally, the same serum samples were examined by i-ELISA for antibodies against Coxiella burnetii. The overall seroprevalence of brucellosis was observed as 8.25% (CI: 5.75-11.39) using the RBPT and 7.5% (CI: 5.12-10.53) by i-ELISA. The overall observed seroprevalence of Q-fever was 2.00% (CI: 0.87-3.90). No significant variation was seen in seropositivity of both diseases based on age and agroclimatic zones of the state. The findings of this study provide critical insights to farmers, agricultural organizations, veterinary services, and healthcare providers, facilitating more effective implementation of disease control measures.

The virome of bubaline (Bubalus bubalis) tonsils reveals an unreported bubaline polyomavirus

Water buffalo (Bubalus bubalis) farming is increasing in many regions of the world due to the species' ability to thrive in environments where bovine cattle would struggle. Despite water buffaloes being known for their resistance to diseases, there is a lack of data about the diversity of the microbiome of the species. In this study, we examined the virome diversity in palatine tonsils collected from animals from the island of Marajó, northern Pará state, Brazil, which harbors the largest bubaline flock in the country. Tonsil fragments from 60 clinically healthy bubalines were randomly selected from a sample of 293 animals. The samples were purified, extracted, and randomly amplified with phi29 DNA polymerase. After amplification, the products were purified and sequenced. Circular DNA viruses were predominant in the tonsils' virome. Sequences of genome segments representative of members of the genera Alphapolyomavirus (including a previously unreported bubaline polyomavirus genome) and Gemycircularvirus were identified, along with other not yet classified circular virus genomes. As the animals were clinically healthy at the time of sampling, such viruses likely constitute part of the normal tonsillar virome of water buffaloes inhabiting the Ilha do Marajó biome.

Concomitant Treatment with Doxycycline and Rifampicin in Balb/c Mice Infected with Brucella abortus 2308 Fails to Reduce Inflammation and Motor Disability

Brucellosis is an infection widely distributed around the world, and in some countries it is considered a public health problem. Brucellosis causes insidious symptoms that make it difficult to diagnose. Infection can also trigger chronic pain and neuropsychiatric complications. Antibiotics are not always effective to eradicate infection, contributing to chronicity. We aimed to investigate the effects of antibiotic treatment on proinflammatory cytokines, neurotransmitters, corticosterone, and behavior in a murine model of infecrion of B. abortus strain 2308. Four study groups were created: (a) control; (b) antibiotic control; (c) infected with B. abortus 2308; and (d) infected and treated with rifampicin and doxycycline. We determined B. abortus 2308 colony-forming units (CFUs), the count of dendritic cells, and macrophages in the spleen; serum levels of cytokines and corticosterone; levels of serotonin, dopamine, epinephrine, and norepinephrine in the brain; and equilibrium, physical strength, anxiety, and hopelessness tests. The infected and treated mice group was compared with the control and infected mice to assess whether treatment is sufficient to recover neuroimmunoendocrine parameters. Our results showed that despite the treatment of brucellosis with rifampicin and doxycycline, antibiotic-treated mice showed a persistence of B. abortus 2308 CFUs, an increased count in macrophage number, and higher circulating levels of corticosterone. Furthermore, the levels of IL-12, IL-6, and TNF-α remained higher. We found a decrease in muscular strength and equilibrium concomitant to changes in neurotransmitters in the hippocampus, cerebellum, and frontal cortex. Our data suggest that the remaining bacterial load after antibiotic administration favors inflammatory, neurochemical, and behavioral alterations, partly explaining the widespread and paradoxical symptomatology experienced by patients with chronic brucellosis.

Brucellosis and One Health: Inherited and Future Challenges

One Health is the collaborative efforts of multiple disciplines to attain optimal health for people, animals and the environment, a concept that historically owes much to the study of brucellosis, including recent political and ethical considerations. Brucellosis One Health actors include Public Health and Veterinary Services, microbiologists, medical and veterinary practitioners and breeders. Brucellosis awareness, and the correct use of diagnostic, epidemiological and prophylactic tools is essential. In brucellosis, One Health implementation faces inherited and new challenges, some aggravated by global warming and the intensification of breeding to meet growing food demands. In endemic scenarios, disease awareness, stakeholder sensitization/engagement and the need to build breeder trust are unresolved issues, all made difficult by the protean characteristics of this zoonosis. Extended infrastructural weaknesses, often accentuated by geography and climate, are critically important. Capacity-building faces misconceptions derived from an uncritical adoption of control/eradication strategies applied in countries with suitable means, and requires additional reference laboratories in endemic areas. Challenges for One Health implementation include the lack of research in species other than cattle and small ruminants, the need for a safer small ruminant vaccine, the need to fill in the infrastructure gap, the need for realistic capacity-building, the creation of reference laboratories in critical areas, and the stepwise implementation of measures not directly transposed from the so-called developed countries.

Serological and molecular prevalence of Brucella spp. among livestock species in Rajasthan, India

A seroprevalence and molecular study was carried out in six districts of the state of Rajasthan, India to detect brucellosis in major livestock species. This study involves the testing of 3,245 livestock samples using the Rose Bengal Plate Test (RBPT), Indirect Enzyme-Linked Immunosorbent Assay (i-ELISA), and genus-specific polymerase chain reaction (PCR) markers for molecular diagnosis of the disease. In the tested samples, seroprevalence was 5.06% (CI: 1.96-8.15) using the RBPT test and 6.88% (CI: 1.98-11.78) using the i-ELISA test, while the cumulative seroprevalence (RBPT and i-ELISA) was 3.63% (CI: 0.44-6.83). The prevalence of the disease was 1.27% (CI: 0.56-3.11) when tested using molecular markers. The highest prevalence of brucellosis was detected in Cattle (7.00, 3.22%), followed by camels (5.50, 2.50%), buffalo (2.66, 0.00%), sheep (2.43, 0.41%), and goats (0.58, 0.23%) when serological (cumulative) and molecular diagnosis were considered preferred methods of detection. Cattle (3.22%) and camels (2.50%) also showed a high prevalence of disease when tested using molecular markers. The results of this study reveal that cattle, camel, and sheep brucellosis is prevalent in the study areas.

Presence of Brucella spp. in Milk and Dairy Products: A Comprehensive Review and Its Perspectives

Consuming raw milk and milk-based products that have not been produced under strict control conditions can cause brucellosis, a highly contagious zoonotic disease. It is a significant global public health concern, particularly in regions with poor management and limited resources, such as Latin America, North and East Africa, the Middle East, and South and Central Asia. The study aims to summarize the occurrence of human brucellosis linked to milk and milk products and the presence of Brucella species in dairy foods. To achieve this goal, a meta-analysis was conducted on 69 studies ranging from 2001 to 2022, which were categorized into two groups: the incidence of Brucella species in milk and milk products and the prevalence of human brucellosis resulting from the consumption of contaminated milk. The following milk and milk products showed the highest incidence of Brucella species: cow milk (1.86%–81.7%), buffalo milk (10.4%–61.67%), camel milk (0%–24%), goat milk (0%–88.8%), and cheese (0%–39.1%). Consuming unpasteurized milk and milk products has been identified as the leading cause of human brucellosis, with incidence rates varying from 33.9% to 100%. Several human brucellosis cases have been linked to consuming raw milk and cheese in Spain, Israel, and other countries. Various serological techniques are employed to detect Brucella-specific antibodies in milk. The milk ring test (MRT) and enzyme-linked immunoassay (ELISA) are the two most widely utilized methods for detecting these antibodies in milk. Recently developed dual biosensors are a powerful approach for early diagnosis of Brucella from milk. Real-time PCR can rapidly detect organisms, reducing the risk of lab contamination and false positive results. To prevent and control brucellosis, essential steps include proper pasteurization of milk and dairy products, using the milk ring test (MRT) to detect Brucella in individual and bulk milk, immunization, education, and increasing public awareness of the disease. The consumption of raw milk and milk-made products that are not produced under strictly controlled conditions poses a significant risk to human health, mainly due to the high incidence of Brucella contamination. Therefore, ensuring strict control measures in producing milk and milk-made products is crucial to preventing the spread of this disease and safeguarding human health.

A rapid direct-differential agglutination assay for Brucella detection using antibodies conjugated with functionalized gold nanoparticles

Brucellosis is the most widespread and serious zoonotic disease worldwide which affects livestock, sylvatic wildlife, marine dwellers, and humans. It is acquired through Alphaproteobacteria which belong to the genus Brucella and is categorized as a potential bio-threat agent. In this study, we developed a rapid and direct differential whole cell (WC) agglutination-based assay for its on-field detection. The recombinant outer membrane (rOmp28) protein-derived specific mice IgG polyclonal antibodies (pAbs) of Brucella were purified using affinity chromatography and conjugated with functionalized gold nanoparticles (AuNPs) for rapid agglutination. A positive blot of 32 kDa protein revealed specific immuno-reactivity of rOmp28-pAbs using immunoblot analysis. For the synthesis of AuNPs, the conventional “Turkevich method” was optimized at a concentration < 1 mM of gold precursor for obtaining 50-nm-sized particles. Also, their physico-chemical characteristics were analyzed using UV-visible spectrophotometry, Fourier transform infra-red spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential (ζ, ZP), and fluorescence spectroscopy. Furthermore, these AuNPs were functionalized with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to prepare modified carboxylated AuNPs. For bioconjugation with Brucella rOmp28 IgG pAbs, antibody-conjugated functionalized AuNP constructs were prepared and characterized using FT-IR analysis with strong N–H deformations. Subsequently, these bioconjugated AuNPs were used to develop a direct-differential slide agglutination assay with a detection limit of 104 CFU mL−1. The sensitivity of this assay was compared with standard double-antibody sandwich ELISA (S-ELISA) using rOmp28 IgG pAbs with an LOD of 103 CFU mL−1 and a detection range of 102–108 CFU mL−1. No intraspecies cross-reactivity was observed based on evaluation of its specificity with a battery of closely related bacterial species. In conclusion, the increased sensitivity and specificity of the developed agglutination assay obtained using bioconjugated functionalized AuNPs is ≥ 98% for the detection of Brucella. Therefore, it can be used as an alternate rapid method of direct WC detection of bacteria as it is simple, robust, and cost-effective, with minimal time of reaction in the case of early disease diagnosis.

In-depth immunophenotyping reveals significant alteration of lymphocytes in buffalo with brucellosis

Water buffalo (Bubalus bubalis) has a prominent position in the livestock industry worldwide but still suffers from limited knowledge on the mechanisms regulating the immune against infections, including brucellosis (BRC), one of the most significant neglected zoonotic diseases of livestock. Seventy-three buffalo were recruited for the study. Thirty-five were naturally infected with Brucella spp. The aims of the study were to (i) verify the cross-reactivity of 16 monoclonal antibodies (mAbs) developed against human, bovine, and ovine antigens; (ii) evaluate lymphocyte subset alterations in BRC positive buffalo; (iii) evaluate the use of the canonical discriminant analysis (CDA), with flow cytometric data, to discriminate BRC positive from negative animals. A new set of eight mAbs (anti CD3e, CD16, CD18, CD45R0, CD79a; CD172a) were shown to cross-react with water buffalo orthologous molecules. BRC positive animals presented a significant (p < 0.0001) decrease in the percentage of PBMC (29.5 vs. 40.3), total, T and B lymphocytes (23.0 vs. 35.5, 19.2 vs. 28.9, 2.6 vs. 5.7, respectively). In contrast, they showed an increase in percentage of granulocytes (65.2 vs. 55.1; p < 0.0001) and B lymphocytes CD21^neg (22.9 vs. 16.1; p = 0.0067), a higher T/B lymphocyte ratio (10.3 vs. 6.4; p = 0.0011) and CD3⁺ /CD21⁺ (14.7 vs. 8.3; p = 0.0005) ratio. The CDA, applied to 33 different flow cytometric traits, allowed the discrimination of all BRC positive from negative buffalo. Although this is a preliminary study, our results show that flow cytometry can be used in a wide range of applications in livestock diseases, including in support of uncertain BRC diagnoses.

Spatio-Temporal Distribution of Brucellosis in European Terrestrial and Marine Wildlife Species and Its Regional Implications

Brucellosis is an important bacterial zoonosis of domestic and wildlife species. This disease has a significant public health concern and is characterized by reproductive failure resulting in economic losses in the livestock industry. Among thirteen known species, B. abortus, B. melitensis, B. suis, and B. canis are human pathogens. Brucellosis has been extensively investigated in humans and domestic animals. However, the situation in wildlife is still not completely reported and studied. Therefore, a systematic literature search and screening were done to clarify the situation of brucellosis in wildlife in Europe. Sixty-five articles from a total of 13,424 reports published between 1991 and 2021 were selected, applying defined inclusion criteria. Wild boars and brown hares were the most often studied terrestrial wildlife species, whereas seals and porpoises were the most often investigated marine wildlife. Poland, Croatia, and Belgium showed the highest seroprevalences of wild boars caused by B. suis biovar 2. In marine wildlife, brucellosis was mainly caused by B. ceti and B. pinnipedialis. Most samples were from carcasses. Thus, sera could not be collected. It is worrisome that B.abortus and B. melitensis were reported from both terrestrial and marine wild animals, posing a zoonotic threat to people exposed to wild animals. Currently, there is no approved vaccine available for wild animals. The main challenges are the development of specific diagnostics and their validation for use in wildlife.

Prevalence of Leptospira in murine in China: A systematic review and meta-analysis

Leptospirosis is an acute infectious disease caused by pathogenic bacteria from the genus Leptospira. The disease is widely distributed throughout China, causing harm to human and animal health. Murine may naturally carry a variety of pathogenic Leptospira, thus being important sources of infection by humans and livestock. The aim of this study was to assess and analyse the prevalence of Leptospira and its risk factors in murine. We collected 46 publications published between inception and 2022 through China Knowledge Network (CNKI), VIP Chinese Journal Database, Wanfang Database, PubMed, and ScienceDirect. In these studies, a total of 54,051 murine in 5 regions of China were investigated, and the prevalence of leptospirosis ranged from 1.11 to 35.29%. The prevalence of murine leptospirosis in south China was the highest, at 20.13%, and the lowest in northeast China, at 1.11% (P < 0.05). The prevalence of leptospirosis in male murine was 21.38%, which was significantly higher than that in females (17.07%; P < 0.05). Results according to detection method subgroup showed that the prevalence from serological testing was 15.94%, which was significantly higher than that of etiology and molecular biology methods (P < 0.01). In the sample subgroup, the positive rate of serum samples was 15.30%, which was significantly higher than that of tissue samples, at 7.97%. In addition, the influence of different geographical factors on prevalence was analyzed, indicating that the Yangtze River Basin was a high-incidence area for leptospirosis. The study showed that Leptospira were ubiquitous throughout the country, and factors such as environment, temperature and landform affect the murine distribution and their bacteria carrying rate. We suggest strengthening the continuous monitoring of leptospirosis and taking effective and comprehensive measures such as reducing water contact, vaccinating in high-incidence seasons, and avoiding human contamination caused by water pollution and contact with infected murine.