Pathological and diagnostic investigations of abortions and neonatal mortality associated with natural infection of Brucella abortus in dromedary camels

Accuracy of molecular diagnostic methods for the detection of bovine brucellosis: A systematic review and meta-analysis

Background and Aim:

Bovine brucellosis is a disease of global socio-economic importance caused by Brucella abortus. Diagnosis is mainly based on bacterial culture and serology. However, these methods often lack sensitivity and specificity. A range of molecular diagnostic methods has been developed to address these challenges. Therefore, this study aims to investigate the diagnostic accuracy of molecular tools, in comparison to gold standard bacterial isolation and serological assays for the diagnosis of bovine brucellosis.

Materials and Methods:

The systematic review and meta-analysis were conducted based on analyses of peer-reviewed journal articles published between January 1, 1990, and June 6, 2020, in the PubMed, Science Direct, Scopus, and Springer Link databases. Data were extracted from studies reporting the use of molecular diagnostic methods for the detection of B. abortus infections in animals according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The quality of included journal articles was assessed using the quality assessment of diagnostic-accuracy studies assessment tool and meta-analysis was carried out using Review Manager.

Results:

From a total of 177 studies, only 26 articles met the inclusion criteria based on PRISMA guidelines. Data from 35 complete studies were included in the meta-analysis and used to construct 2 × 2 contingency tables. Improved diagnostic performance was observed when tissue (sensitivity 92.7% [95% confidence interval (CI) 82.0–98.0%]) and serum samples (sensitivity 91.3% [95% CI 86.0–95.0%]) were used, while the BruAb2_0168 locus was the gene of preference for optimal assay performance (sensitivity 92.3% [95% CI 87.0–96.0%] and specificity 99.3% [95% CI 98.0–100.0%]). Loop-mediated isothermal amplification (LAMP) had a higher diagnostic accuracy than polymerase chain reaction (PCR) and real-time quantitative PCR with sensitivity of 92.0% (95% CI 78.0–98.0%) and specificity of 100.0% (95% CI 97.0–100.0%).

Conclusion:

The findings of this study assign superior diagnostic performance in the detection of B. abortus to LAMP. However, due to limitations associated with decreased specificity and a limited number of published articles on LAMP, the alternative use of PCR-based assays including those reported in literature is recommended while the use of LAMP for the detection of bovine brucellosis gains traction and should be evaluated more comprehensively in future.

Seroprevalence trend of human brucellosis and MLVA genotyping characteristics of Brucella melitensis in Shaanxi Province, China, during 2008-2020

In this study, a total of 179,907 blood samples from populations with suspected Brucella spp. infections were collected between 2008 and 2020 and analyzed by the Rose Bengal plate test (RBPT) and serum agglutination test (SAT). Moreover, conventional biotyping, B. abortus-melitensis-ovis-suis polymerase chain reaction (AMOS-PCR), and multiple-locus variable-number tandem repeat analysis (MLVA) was applied to characterize the isolated strains. A total of 8103 (4.50%) samples were positive in RBPT, while 7705 (4.28%, 95% confidence interval (CI) 4.19-4.37) samples were positive in SAT. There was a significant difference in seroprevalence for human brucellosis over time, in different areas and different cities (districts) (χ² = 2 = 32.23, 1984.14, and 3749.51, p < .05). The highest seropositivity (8.22% (4, 965/60393; 95% CI 8.00-8.44) was observed in Yulin City, which borders Inner Mongolia, Ningxia, and Gansu Province, China, regions that have a high incidence of human brucellosis. Moreover, 174 Brucella strains were obtained, including nine with B. melitensis bv. 1, 145 with B. melitensis bv. 3, and 20 with B. melitensis variants. After random selection, 132 B. melitensis were further genotyped using MLVA-16. The 132 strains were sorted into 100 MLVA-16 genotypes (GTs) (GT 1-100), 81 of which were single GTs represented by singular independent strains. The remaining 19 shared GTs involved 51 strains, and each GT included two to seven isolates from the Shaan northern and Guanzhong areas. These data indicated that although sporadic cases were a dominant epidemic characteristic of human brucellosis in this province, more than 38.6% (51/132) outbreaks were also found in the Shaan northern area and Guanzhong areas. The 47 shared MLVA-16 GTs were observed in strains (n = 71) from this study and strains (n = 337) from 19 other provinces of China. These data suggest that strains from the northern provinces are a potential source of human brucellosis cases in Shaanxi Province. It is urgent to strengthen the surveillance and control of the trade and transfer of infected sheep among regions.

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

Background: Brucellosis is an important zoonotic disease caused by Brucella spp. Brucellosis is widely distributed in more than 160 or 170 countries around the world, where it poses a huge threat to animal husbandry and human health. About 150 million head of water buffalo, distributed across more than 40 countries worldwide, are kept for the purposes of service, milk, and meat. High incidence of Brucella spp. in buffalo has negatively affected dairy products and meat products.

Results: We searched all research related to seroprevalence of brucellosis in water buffalo anywhere in the world in PubMed, Science Direct, SpringerLink, China National Knowledge Infrastructure, Wanfang Database, and VIP Chinese Journal Databases. A total of 26 articles published from 1985 to 2020 met the final selection criteria. The overall seroprevalence of buffalo brucellosis worldwide was 9.7%. The seroprevalence before 2010 (20.8%) (95% CI: 5.6–42.2) was much higher than the seroprevalence rate from 2010 to 2020 (4.2%) (95% CI: 1.8–7.5). Subgroup analysis by feeding mode found that the point estimate of seroprevalence in stock buffalo (11.5%) (95% CI: 3.6–23.0) was higher than that in captive buffalo (10.6%) (95% CI: 4.9–18.1). Subgroup analysis by farming mode found that the seroprevalence was higher in captive-bred buffalo (10.7%) (95% CI: 6.6–15.7) than in intensively farmed buffalo (8.5) (95% CI: 0.9–22.2). The seroprevalence in buffalo living in dry lands (6.4%) (95% CI: 2.0–12.9) is greater than that in buffalo living in wetlands (5.1%) (95% CI: 1.8–10.4) (P < 0.05). The seroprevalence in female buffalo (10.1%) (95% CI: 3.4–19.7) was higher than that in male buffalo (4.4%) (95% CI: 2.0–7.4). The seroprevalence in lactating buffalo was higher than that in buffalo of other ages (26.9%) (95% CI: 1.8–66.5). Subgroup analysis by detection method found that the seroprevalence detected by the complement fixation test (27.3%) (95% CI: 0.7–70.8) was much higher than that detected by other methods.

Conclusion: The results of this meta-analysis showed that buffalo brucellosis infection is very common in buffalo herds around the world. Although the seroprevalence of brucellosis in buffalo and humans is relatively low, serious effects upon animal husbandry and public health make it necessary to take effective control and preventive measures to control the spread of this disease.

Considerations for the development of a dromedary camel (Camelus dromedarius) semen collection centre

The dromedary camel (DC) is a strategic animal for the exploitation of the desert and unhospitable lands (arid and semiarid areas). These animals are a genetic resource, locally adapted and more resilient to these environs, that may significantly contribute to food security and sustainable development of marginal land areas. Artificial insemination is the least invasive, least expensive technique for improving genetic selection and minimising transmission of venereal disease among animals and herds. Besides semen preservation protocols, specific approaches for the development of DC semen collection centres - biosecurity measures, screening for infectious diseases, management of animals, welfare, nutrition, control of seasonality, training, hygiene of semen collection and processing - have been considered less important aspects. The aim of this research is to describe the aspects related to the development of a DC semen collection centre, summarising the latest studies in the field of welfare, reproduction and diseases, and describing biosecurity and hygiene aspects related to semen collection and handling. Scientific gaps and requirements for maximising the production of good quality and safe-to-use semen doses with minimal risks of disease transmission are also described.

An Overview of Brucellosis in Cattle and Humans, and its Serological and Molecular Diagnosis in Control Strategies

Brucellosis is one of the most common contagious and communicable zoonotic diseases with high rates of morbidity and lifetime sterility. There has been a momentous increase over the recent years in intra/interspecific infection rates, due to poor management and limited resources, especially in developing countries. Abortion in the last trimester is a predominant sign, followed by reduced milk yield and high temperature in cattle, while in humans it is characterized by undulant fever, general malaise, and arthritis. While the clinical picture of brucellosis in humans and cattle is not clear and often misleading with the classical serological diagnosis, efforts have been made to overcome the limitations of current serological assays through the development of PCR-based diagnosis. Due to its complex nature, brucellosis remains a serious threat to public health and livestock in developing countries. In this review, we summarized the recent literature, significant advancements, and challenges in the treatment and vaccination against brucellosis, with a special focus on developing countries.

African Lineage Brucella melitensis Isolates from Omani Livestock

Brucellosis is a common livestock disease in the Middle East and North Africa, but remains poorly described in the region both genetically and epidemiologically. Traditionally found in goats and sheep, Brucella melitensis is increasingly recognized as infecting camels. Most studies of brucellosis in camels to date have focused on serological surveys, providing only limited understanding of the molecular epidemiology of circulating strains. We genotyped B. melitensis isolates from Omani camels using whole genome SNP assays and VNTRs to provide context for regional brucellosis cases. We identified a lineage of B. melitensis circulating in camels as well as in goats, sheep, and cattle in Oman. This lineage is genetically distinct from most genotypes from the Arabian Peninsula and from isolates from much of the rest of the Middle East. We then developed diagnostic assays that rapidly identify strains from this lineage. In analyses of genotypes from throughout the region, Omani isolates were genetically most closely related to strains from brucellosis cases in humans and livestock in North Africa. Our findings suggest an African origin for B. melitensis in Oman that has likely occurred through the trade of infected livestock. Moreover, African lineages of B. melitensis appear to be undersampled and consequently are underrepresented in genetic databases for Brucella. As we begin to more fully understand global genomic diversity of B. melitensis, finding and characterizing these unique but widespread lineages is essential. We predict that increased sampling of humans and livestock in Africa will reveal little known diversity in this important zoonotic pathogen.