Evaluation of the economic impact of brucellosis in domestic yaks of Tibet

A scoping review on the epidemiology and public significance of Brucella abortus in Chinese dairy cattle and humans

Brucellosis, caused by Brucella spp., is a re-emerging One Health disease with increased prevalence and incidence in Chinese dairy cattle and humans, severely affecting animal productivity and public health. In dairy cattle, B. abortus is the primary causative agent although infections with other Brucella species occur occasionally. However, the epidemiological and comparative importance of B. abortus in dairy cattle and humans remains inadequately understood throughout China due to the heterogeneity in locations, quality, and study methods. This scoping review aims to describe the changing status of B. abortus infection in dairy cattle and humans, investigate the circulating Brucella species and biovars, and identify factors driving the disease transmission by retrieving publicly accessible literature from four databases. After passing the prespecified inclusion criteria, 60 original articles were included in the final synthesis. Although the reported animal-level and farm-level prevalence of brucellosis in dairy cattle was lower compared to other endemic countries (e.g. Iran and India), it has been reported to increase over the last decade. The incidence of brucellosis in humans displayed seasonal increases. The Rose Bengal Test and Serum Agglutination Test, interpreted in series, were the most used serological test to diagnose Brucella spp. in dairy cattle and humans. B. abortus biovar 3 was the predominant species (81.9%) and biovar (70.3%) in dairy cattle, and B. melitensis biovar 3 was identified as the most commonly detected strain in human brucellosis cases. These strains were mainly clustered in Inner Mongolia and Shannxi Province (75.7%), limiting the generalizability of the results to other provinces. Live cattle movement or trade was identified as the key factor driving brucellosis transmission, but its transmission pattern remains unknown within the Chinese dairy sector. These knowledge gaps require a more effective One Health approach to be bridged. A coordinated and evidence-based research program is essential to inform regional or national control strategies that are both feasible and economical in the Chinese context.

Influence of Varied Environment Conditions on the Gut Microbiota of Yaks

Despite the crucial role of the gut microbiota in different physiological processes occurring in the animal body, reports regarding the gut microbiota of animals residing in different environmental conditions like high altitude and different climate settings are limited. The Qinghai-Tibetan Plateau is renowned for its extreme climatic conditions that provide an ideal environment for exploring the effects of high altitude and temperature on the microbiota of animals. Yaks have unique oxygen delivery systems and genes related to hypoxic response. Damxung, Nyêmo, and Linzhou counties in Tibet have variable altitudes and temperatures that offer distinct settings for studying yak adaptation to elevated terrains. The results of our study suggest that amplicon sequencing of V3-V4 and internal transcribed spacer 2 (ITS2) regions yielded 13,683 bacterial and 1912 fungal amplicon sequence variants (ASVs). Alpha and beta diversity indicated distinct microbial structures. Dominant bacterial phyla were Firmicutes, Bacteroidota, and Actinobacteriota. Genera UCG-005, Christensenellaceae_R-7_group, and Rikenellaceae_RC9_gut_group were dominant in confined yaks living in Damxung county (DXS) and yaks living in Linzhou county (LZS), whereas UCG-005 prevailed in confined yaks living in Nyêmo county (NMS). The linear discriminant analysis effect size (LEfSe) analysis highlighted genus-level differences. Meta-stat analysis revealed significant shifts in bacterial and fungal community composition in yaks at different high altitudes and temperatures. Bacterial taxonomic analysis revealed that two phyla and 32 genera differed significantly (p < 0.05). Fungal taxonomic analysis revealed that three phyla and four genera differed significantly (p < 0.05). Functional predictions indicated altered metabolic functions, especially in the digestive system of yaks living in NMS. This study reveals significant shifts in yak gut microbiota in response to varying environmental factors, such as altitude and temperature, shedding light on previously unexplored aspects of yak physiology in extreme environments.

Brucellae as resilient intracellular pathogens: epidemiology, host-pathogen interaction, recent genomics and proteomics approaches, and future perspectives

Brucellosis is considered one of the most hazardous zoonotic diseases all over the world. It causes formidable economic losses in developed and developing countries. Despite the significant attempts to get rid of Brucella pathogens in many parts of the world, the disease continues to spread widely. Recently, many attempts proved to be effective for the prevention and control of highly contagious bovine brucellosis, which could be followed by others to achieve a prosperous future without rampant Brucella pathogens. In this study, the updated view for worldwide Brucella distribution, possible predisposing factors for emerging Brucella pathogens, immune response and different types of Brucella vaccines, genomics and proteomics approaches incorporated recently in the field of brucellosis, and future perspectives for prevention and control of bovine brucellosis have been discussed comprehensively. So, the current study will be used as a guide for researchers in planning their future work, which will pave the way for a new world without these highly contagious pathogens that have been infecting and threatening the health of humans and terrestrial animals.

Approaches for disease prioritization and decision-making in animal health, 2000-2021: a structured scoping review

This scoping review identifies and describes the methods used to prioritize diseases for resource allocation across disease control, surveillance, and research and the methods used generally in decision-making on animal health policy. Three electronic databases (Medline/PubMed, Embase, and CAB Abstracts) were searched for articles from 2000 to 2021. Searches identified 6, 395 articles after de-duplication, with an additional 64 articles added manually. A total of 6, 460 articles were imported to online document review management software (sysrev.com) for screening. Based on inclusion and exclusion criteria, 532 articles passed the first screening, and after a second round of screening, 336 articles were recommended for full review. A total of 40 articles were removed after data extraction. Another 11 articles were added, having been obtained from cross-citations of already identified articles, providing a total of 307 articles to be considered in the scoping review. The results show that the main methods used for disease prioritization were based on economic analysis, multi-criteria evaluation, risk assessment, simple ranking, spatial risk mapping, and simulation modeling. Disease prioritization was performed to aid in decision-making related to various categories: (1) disease control, prevention, or eradication strategies, (2) general organizational strategy, (3) identification of high-risk areas or populations, (4) assessment of risk of disease introduction or occurrence, (5) disease surveillance, and (6) research priority setting. Of the articles included in data extraction, 50.5% had a national focus, 12.3% were local, 11.9% were regional, 6.5% were sub-national, and 3.9% were global. In 15.2% of the articles, the geographic focus was not specified. The scoping review revealed the lack of comprehensive, integrated, and mutually compatible approaches to disease prioritization and decision support tools for animal health. We recommend that future studies should focus on creating comprehensive and harmonized frameworks describing methods for disease prioritization and decision-making tools in animal health.

A systematic review of economic assessments for brucellosis control interventions in livestock populations

Brucellosis in livestock is a disease of paramount importance to animal and human health authorities due to its socio-economic and public health consequences. Benefit cost analyses can help policymakers decide whether allocation of resources is economically beneficial to cover the costs of brucellosis control interventions in populations. One broad question of interest is: what are the consequences of acting, or failing to act, on policy options of selected intervention scenarios (e.g., vaccination, test-and-slaughter, vaccination combined with test-and-slaughter, versus a status-quo scenario). The objective of the systematic review reported here was to conduct a critical appraisal of published research reports of economic assessments of brucellosis control interventions in livestock populations. The systematic review followed standard guidelines using a Population, Intervention, Comparison, Outcome, and Context framework and Preferred Reporting Items for Systematic Review and Meta-Analysis. The review targeted research reports focused on brucellosis control interventions in livestock populations at the national or regional level. Economic outcomes of interest were benefit-cost ratio (BCR), net present value, internal rate of return, or payback period. Eleven studies conducted in Brazil, China, India, Iraq, Mexico, Mongolia, Spain, Turkey, or the USA met the inclusion criteria and were included. The baseline prevalence of brucellosis in selected study populations ranged from 1.4% in cattle in Turkey to 20% in goats in Mexico. In six studies, selected intervention scenarios of vaccination alone produced BCRs that ranged from 3.2 in yaks in China or in cattle, sheep and goats in Mongolia, to 21.3 in cattle and/or buffalo in India. In three studies, interventions of test-and-slaughter produced BCRs that ranged from - 1.2 in goats in Mexico to 0.6 in cattle in Spain. In four studies, vaccination in combination with test-and-slaughter produced BCRs that ranged from 0.2 in yaks in China to 3.7 in cattle and buffalo in India. In seven studies, using sensitivity analysis, different input parameters (prevalence of brucellosis, meat price, cashmere price, vaccination coverage, test-and-slaughter coverage, milk price, vaccination protection, abortion cost, abortion rate, or price of lamb) had an impact on economic outcomes. Vaccination alone was cost-effective, but test-and-slaughter was not, for brucellosis control in selected livestock populations in focus countries. Vaccination in combination with test-and-slaughter produced profitable or nonprofitable economic outcomes. While most studies reported the cost and benefits of implementing brucellosis control interventions, only one study explained socio-economic consequences of economic outcomes, when acting, or failing to act, on selected interventions in livestock populations.

Brucellosis prevalence in yaks in China in 1980-2019: A systematic review and meta-analysis

In the Qinghai-Tibet Plateau of China, the yak is an animal of particular economic interest, which provides protein and income for herders in daily life. Brucellosis is a bacterial disease that can infect humans and animals, including yaks. It can damage the yak reproductive system, causing miscarriage and orchitis. At the same time, brucellosis threatens the health of herders. We performed this meta-analysis using R software to explore the combined prevalence and risk factors of brucellosis in yak in China. Variability was assessed by the I² statistic and Cochran Q statistic. We identified 52 publications of related research from four databases (Wanfang Data, VIP Chinese Journal Database, China National Knowledge Infrastructure, and of PubMed). The pooled prevalence of yak brucellosis was 8.39 %. Prevalence was highest in Southwestern China (11.1 %). The point estimate of brucellosis in yak from 2012 to 2016 was the highest (11.47 %). The point estimate of age ≤ 12 months (1.44 %) was lower than that of age > 12 months (15.6 %). This study shows that yak brucellosis is serious, and its incidence is higher than before 2012. We recommend carrying out large-scale yak brucellosis investigations in Western China and conducting comprehensive testing planning. The detection of brucellosis in adult animals should be strengthened to reduce the economic loss caused by brucellosis to herders and to improve public health.

An epidemiological study of brucellosis on mainland China during 2004-2018

Brucellosis has re-emerged in China in recent years, resulting in an increasing health burden and economic losses for humans and the livestock industries. This study integrated data from human and livestock brucellosis surveillance systems to explore the changing epidemiology of brucellosis from 2004 to 2018 in China. A total of 524,980 human cases of brucellosis were reported, with the average annual incidence in humans being significantly higher for the period 2012-2018 than for 2004-2011 (3.3 vs. 1.9 per 100,000 residents). An autoregressive integrated moving average (ARIMA) model predicted an upward trend in the monthly incidence of brucellosis in humans in 2019 and 2020. Characteristics including being male, aged 45-54 years, working in the livestock industries, and residing in the northern provinces of China increased the risk of people contracting brucellosis. The percentage of provinces with infected people increased from 67.7% (21/31) in 2004 to all provinces in 2018. A total of 29,115 outbreaks were reported in livestock from 2004 to 2018, with 443,883 seropositive animals although only 381,224 (85.9%) of these were culled. The monthly incidence of brucellosis in humans was strongly positively correlated (r = .539, p < .001) with the number of outbreaks of brucellosis in livestock reported 3 months prior to the human cases. At the provincial level, the annual incidence of brucellosis in humans was significantly positively correlated with the sheep population (r = .786, p < .01). In conclusion, brucellosis in humans and livestock has been spreading in mainland China in the past decade. A more active surveillance of brucellosis in both livestock and humans in China should be coordinated and adjusted by adopting an evidence-based 'One Health' approach, particularly in high-risk regions and livestock industries.

Human brucellosis epidemiology in the pastoral area of Hulun Buir city, Inner Mongolia autonomous region, China, between 2003 and 2018

Human brucellosis represents a serious public health concern in Hulun Buir and requires a comprehensive epidemiologic analysis to define adapted control measures. The present study describes the case numbers, constituent ratios and incidence rate of human brucellosis. Conventional biotyping, that is abortus, melitensis, ovis and suis (AMOS)-PCR and multi-locus variable-number tandem repeat analysis (MLVA) were used to characterize the Brucella strains. Between 2003 and 2018, a total of 23,897 human brucellosis cases were reported, with an incidence rate of 56.03/100,000, which is 20 times higher than the country's average incidence. This incidence rate increased year after year, culminating in 2005 and decreased between 2011 and 2018. Because Hulun Buir relies on a nomadic livestock rearing system, brucellosis spreads easily among different animal species and humans. In Xin Barag Left Banner and Xin Barag Right Banner, the incidence rates were, respectively, 226.54/100,000 and 199.10/100,000, exceeding those observed in other areas. Most of the cases occurred in the 25- to 45-year-old group, accounting for 65.74% of the cases (15,709/23,897), and among farmers, accounting for 66.71% (15,942/23,897). The male to female incidence ratio was 2.67:1. The higher incidence in younger people and the large gender ratio reflected the unique traditional production and lifestyle of nomads. Most reported cases were observed from April to June, indicating that more than 40% of the cases were related to the delivery of domestic livestock. The biotyping showed that the 44 isolated strains were all B. melitensis, including 12 Brucella melitensis biovar (bv) 1 and 32 B. melitensis bv. 3. The strains displayed a genetic similarity of 80%-100%. Our hypothesis is that human brucellosis outbreak in this region may be originating from a limited source of infection, so further investigation is necessary. The epidemic situation of human brucellosis in Hulun Buir is extremely serious, strengthened surveillance and control in animals' brucellosis should be priority.

Brucella: Reservoirs and Niches in Animals and Humans

Brucella is an intracellular bacterium that causes abortion, reproduction failure in livestock and leads to a debilitating flu-like illness with serious chronic complications if untreated in humans. As a successful intracellular pathogen, Brucella has developed strategies to avoid recognition by the immune system of the host and promote its survival and replication. In vivo, Brucellae reside mostly within phagocytes and other cells including trophoblasts, where they establish a preferred replicative niche inside the endoplasmic reticulum. This process is central as it gives Brucella the ability to maintain replicating-surviving cycles for long periods of time, even at low bacterial numbers, in its cellular niches. In this review, we propose that Brucella takes advantage of the environment provided by the cellular niches in which it resides to generate reservoirs and disseminate to other organs. We will discuss how the favored cellular niches for Brucella infection in the host give rise to anatomical reservoirs that may lead to chronic infections or persistence in asymptomatic subjects, and which may be considered as a threat for further contamination. A special emphasis will be put on bone marrow, lymph nodes, reproductive and for the first time adipose tissues, as well as wildlife reservoirs.

Brucella melitensis, a latent "travel bacterium," continual spread and expansion from Northern to Southern China and its relationship to worldwide lineages

Brucellosis caused by Brucella melitensis is considered to be one of the most important zoonotic diseases in China. In this study, Conventional bio-typing, MLVA (multiple locus variable-number tandem repeat analysis), and WGS (whole-genome sequencing)-SNP (single nucleotide polymorphism) were used to study the genetic similarity of B. melitensis in northern and southern China and analyze its relationship with worldwide lineages. Currently, the distribution of species/biovars of B. melitensis has obviously changed, and B. melitensis has become the dominant species in southern regions of China. Strains from the southern had a common geographic origin with strains from the northern. Many MLVA-16 events were shared in the genotypes of the southern and northern strains, suggest that genotypic movement occurred from north to south. Based on WGS-SNP analysis, strains from different provinces were closely related and may have descended from one common ancestor, suggests that the southern strains originated from northern China. These data indicate that B. melitensis is a latent “travel bacterium” that spread and expanded from North China to South China. Moreover, B. melitensis strains from China are also genetically related to strains from other Asian regions (Kazakhstan, Russia, Mongolia, and India). The movement of infected sheep and their products requires control.

Evaluating the effect of TLR4-overexpressing on the transcriptome profile in ovine peripheral blood mononuclear cells

Background

Toll-like receptor 4 (TLR4) plays an important role in the elimination of Gram-negative bacteria infections and the initiation of antiinflammatory response. Using the technology of pronuclear microinjection, genetically modified (GM) sheep with TLR4 overexpression were generated. Previous studies have shown that these GM sheep exhibited a higher inflammatory response to Gram-negative bacteria infection than wild type (WT) sheep. In order to evaluate the gene expression of GM sheep and study the co-expressed and downstream genes for TLR4, peripheral blood mononuclear cells (PBMC) from TLR4-overexpressing (Tg) and wild type (WT) sheep were selected to discover the transcriptomic differences using RNA-Seq.

Result

An average of 18,754 and 19,530 known genes were identified in the Tg and WT libraries, respectively. A total of 338 known genes and 85 novel transcripts were found to be differentially expressed in the two libraries (p < 0.01). A differentially expressed genes (DEGs) enrichment analysis showed that the GO terms of inflammatory response, cell recognition, etc. were significantly (FDR < 0.05) enriched. Furthermore, the above DEGs were significantly (FDR < 0.05) enriched in the sole KEGG pathway of the Phagosome. Real-time PCR showed the OLR1, TLR4 and CD14 genes to be differentially expressed in the two groups, which validated the DEGs data.

Conclusions

The RNA-Seq results revealed that the overexpressed TLR4 in our experiment strengthened the ovine innate immune response by increasing the phagocytosis in PBMC.

Evaluation of a milk ELISA as an alternative to a serum ELISA in the determination of the prevalence and incidence of brucellosis in dairy herds in Hubei Province, China

This study was designed to compare a milk I-ELISA with a serum ELISA for the diagnosis of brucellosis in dairy cattle and then to use the milk I-ELISA to determine the prevalence and incidence of brucellosis in dairy herds in Hubei Province, China. The two tests were shown to have good agreement with a Cohen's kappa statistic of 0.747 (p < 0.001) when 147 animals originating from 4 dairy herds in the province were tested. The results of Bayesian Latent Class Analysis estimated that the sensitivity and specificity of the milk I-ELISA under field conditions were 87.2 % and 92.0 %, respectively. An epidemiological survey based on the milk I-ELISA was then conducted in 3091 cows from 15 commercial dairy herds from January to July 2018 in Hubei Province. The animal level real prevalence varied from 34.9 % (95 % CI: 28.5, 41.8) to 51.4 % (95 % CI: 48.2, 54.6) in the 15 herds tested. Most farms (93.3 %) tested contained at least one test-positive animal. As only ten farms met the inclusion criteria for the calculation of incidence risk, the overall real incidence risk in 10 of these farms was 0.4 % (95 % CI: 0.1, 1.2) per 3 months, which highlights the potential for spread of the disease within infected herds. It is concluded that the milk I-ELISA test could be used as a rapid screening test for brucellosis in unvaccinated dairy cows and, given the high occurrence of bovine brucellosis in this study, an effective prevention and control program needs to be developed and implemented in Hubei Province, China.

First identification of a Brucella abortus biovar 4 strain from yak in Tibet, China

Brucellosis is one of the major zoonotic diseases in the world. In China, understanding on its causative agent Brucella is still limited. Recently, we isolated a Brucella strain XZ19-1 from yak in Lhasa, Tibet. Phenotypical characterization proved that it belongs to B. abortus biovar 4, a biotype that has never been reported in China. MLVA-16 genotyping revealed a novel profile (4-5-3-12-2-2-3-3-8-32-8-5-4-3-3-3) in this strain, while MLST sequence typing demonstrated that it belongs to ST 71. Furthermore, the whole genome of XZ19-1 strain was sequenced. Subsequent phylogenetic analysis demonstrated that XZ19-1was genetically more closely related to B. abortus strains originated from European countries rather than to those collected from China previously. Isolation and identification of XZ19-1 strain may thus indicate a unique Brucella lineage existing in Qing-Tibet plateau. These findings will help to improve the diagnosis and epidemiological studies of brucellosis in animals and human in this part of China.

Socio-economic impacts of brucellosis on livestock production and reproduction performance in Koibatek and Marigat regions, Baringo County, Kenya

Background

Brucellosis in Africa is caused by Brucella species transmitted through contaminated or contacts with infected animals or their carcasses. The disease reduces livestock production and reproduction performance evident by frequent episodes of abortion, still births, swollen testes, weak calves/lambs and swollen joints. However, the socio-economic impacts of these brucellosis-associated symptoms on milk, fat, meat and blood production, infertility, sale value, dowry and costs of treatment has not been evaluated extensively in developing countries. In Baringo County, Kenya, there is a continuous movement of cattle as a result of trade and grazing, which predisposes many herds to brucellosis infection. The objective of this study was to investigate the socio-economic impacts of Brucella infection on production systems for sheep, goats, cattle and camels and explore the impact of brucellosis on livestock production and reproduction performance among livestock keeping communities in Baringo County, Kenya. The study adopted a cross-sectional survey using quantitative data collection methods.

Results

Results demonstrated an impact on milk production in suspected brucellosis cases resulting from abortions (OR = 0.151, P < 0.0001) and swollen joints (OR = 2.881, P < 0.0001). In terms of infertility, abortion as a symptom of brucellosis (OR = 0.440, P = 0.002), still birth (OR = 0.628, P = 0.042), and weak calf or lamb (OR = 0.525, P = 0.005) had an impact on infertility. In terms of sale value, abortion (OR = 0.385, P = 0.008), weak calf/lamb (OR = 2.963, P = 0.013) had an impact on sale value. Other analyses demonstrated that for dowry, swollen testes (OR = 5.351, P = 0.032), weak calf and lambs (OR = 0.364, P = 0.019) had a likelihood of reduction of dowry value. Finally, in terms of cost of treatment, abortion (OR = 0.449, P = 0.001), still births (OR = 0.208, P = 0.015), swollen testes (OR = 0.78, P = 0.014), weak calf/lambs (OR = 0.178, P = 0.007) and swollen joints (OR = 0.217, P = 0.003) significantly increased the costs of treatments. There was no impact on fat and meat and blood production.

Conclusion

Even though there was a huge socio-economic impact on milk production, infertility, sale value, and dowry, it was the costs of treatment that was significantly impacted on all symptoms associated with brucellosis on this community. A ‘One Health’ approach in tackling the brucellosis menace as a holistic approach is recommended for both humans and their livestock.