Brucellosis in Ethiopia: A comprehensive review of literature from the year 2000-2020 and the way forward

Long ignored but making a comeback: a worldwide epidemiological evolution of human brucellosis

Brucellosis is a commonly neglected zoonosis that remains a serious global public health concern. The epidemiological evolution of human brucellosis has considerably changed over the past few decades, and epidemic geography is continuously expanding. Human brucellosis is emerging and re-emerging, and is imported from areas where it is endemic due to travel, immigration, and international trade. The disease continues to be prevalent in Asia and Africa, including West Asia, Central Asia, North Africa, and East Africa, with the highest incidence in Syria, Kyrgyzstan, Mongolia, Iran, Algeria, and Kenya. Re-emerging cases are frequently recorded in places where brucellosis has been controlled, such as Bosnia, Herzegovina, Azerbaijan, and the USA. In countries with a high disease burden, disease control and eradication have been extremely difficult because of livestock farming being the only source of livelihood, unique religious beliefs regarding animals, nomadic lifestyle, and low socioeconomic levels. Interventions focused on protecting livestock keepers are needed, particularly for those assisting with goat and sheep births and the consumption of raw dairy products. Notably, in most countries with a high disease burden, each period of several years with a low incidence rate was followed by a subsequent increase in cases, highlighting the necessity of continuous investment and surveillance. In addition, advocacy for the inclusion of brucellosis as a globally mandated reported disease, strict restrictions on animal movement, mandated consumption of pasteurized milk, and health education are needed. This study will help form an evidence-based strategy for international organizations to curb the future spread of brucellosis.

Seroprevalence of brucellosis and associated risk factors in camels and its herders in selected districts of Somali Pastoral Region, Eastern Ethiopia

Brucellosis poses a major public and animal health problem in many parts of the world, particularly in pastoral settings, however, seroepidemological studies are scarce. A cross-sectional study was conducted from December 2021 to April 2022 to estimate the prevalence of brucellosis and to identify the associated risk factors for camels and occupational individuals from three purposively selected districts of the Somali pastoral region in Eastern Ethiopia. Serum samples were serially diluted using the Rose Bengal Plate Test (RBPT) as a screening test and a competitive Enzyme-Linked Immunosorbent Assay (cELISA) test as a confirmatory test. From a total of 450 camels and 250 human serum samples tested, the overall seroprevalence was confirmed to be 2.9 % (95 % CI, 1.5-4.9) in camels and 2.0 % (95 % CI, 0.2-3.7) in humans. In camels, abortion and retained fetal membrane (RFM) were significant risk factors for Brucella seropositivity (p<0.05). However, in humans, RFM disposal differed significantly (p<0.05). The fact that brucellosis is found in both camels and humans highlights the importance of implementing a coordinated One Health approach to control and eliminate the disease. This would ensure improved public health and increased livestock productivity.

Sero-epidemiological study of brucellosis in cattle under pastoral/agro-pastoral and mixed crop-livestock systems in South Omo, southern Ethiopia

Background

In the pastoral/agro-pastoral communities in Ethiopia, like in South Omo, brucellosis constitutes a serious health threat for livestock and the public. The public health risk is especially high in these communities, as their way of life is highly linked with their herds.

Objective

The study was conducted to estimate the seroprevalence and identify potential risk factors of cattle brucellosis in South Omo zone in southern Ethiopia.

Methods

A total of 614 traditionally managed local zebu female cattle, above six months old, were bled and data on hypothesized risk factors were collected using a semi-structured questionnaire. The preliminary screening of the sera for Brucella antibodies was done using Rose Bengal Plate Test (RBPT) and positive sera were further subjected to complement fixation test (CFT).

Results

The overall animal level seroprevalence of brucellosis was 2.8 % (95 % CI: 1.72-4.41) while herd level prevalence was 11.3 % (95 % CI: 6.5-19.0). Among the risk factors considered, seroprevalence was associated with herd size, new animal introduction, district, history of occurrence of abortion, and retained fetal membranes (RFM), at both individual- and herd-level (p < 0.05). Higher seroprevalence of brucellosis was observed in cows than heifers and in animals older than 4 years (p < 0.05). Brucella seroprevalence was higher in herds in lowland areas than those in mid-altitude and highlands (p < 0.05).

Conclusion

The individual and herd level prevalence observed in our study indicates endemicity of brucellosis and the potential public health threat it poses in pastoral and agro-pastoral areas of southern Ethiopia. The results of the study also suggest that the disease might be responsible for significant losses in cattle productivity due to impaired reproductive performance.

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.

Spatiotemporal dynamics and influencing factors of human brucellosis in Mainland China from 2005-2021

BACKGROUND

Brucellosis poses a significant public health concern. This study explores the spatial and temporal dynamic evolution of human brucellosis in China and analyses the spatial heterogeneity of the influencing factors related to the incidence of human brucellosis at the provincial level.

METHODS

The Join-point model, centre of gravity migration model and spatial autocorrelation analysis were employed to evaluate potential changes in the spatial and temporal distribution of human brucellosis in mainland China from 2005 to 2021. Ordinary Least Squares (OLS), Geographically Weighted Regression (GWR), and Multi-scale Geographically Weighted Regression (MGWR) models were constructed to analyze the spatial and temporal correlation between the incidence rate of human brucellosis and meteorological and social factors.

RESULTS

From 2005 to 2021, human brucellosis in China showed a consistent upward trend. The incidence rate rose more rapidly in South, Central, and Southwest China, leading to a shift in the center of gravity from the North to the Southwest, as illustrated in the migration trajectory diagram. Strong spatial aggregation was observed. The MGWR model outperformed others. Spatio-temporal plots indicated that lower mean annual temperatures and increased beef, mutton, and milk production significantly correlated with higher brucellosis incidence. Cities like Guangxi and Guangdong were more affected by low temperatures, while Xinjiang and Tibet were influenced more by beef and milk production. Inner Mongolia and Heilongjiang were more affected by mutton production. Importantly, an increase in regional GDP and health expenditure exerted a notable protective effect against human brucellosis incidence.

CONCLUSIONS

Human brucellosis remains a pervasive challenge. Meteorological and social factors significantly influence its incidence in a spatiotemporally specific manner. Tailored prevention strategies should be region-specific, providing valuable insights for effective brucellosis control measures.

Familial brucellosis osteoarthritis: A report of two patients

Brucellosis is a zoonotic infectious disease caused by brucella infection, which is a natural epidemic disease that infects humans and animals such as cattle, sheep, pigs, and dogs. Clinically, it is mainly manifested as fever, excessive sweating, joint pain and swollen liver, spleen and lymph nodes of different diseases. We report two cases of brucellosis in a family living in China. They both developed brucellosis osteoarthritis, with a 39-year-old man in the left elbow and a 68-year-old woman presenting with brucellosis spondylitis. They were well treated with doxycycline and rifampicin. Investigating a common source found that the family raised goats.

Whole genome sequencing of Ethiopian Brucella abortus isolates expands the known diversity of an early branching sub-Saharan African lineage

Brucellosis remains one of the most significant zoonotic diseases globally, responsible for both considerable human morbidity and economic losses due to its impacts on livestock productivity. Despite this, there remain significant evidence gaps in many low- and middle-income countries, including those of sub-Saharan Africa. Here we report the first molecular characterisation of Brucella sp. from Ethiopia. Fifteen Brucella sp. isolates from an outbreak in cattle from a herd in central Ethiopia were identified as Brucella abortus, using bacterial culture and molecular methods. Sequencing of the Ethiopian B. abortus isolates allowed their phylogenetic comparison with 411 B. abortus strains of diverse geographical origins, using whole genome single nucleotide polymorphisms (wgSNP). The Ethiopian isolates belonged to an early-branching lineage (Lineage A) previously only represented by data from two strains, both of sub-Saharan African origin (Kenya and Mozambique). A second B. abortus lineage (Lineage B), also comprised solely of strains originating from sub-Saharan Africa, was identified. The majority of strains belonged to one of two lineages of strains originating from a much broader geographical range. Further analyses based on multi-locus sequence typing (MLST) and multi-locus variable-number tandem repeat analysis (MLVA) expanded the number of B. abortus strains available for comparison with the Ethiopian isolates and were consistent with the findings from wgSNP analysis. MLST profiles of the Ethiopian isolates expanded the sequence type (ST) diversity of the early branching lineage of B. abortus, equivalent to wgSNP Lineage A. A more diverse cluster of STs, equivalent to wgSNP Lineage B, was comprised solely of strains originating from sub-Saharan Africa. Similarly, analysis of B. abortus MLVA profiles (n = 1891) confirmed that the Ethiopian isolates formed a unique cluster, similar to only two existing strains, and distinct from the majority of other strains of sub-Saharan African origin. These findings expand the known diversity of an under-represented lineage of B. abortus and suggest a potential evolutionary origin for the species in East Africa. In addition to providing information concerning Brucella species extant within Ethiopia this work serves as the basis for further studies on the global population structure and evolutionary history of a major zoonotic pathogen.