Isolation and identification of Brucella melitensis using bacteriological and molecular tools from aborted goats in the Afar region of north-eastern Ethiopia

Seroprevalence of Brucellosis in Sheep and Goats With Owners' Knowledge, Attitudes and Practices in Garowe District, Nugal region, Somalia

Brucellosis is an important neglected bacterial zoonotic disease in sub-Saharan Africa, including Somalia. A cross-sectional study was conducted in the Garowe district, Nugal region, Somalia, from May 2022 to January 2023 to estimate the seroprevalence of small ruminant brucellosis and assess owners' knowledge, attitudes, and practices toward brucellosis. A total of 384 sheep and goats were selected using a simple random sampling technique and screened for Brucella antibodies by the Modified Rose Bengal Plate Test, and positive samples were then further confirmed using an indirect enzyme-linked immunosorbent assay. For the questionnaire survey, 384 households were selected randomly, and a structured questionnaire was used to assess owners' knowledge, attitudes, and practices toward brucellosis. The overall brucellosis seroprevalence was 4.7% in small ruminants (95% CI: 2.8-7.3), and the true seroprevalence was calculated as 5.2%. According to the multivariable logistic regression analysis, sex was found to be a potential risk factor for small ruminant brucellosis (P < .05). More specifically, female sheep and goats were 9.13 times (aOR 9.13, 95% CI: 1.18-70.33) more likely to become seropositive than males. The owners' knowledge, attitudes, and practices toward brucellosis were found to be low, and education level was associated with owners' knowledge (χ2 = 16.78; P < .001), attitudes (χ2 = 19.4; P < .001) and practices (χ2 = 34.0; P < .001). There is also a significant association between owner knowledge, attitudes, and practices and seropositivity of brucellosis in sheep and goats. Moderate seroprevalence, together with insufficient knowledge, attitudes, and practices of owners, makes brucellosis a threat to animals and the entire community. Hence, raising community awareness of the disease is essential to reduce the impact on small ruminant productivity and the risks to public health.

Seroprevalence of small ruminant brucellosis and owners knowledge, attitude and practices in Chiro and Burka Dhintu Districts, West Hararghe, Ethiopia

Brucellosis is one of zoonotic bacterial diseases with significant veterinary and public health consequences in sub-Saharan African countries, including Ethiopia. A cross-sectional study design was conducted with the objective of estimating the seroprevalence of small ruminant brucellosis and assessing owners' knowledge, attitude and practices (KAP) on brucellosis in Chiro and Burka Dhintu Districts in Eastern Ethiopia. A total sample of 444 animals were taken using a cluster based multistage sampling technique. Screening for Brucella antibodies and confirmation of positive test results were conducted using Modified Rose Bengal Plate Test (MRBPT) and indirect enzyme-linked immunosorbent assay (I-ELISA) respectively. For the questionnaire survey, 444 randomly selected sheep and goat owners were interviewed using a pretested structured questionnaire. The overall seroprevalence of small ruminant brucellosis was found to be 6.5 % (95 % CI: 4.6-9.3). The multivariable logistic regression analysis identified sex and age as potential risk factors (P < 0.05). More specifically, females were 3.4 times (AOR = 3.4, 95 % CI: 1.2-9.2) more likely to become seropositive than their counterparts, and the odds of seropositivity in adult sheep and goats was 5.6 times (AOR = 5.6, 95 % CI: 1.3-24.7) higher than that of young animals. The knowledge, attitude and practices of animal owners with regard to brucellosis were low, and the level of education was independently associated with the owners' knowledge and attitude. Moderate seroprevalence, combined with inadequate knowledge, attitudes, and practices of animal owners, makes small ruminant brucellosis a threat to animals and the entire community. Hence, strengthening veterinary services and raising community awareness about the disease is essential to reduce the impact on small ruminant productivity and minimize the risks to public health.

Molecular detection of Brucella species among aborted small ruminants in southeast Iran

Brucellosis, caused by Brucella bacteria, is a common zoonotic infectious disease with various clinical manifestations in humans and animals. The disease is endemic in human and ruminant populations in Iran, with a particular prevalence in areas where humans have close interactions with livestock. Since domestic animals serve as the primary reservoir for brucellosis, this study aimed to identify the presence of Brucella spp. among aborted small ruminants in southeast Iran. Between 2021 and 2022, aborted fetuses of small ruminants (46 sheep and 4 goats) were collected from Zarand County in the Kerman province. Swab samples from the abomasum contents of these fetuses were obtained and subjected to DNA extraction. The samples were then tested for Brucella spp. detection using the polymerase chain reaction (PCR) method. Out of the 50 aborted fetuses examined, Brucella spp. was detected in 15 (30%) specimens, comprising 13 (28%) sheep and 2 (50%) goats. Species typing revealed the presence of Brucella ovis (6 sheep and 1 goat), Brucella melitensis (6 sheep), and Brucella abortus (1 sheep) among the positive specimens. This cross-sectional study highlights the high prevalence of various Brucella species in samples from small ruminant abortions in southeast Iran. Additionally, the identified Brucella species were not limited to their primary host livestock. These indicated potential cross-species transmission among small ruminants.

Polyphasic Characterization of Brucella spp. in Livestock Slaughtered from Abattoirs in Eastern Cape, South Africa

In livestock, brucellosis is mainly an asymptomatic disease except when abortion occurs; therefore, two serological tests are used for diagnosis as no single test is suitable. Abattoir samples enable a combination of culture, molecular, and serological tests to detect brucellosis. This study assessed Brucella-specific PCR (ITS-PCR) to detect brucellosis and to conduct a molecular characterization of Brucella spp. isolated from PCR-positive livestock (n = 565) slaughtered at abattoirs and the appropriate sample tissue(s). ITS-PCR detected Brucella DNA in 33.6% of cattle, 14.5% of sheep, and 4.7% of pig tissues. Impure Brucella cultures from PCR-positive tissues were 43.6% (44/94) of cattle, 51.7% (15/29) of sheep, and 50% (2/4) of pigs with predominantly B. abortus identification with AMOS-PCR and low isolation of mixed B. abortus and B. melitensis in all species. In cattle, 33% of isolates were from lymph nodes, while in sheep 38.0% were from the liver and kidney and only from tonsils in pigs (2/4). Brucella infections identified with AMOS-PCR were present in seropositive and mainly seronegative (75.6-100%) livestock with the potential to cause brucellosis during pregnancy or breeding. This study demonstrated the value of the polyphasic approach, especially with chronic infections and the potential risk of these asymptomatic animals.

Study on small ruminant brucellosis and owners awareness in two selected districts of southern region, Ethiopia

INTRODUCTION

Brucellosis is one of the infectious diseases that has the greatest impact on the productivity of sheep and goats. A cross-sectional study followed by a simple random sampling technique was used to investigate the seroprevalence of brucellosis (Rose Bengal plate test; RBPT and complement fixation test; CFT) in small ruminants and its related risk variables from November 2019 to June 2020 in Kolme and Abala Abaya districts. A questionnaire was also given to owners to assess their existing knowledge of the disease.

RESULT

Using the RBPT and CFT, 28 (4.1%) and 23 (3.33%) of the 690 animals were found to be seropositive for brucellosis, respectively. In this study, the seroprevalence of brucellosis detected in the Kolme district (5.3%) was greater when compared to Abala Abaya (1.0%). The odds of Brucella infection were greater for goats (odds ratio [OR] 6.0, 95% confidence interval [CI] 16 0.8-44.9) than for sheep. The odds of adult animals (OR 0.05, 95% CI 0.03-0.07) being positive for brucellosis was higher than young animals. A statistically significant difference in the seropositivity of brucellosis was detected in univariate logistic regression among districts, different age groups, herd size, parity number, and reproductive health problems except for species and sex, but in multivariate logistic regression, only reproductive health problems were revealed a statistically significant difference. Out of 138 families, 100% of respondents were unaware of brucellosis, 94.5% drink raw milk, and 74% handle animals with retained fetal membranes with their bare hands.

CONCLUSION

This study showed that brucellosis was a widely spread disease in the study areas and poses a substantial public health danger. To reduce the spread of the disease in small ruminants, public health risks, and economic losses, stringent vaccination application and awareness of personal hygiene are critical.

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.

Rapid, ultrasensitive, and highly specific identification of Brucella abortus utilizing multiple cross displacement amplification combined with a gold nanoparticles-based lateral flow biosensor

Brucella abortus (B. abortus) as an important infectious agent of bovine brucellosis cannot be ignored, especially in countries/regions dominated by animal husbandry. Thus, the development of an ultrasensitive and highly specific identification technique is an ideal strategy to control the transmission of bovine brucellosis. In this report, a novel detection protocol, which utilizes multiple cross displacement amplification (MCDA) combined with a gold nanoparticles-based lateral flow biosensor (AuNPs-LFB) targeting the BruAb2_0168 gene was successfully devised and established for the identification of B. abortus (termed B. abortus-MCDA-LFB). Ten specific primers containing engineered C1-FAM (carboxyfluorescein) and D1-biotin primers were designed according to the MCDA reaction mechanism. These genomic DNA extracted from various bacterial strains and whole blood samples were used to optimize and evaluate the B. abortus-MCDA-LFB assay. As a result, the optimal reaction conditions for the B. abortus-MCDA-LFB assay were 66°C for 40 min. The limit of detection of the B. abortus-MCDA-LFB was 10 fg/μl (~3 copies/μl) for genomic DNA extracted from pure cultures of B. abortus isolate. Meanwhile, the B. abortus-MCDA-LFB assay accurately identified all tested B. abortus strains, and there was no cross-reaction with non-B. abortus pathogens. Moreover, the detection workflow of the B. abortus-MCDA-LFB assay for whole blood samples can be completed within 70 min, and the cost of a single test is approximately 5.0 USD. Taken together, the B. abortus-MCDA-LFB assay is a visual, fast, ultrasensitive, low-cost, easy-to-operate, and highly specific detection method, which can be used as a rapid identification tool for B. abortus infections.

Isolation and characterisation of Brucella melitensis by bacteriological and molecular methods from livestock in North Cyprus

In this study, the isolation, biotyping and molecular characterisation of Brucella melitensis from cattle, sheep and goats in North Cyprus are reported on. A total of 319 raw milk samples obtained from seropositive dairy livestock (190 cattle, 74 sheep and 55 goats) and tissue samples including the liver, spleen and abomasal contents obtained from 32 aborted foetal samples (5 cattle, 18 sheep and 9 goats) were analysed for the presence and characterisation of the agent. B. melitensis was isolated and identified from 90 out of 319 (28.2%) milk and 19 out of 32 (59.4%) foetal samples by conventional bacteriological methods. Identification of all 109 isolates was confirmed by using real-time PCR with genus and species-specific primers. Following the preliminary identification, 27 selected isolates representing various counties and herds were further analysed by conventional methods. Twenty (74.1%) isolates were identified as B. melitensis biovar 1 and seven (25.9%) were identified as B. melitensis biovar 3. The Bruce-ladder multiplex PCR assay revealed that all the isolates were field strains. The results of the present study confirmed the presence of B. melitensis in livestock including the cattle population in North Cyprus. Even though the majority of the samples came from seropositive cattle, Brucella abortus was not isolated in the study. The results also revealed the potential public health risk of brucellosis in livestock emphasising the need of implementing strict control and eradication strategies against the disease in animal populations in order to protect human health.

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

Brucellosis is a zoonotic disease of considerable economic and public health significance globally. Despite the limited bacteriological evidence, a large number of serological works revealed that it is prevalent both in livestock and humans in Ethiopia. The current comprehensive review was carried out to provide apparent pooled seroprevalence (APS) estimates at individual animal and herd levels in livestock, and identify factors causing variability between studies conducted over the last two decades, show the spatial distribution, as well as summarizes Brucella species reported from livestock. It also provides APS of brucellosis in humans and evaluates the public health awareness of zoonotic brucellosis. In this review, systematic and synthetic review approaches were followed to summarize the available information. For the systematic review and meta-analysis, articles were selected based on predefined criteria. Data extracted from these articles were analyzed using meta-analytical approaches to provide APS estimates and in-between study variations for humans and all livestock species considered. Sensitivity analyses and bias assessments were conducted using influence plot analysis and, Egger's and Begg's statistics along with funnel plots, respectively. Synthetic review approaches were used to summarize data on isolates and public health awareness. Pooled seroprevalence estimate of brucellosis at national level was 2.6% (95% CI, 2.2-3.0) in cattle, 4% (95% CI, 3.1-5.1) in goats, 3% (95% CI, 2.3-3.9) in sheep and 3% (95% CI, 2.4-3.7) in camels. At a herd level, 16.3% (95% CI, 12.9, 20.5) of cattle, 12.1% (7.1, 19.9) of goat, 13.3% (7.6, 22.1) of sheep and 19.7% (13.8, 27.4) of camel herds in the country had at least one seropositive animal. Cattle in the pastoral/agropastoral production systems had significantly higher (p < 0.05) APS compared to mixed crop-livestock and urban/peri-urban dairy production systems. Pooled seroprevalence of brucellosis in small ruminants (8.3%, 95% CI, 6.3, 10.8) and camels (4.4%, 95% CI, 3.5, 5.6) in Afar were significantly higher (p<0.05) than in other regions. Reports conducted using ELISA and serial Rose Bengal plate test (RBPT)-ELISA had higher (p<0.05) APS estimates than serial RBPT and complement fixation test. Brucella melitensis and B. abortus were reported from goats and cattle, respectively, from three available reports. The APS of brucellosis in humans was 5% (95% CI: 3.3, 7.3). Public awareness of brucellosis was low (18.4%), while, practices that expose humans to Brucella infection were high. Scenario-based control interventions on regions and production systems using one health approach are suggested. This article is protected by copyright. All rights reserved.

Herd-level contamination of Neospora caninum, Toxoplasma gondii and Brucella in milk of Iranian dairy farms

The bulk milk examination is a reliable screening tool for monitoring the quality of milk in the farms. The infection to Neospora caninum, Toxoplasma gondii and Brucella sp. Was evaluated in bulk milk samples of dairy farms in Hamedan province, West part of Iran. All the dairy farms (n = 149) were examined for N. caninum, T. gondii and Brucella infections using milk ring test (MRT), microbiology, serology (Enzyme-linked Immunosorbent Assay), and molecular techniques. Based on molecular methods, Brucella-infection was negative in all farms; while, 55 %, 5.4 % and 2.7 % of samples were positive for N. caninum, T. gondii and mix infection, respectively. The highest Neospora-infection was detected in the farms with history of abortion in fall and winter. There was significant association between Neospora-infection and the presence of dogs and rodents in the farms, herd size, and age of the animals. Also, a significant association was seen between Toxoplasma-infection and the presence of cats and rodents in the farms, as well as age of the animals. Average total bacterial count (TBC) was calculated 1.14 × 10⁶±1.1 × 10⁶. The highest TBC was in the farms from Central locations of studied area (5.7 × 10⁶±2.24 × 10⁶), farms with more than 120 animals (7.9 × 10⁶±2.8 × 10⁶), and farms with ≥50-months age (1.74 × 10⁶±6.3 × 10⁵) in spring and summer (6.9 × 10⁶±3.7 × 10⁶). The number of somatic cells was estimated between 1 × 10⁴ and 2 × 10⁶ (Average = 4.2 × 10⁵±3.39 × 10⁵). The current study was a comprehensive evaluation of Neospora, Toxoplasma and Brucella infections in milk samples of Iranian dairy farms for the first time. Neospora-infection is responsible for economic losses in the region. Health education and milk pasteurization are so helpful for inhibiting the milk borne diseases. To reduce the risk factors, predict and design the appropriate schemes like redundant of heterogeneous animals are recommended.

Integrated human-animal sero-surveillance of Brucellosis in the pastoral Afar and Somali regions of Ethiopia

Background

Brucellosis is widespread in Ethiopia with variable reported prevalence depending on the geographical area, husbandry practices and animal species. However, there is limited information on the disease prevalence amongst pastoral communities, whose life is intricately linked with their livestock.

Methodology

We conducted an integrated human-animal brucellosis sero-surveillance study in two adjacent pastoral regions, Afar and Somali region (SRS). This cross-sectional study included 13 woredas (districts) and 650 households. Blood samples were collected from people and livestock species (cattle, camel, goats and sheep). Sera were analyzed with C-ELISA for camels and shoats (sheep and goats), with I-ELISA for cattle and IgG ELISA for humans. Descriptive and inferential statistics analyses were performed.

Results

A total of 5469 sera were tested by ELISA. Prevalence of livestock was 9.0% in Afar and 8.6% in SRS (ranging from 0.6 to 20.2% at woreda level). In humans, prevalence was 48.3% in Afar and 34.9% in SRS (ranging from 0.0 to 74.5% at woreda level). 68.4% of all households in Afar and 57.5% of households in SRS had at least one animal reactor. Overall, 4.1% of animals had a history of abortion. The proportion of animals with abortion history was higher in seropositive animals than in seronegative animals. Risk factor analysis showed that female animals were significantly at higher risk of being reactors (p = 0.013). Among the species, cattle had the least risk of being reactors (p = 0.014). In humans, there was a clear regional association of disease prevalence (p = 0.002). The older the people, the highest the odds of being seropositive.

Conclusion

Brucellosis is widespread in humans and animals in pastoral communities of Afar and SRS with the existence of geographical hotspots. No clear association was seen between human and particular livestock species prevalence, hence there was no indication as whether B. abortus or B. melitensis are circulating in these areas, which warrants further molecular research prior to embarking on a national control programs. Such programs will need to be tailored to the pastoral context.

Brucellosis is a neglected disease of livestock that can be transmitted to people through consumption of raw animal products and direct contact with animal birth material. Although prevalent in Ethiopia, there is limited information on the disease prevalence amongst pastoral communities, whose life is intricately linked with their livestock. We therefore, conducted a disease surveillance in people and their livestock in Afar and Somali region (SRS), two pastoral regions of Ethiopia. The study included 13 districts and 650 households. A total of 5469 blood samples were collected from people and livestock species (cattle, camel, sheep and goats) and analyzed using commercial brucellosis ELISA assays. Livestock brucellosis prevalence was 9% in Afar and 8.6% in SRS (ranging from 0.6 to 20.2% at woreda level). In humans, prevalence was 48.3% in Afar and 34.9% in SRS (ranging from 0 to 74.5% at woreda level). 68.4% of all households in Afar and 57.5% of households in SRS had at least one positive animal. This study showed that the disease is widespread in human and their livestock in pastoral communities of Afar and SRS with the existence of geographical hotspots. Results will advise on tailored surveillance programs in pastoral communities.

Sero-prevalence and risk factors of Brucella presence in farm bulk milk from open and zero grazing cattle production systems in Rwanda

BACKGROUND

Animal and human brucelloses have been reported in Rwanda, human brucellosis being linked to drinking inadequately heat-treated milk. However, information on Brucella detection and prevalence in milk produced in Rwanda is limited.

OBJECTIVES

To determine the sero-prevalence and risk factors of Brucella in farm bulk milk from zero and open grazing cattle production systems in Rwanda.

METHODS

A total of 330 farm bulk milk samples were collected from 198 zero grazing farms and 132 open grazing farms in a cross-sectional study in Rwanda. Sero-prevalence of Brucella in milk was analysed using indirect enzyme-linked immunosorbent assay. A questionnaire was administered to farmers to determine the risk factors of milk contamination with Brucella.

RESULTS

Anti-Brucella antibodies were prevalent in 19.7% (95% confidence interval (CI), 15.5-24.4) of the 330 collected farm bulk milk. Sero-prevalence was significantly higher (p < 0.05) in open grazing farms (37.9% [50/132]) than in zero grazing farms (7.6% [15/198]). Practising open grazing system (odds ratio, OR = 69.5; 95% CI = 1.6-3033.6), history of abortion (OR = 19.5; 95% CI = 8.1-46.8) and placenta retention (OR = 4.2; 95% CI = 1.7-10.3) were the significant risk factors for the presence of anti-Brucella antibodies in milk.

CONCLUSION

Notably, more than a third of farm bulk milk from open grazing farms in Rwanda contains Brucella antibodies. Considering the zoonotic nature of Brucella, there is a need to reinforce brucellosis control programs in the country.

Brucella Outer Membrane Lipoproteins 19 and 16 Differentially Induce IL-18 Response or Pyroptosis in Human Monocytic Cells

BACKGROUND

Brucella species (B. spp.) are Gram-negative intracellular bacteria, causing severe inflammatory diseases in animals and humans. Two major lipoproteins (L19) and (L16) of Brucella outer membrane proteins (OMPs) were extensively explored in associating with inflammatory response of human monocytes (THP-1).

METHODS

Activated THP-1 cells induced with recombinant L19 and L16 were analyzed in comparison with unlipidated forms (U19 and U16) and lipopolysaccharide (LPS) of B. melitensis, respectively.

RESULTS

Secretion of inflammatory factors TNF-α, IL-6 and IL-1β was significantly increased from L19, L16 or both stimulated THP-1 cells. High secretion of IL-18 was detected only from L19-induced cells. Signaling of those cytokine responses was identified mainly through P38-MAPK pathway, and signaling of L19-induced IL-1β response was partly occurred via NF-κB. Exploration for different forms of IL-18 found that L19-induced production of active IL-18 (18 kD) was through up-regulating NLRP3 and activating caspase-1, while L16-induced production of inactive IL-18 fragments (15 kD and 16 kD) occurred through activating caspase-8/3. Additionally, L19 up-regulated phosphorylation of XIAP for inhibiting caspase-3 activity to cleave IL-18, while L16 activated caspase-3 for producing GSDME-N and leading to pyroptosis of THP-1 cells.

CONCLUSION

Brucella L19 and L16 differentially induce IL-18 response or pyroptosis in THP-1 cells, respectively.

Brucellosis: Prevalence with reference to East African community countries - A rapid review

Brucellosis is a zoonotic disease which is endemic to certain regions of the world including Sub-Saharan Africa. The aim of this article is to provide a recent and rapid review on brucellosis prevalence in East African Community (EAC) countries. Literature was obtained using Google Scholar search engine and screened for relevancy and fulfilment of criteria to 1, 17, 4, 4, 30 and 29 articles retained for brucellosis prevalence in Burundi, Kenya, Rwanda, South Sudan, Tanzania and Uganda. Recent literature (published in the last decade 2010 to 2019) was considered for prevalence results in this review. In EAC, livestock had an animal-level prevalence of 0.2% to 43.8%, 0.0% to 20.0% and 0.0% to 13.8% for cattle, goats and sheep respectively. In humans, the prevalence varied mostly between 0.0% and 35.8%. In conclusion, brucellosis is quite prevalent in the region. The reported prevalence calls for plans or more efforts from individual member countries and from EAC, as a region, to control brucellosis.

Molecular epidemiology of Brucella species in mixed livestock-human ecosystems in Kenya

Brucellosis, caused by several species of the genus Brucella, is a zoonotic disease that affects humans and animal species worldwide. Information on the Brucella species circulating in different hosts in Kenya is largely unknown, thus limiting the adoption of targeted control strategies. This study was conducted in multi-host livestock populations in Kenya to detect the circulating Brucella species and assess evidence of host-pathogen associations. Serum samples were collected from 228 cattle, 162 goats, 158 sheep, 49 camels, and 257 humans from Narok and Marsabit counties in Kenya. Information on age, location and history of abortion or retained placenta were obtained for sampled livestock. Data on age, gender and location of residence were also collected for human participants. All samples were tested using genus level real-time PCR assays with primers specific for IS711 and bcsp31 targets for the detection of Brucella. All genus positive samples (positive for both targets) were further tested with a speciation assay for AlkB and BMEI1162 targets, specific for B. abortus and B. melitensis, respectively. Samples with adequate quantities aggregating to 577 were also tested with the Rose Bengal Test (RBT). A total of 199 (33.3%) livestock and 99 (38.5%) human samples tested positive for genus Brucella. Animal Brucella PCR positive status was positively predicted by RBT positive results (OR = 8.3, 95% CI 4.0-17.1). Humans aged 21-40 years had higher odds (OR = 2.8, 95% CI 1.2-6.6) of being Brucella PCR positive compared to the other age categories. The data on detection of different Brucella species indicates that B. abortus was detected more often in cattle (OR = 2.3, 95% CI 1.1-4.6) and camels (OR = 2.9, 95% CI 1.3-6.3), while B. melitensis was detected more in sheep (OR = 3.6, 95% CI 2.0-6.7) and goats (OR = 1.7, 95% CI 1.0-3.1). Both B. abortus and B. melitensis DNA were detected in humans and in multiple livestock host species, suggesting cross-transmission of these species among the different hosts. The detection of these two zoonotic Brucella species in humans further underpins the importance of One Health prevention strategies that target multiple host species, especially in the multi-host livestock populations.

Prevalence of Brucella spp. in raw milk and artisanal cheese tested via real-time qPCR and culture assay

Brucellosis is one of the most prevalent zoonotic diseases with worldwide distribution. Although the incidence of brucellosis varies widely in different regions, it is a major concern for public health around the world. This study aimed to determine the prevalence and quantity of Brucella spp. in sheep and goat raw milk, as well as artisanal cheeses produced in the North-west of Iran. To evaluate the intrinsic parameters that may affect the survival of Brucella spp., some of the cheese properties (e.g., pH, salt, moisture, and storage time before selling) were also assessed. A total of 572 samples consisting in 214 sheep raw milk, 92 goat raw milk, and 266 local artisanal cheese samples were collected. The artisanal cheeses were manufactured from a mixture of raw sheep and goat milk. According to the results, using quantitative real-time PCR (qPCR), 17.29%, 15.22%, and 22.93% of the sheep raw milk, goat raw milk, and artisanal cheese samples were found positive for Brucella spp., respectively. In comparison with culture assay, qPCR was 3.5 to 5 times (p < 0.05) more sensitive in the detection of Brucella spp. The results also revealed that the mean values of Brucella spp. load in sheep and goat raw milk and artisanal cheeses were 1.22, 1.55, and 1.43 log cell/ml or g, respectively. A positive correlation was found between Brucella load and successful detection of Brucella spp. by culture assay. Data also suggested a correlation (p < 0.01) between the load of Brucella spp. estimated by qPCR and pH value, salt content, and storage period of the cheese samples. However, Brucella spp. load did not correlate significantly with the moisture content. Based on the results, in any of the cheese samples with a pH value less than 4.5 and a storage period more than five months, no contamination with Brucella spp. was detected.

Development of Human Vectored Brucellosis Vaccine Formulation: Assessment of Safety and Protectiveness of Influenza Viral Vectors Expressing Brucella Immunodominant Proteins in Mice and Guinea Pigs

In this paper, we first used recombinant influenza viral vector (rIVV) subtype H5N1 expressing from the open reading frame of NS1 80 and NS1 124 amino acids of Brucella outer membrane proteins (Omp) 16 and 19, ribosomal L7/L12, and Cu-Zn superoxide dismutase (SOD) proteins to develop a human brucellosis vaccine. We made 18 combinations of IVVs in mono-, bi-, and tetravalent vaccine formulations and tested them on mice to select the safest and most effective vaccine samples. Then, the most effective vaccine candidates were further tested on guinea pigs. Safety of the rIVV-based vaccine candidate was evaluated by a mouse weight-gain test. Mice and guinea pigs were challenged with the virulent strain B. melitensis 16M. The protective effect of the rIVV-based vaccine candidate was assessed by quantitation of Brucella colonization in tissues and organs of challenged animals. All vaccine formulations were safe in mice. Tested vaccine formulations, as well as the commercial B. melitensis Rev.1 vaccine, have been found to protect mice from B. melitensis 16M infection within the range of 1.6 to 2.97 log₁₀ units (P < 0.05). Tetravalent vaccine formulations from the position of NS1 80 amino acids (0.2 ± 0.4), as well as the commercial B. melitensis Rev.1 vaccine (1.2 ± 2.6), have been found to protect guinea pigs from B. melitensis 16M infection at a significant level (P < 0.05). Thus, tetravalent vaccine formulation Flu-NS1-80-Omp16+Flu-NS1-80-L7/L12+Flu-NS1-80-Omp19+Flu-NS1-80-SOD was chosen as a potential vaccine candidate for further development of an effective human vaccine against brucellosis. These results show a promising future for the development of a safe human vaccine against brucellosis based on rIVVs.