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Dagnaw et al. BMC Public Health (2024) 24:3495
https://doi.org/10.1186/s12889-024-21042-2 BMC Public Health
*Correspondence:
Haileyesus Dejene
haileyesus.dejene@uog.edu.et
Full list of author information is available at the end of the article
Abstract
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 predened 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 eects 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 nal analysis from a total of 1,427
identied 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 identied 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 eects were detected.
Conclusion The ndings indicate that brucellosis continues to pose a signicant 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.
Human and animal brucellosis and risk factors
for human infection in Ethiopia: a systematic
review and meta-analysis (2015–2024)
Gashaw GetanehDagnaw1, YordanosMamuye2 and HaileyesusDejene2*
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Dagnaw et al. BMC Public Health (2024) 24:3495
Introduction
Brucellosis is one of neglected zoonotic diseases caused
by bacteria of the genus Brucella. ese Gram-negative,
facultative, and intracellular coccobacilli aect both
humans and a variety of animals, including cattle, goats,
sheep, camels, pigs, and dogs. e Brucella species of
signicant zoonotic importance are Brucella melitensis,
Brucella abortus, Brucella suis, and Brucella canis [1,
2]. e bacterium spreads through direct contact within
same animal species and can inadvertently infect second-
ary hosts, such as humans. Humans primarily acquire
the infection through contact with infected animals and
the consumption of fresh, unprocessed animal products.
Other possible means of acquiring brucellosis include
person-to-person transmission (such as through blood
donation or tissue transplantation) and infection by a
contaminated environment [3, 4]. Brucellosis is also an
occupational hazard for livestock farmers, dairy workers,
veterinarians, slaughterhouse workers, and laboratory
personnel [5].
In most developed nations, incidence of brucello-
sis has been steadily declining and, in some cases, even
eradicated. However, this is not the case in low-income
and middle-income countries, where it continues to be
a public health and animal health concern [6]. Its main
consequences include reproductive losses in livestock
and debilitating illness in humans [7]. Additionally, issues
related to its therapeutic management, demographic
changes, signicant increases in complications, persis-
tence in pastoral communities, and a rising prevalence in
regions where small ruminants are common have been
documented [8–11]. Brucellosis also has major economic
signicance due to the lost productivity of patients from
daily activities and reduced animal production [12, 13].
In Ethiopia, animals and humans share the same envi-
ronment, particularly in rural and semi-urban areas,
where over 80% of the population relies on livestock for
their livelihoods. is close and frequent interaction with
animals leads to a higher prevalence of brucellosis in both
humans and animals [6, 14]. Transmission of brucellosis
to humans occurs through the consumption of unpas-
teurized dairy products or direct contact with infected
animals, placentas, or aborted fetuses [5, 15].
Previous studies have demonstrated that brucellosis
remains an important disease in Ethiopia. A systematic
review and meta-analysis conducted in 2016 reported
a high prevalence in both animals and humans [6].
Although several studies have assessed seroprevalence
and its signicance in Ethiopia over the past decade,
comprehensive country-level estimates for both animals
and humans, as well as the associated risk factors, remain
limited. erefore, we conducted this systematic review
and meta-analysis to estimate the occurrence of brucel-
losis in animals (mainly cattle, dogs, camels, sheep, and
goats) and humans and to identify the associated risk fac-
tors in Ethiopia in recent years. is study is crucial as it
quanties the burden of brucellosis and identies key risk
factors. ese insights are important for informing pub-
lic health strategies and policies aimed at controlling and
preventing brucellosis, ultimately leading to improved
health outcomes and economic benets by reducing the
disease’s impact on human health and animal production.
Methodology
Study protocols
is systematic review and meta-analysis were conducted
from May 2024 to July 2024. is study was conducted
according to the Preferred Reporting Items for System-
atic Reviews and Meta-Analyses (PRISMA) guidelines by
Page et al. [16], and the checklist was used to ensure the
inclusion of relevant information (Supplementary File 1).
Seroprevalence estimates of brucellosis in both animals
(referring to cattle, sheep, goats, camels, and dogs) and
humans, as well as risk factors associated with human
brucellosis in Ethiopia, were the outcomes of interest.
Description of study setting
e meta-analysis was carried out in Ethiopia, a country
located in the Horn of Africa, located between the lati-
tudes of 3° 00′ N and 15° 00′ N and the longitudes of 32°
30′ E and 48° 00′ E. Ethiopia covers a total land area of
1.04million square kilometers and has a population of
123.4million people, making it the second most popu-
lous country in Africa, after Nigeria. e country is well-
suited for agricultural production, with an estimated
livestock population of approximately 70million cattle,
52.5 million sheep, 42.9 million goats, 8 million cam-
els, and 56million chickens. Ethiopia features a diverse
topography, which gives rise to various agro-climatic
zones [17].
Literature search strategy
Academic databases or research databases such as
PubMed, ScienceDirect, Scopus, PubMed Central, Web
of Science, and Google Scholar were used to research
articles focusing on brucellosis in humans and animals
(mainly cattle, dogs, camels, sheep and goats) in Ethio-
pia. e languages of publication and the years were
restricted to English and from 2015 to July 2024, respec-
tively. e article search was conducted using various
MeSH (medical subject heading) terms, including: (a)
‘seroprevalence OR prevalence’ or sero-epidemiology’
Keywords Brucella, Camel, Cattle, Dog, Human, Shoat, Sero-prevalence, Neglected zoonotic disease
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Dagnaw et al. BMC Public Health (2024) 24:3495
AND ‘Brucellosis’ OR ‘Brucella melitensis’ OR ‘Brucella
abortus’ OR ‘Brucella suis’ OR ‘Brucella canis’ AND
‘cattle’ OR ‘bovine’ OR ‘sheep’ OR ‘goat’ OR ‘ovine’ OR
‘shoats’ OR ‘camel’ OR ‘dog’ AND ‘Ethiopia’; (b) ‘serop-
revalence OR prevalence’ or sero-epidemiology’ AND
‘Brucellosis’ OR Malta fever OR Brucella OR ‘Brucella
melitensis’ OR ‘Brucella abortus’ OR ‘Brucella suis’ OR
‘Brucella canis’ AND ‘Human’ and ‘Ethiopia’. Dierent
regions of Ethiopia, such as Amhara, Oromia, Tigray,
etc., as well as keywords like “incidence” and “risk fac-
tors,” were used in the search engine to ensure that no
relevant article was excluded. Mendeley version 1.19.8
(Meneley Ltd) software was used for removal of duplica-
tion of articles.
Inclusion and exclusion criteria
e inclusion and exclusion criteria were dened based
on the relevance of the articles to the research questions
of interest. Papers were included if they met the following
eligibility criteria: original peer-reviewed research arti-
cles conducted in Ethiopia; cross-sectional, case-control,
or cohort studies; full-text articles; abstracts if they pre-
sented the required information; studies targeting popu-
lations within any management system; studies using the
Rose Bengal Plate Test (RBPT), Enzyme-Linked Immu-
nosorbent Assay (ELISA), or Complement Fixation Test
(CFT); studies providing the total sample size and out-
come of interest; and studies published in English from
2015 to July 2024. Articles were excluded if they were sys-
tematic reviews and meta-analyses, case reports, studies
conducted before 2016, or those that were unavailable.
Additionally, articles were excluded if they had duplica-
tion (repeated articles or data), inconsistent data (inco-
herent data within tables or narrative sections that could
not be resolved), or were inaccessible [18].
Data extraction
Records obtained from various electronic databases,
indexing services, and directories were imported into
Mendeley reference manager software version 1.19.8
(Meneley Ltd) in compatible formats. Duplicate records
were identied, documented, and removed using Men-
deley. Some duplicates were addressed manually because
of variations in reference styles across dierent sources.
Two researchers GGD and HD independent screened
the articles based on the predened inclusion criteria.
Discrepancies between the two authors were resolved
independently by a third researcher, YM. HD and YD
independently extracted the data, while GGD inde-
pendently assessed it. e extracted data from eligible
articles included the rst author, year of publication,
year of study, location (region), species (camel, cattle,
sheep, goat, and humans), serological test methods, the
laboratory where the serological tests were conducted,
and the number of samples examined and positive.
Quality assessment
We employed strategies to minimize bias and random
error, including a thorough search for all potentially rel-
evant articles and the use of clear, reproducible criteria
for selecting articles for the review. Research designs and
study characteristics were evaluated, data were synthe-
sized, and results were interpreted following a predened
systematic approach that adheres to evidence-based
methodological principles. HD and GGD reviewed titles,
abstracts, and full-text articles to determine which stud-
ies to include and exclude in the review. YM resolved dis-
agreements between the two reviewers. GGD, HD, and
YM assessed the ability of the articles to full the pre-
dened eligibility criteria. GGD and HD appraised each
included study for study quality assessment using the
appraisal tool for cross-sectional studies (Supplementary
File 2). is checklist contains 20 components that con-
stitute the title, abstract, introduction, methods, results,
and discussion portions of the article. e objectives, var-
ious components of the methodology (e.g., study design,
sample size, study population, bias, statistical methods),
ndings, limitations, and funding of the investigations
are all covered by the checklist [19]. e supplement two
checklists were assessed according to the previous quality
studies described by [20, 21].
Data synthesis and statistical analysis
e extracted data was entered into an Excel spread-
sheet and imported to R software version 4.4.1 for analy-
sis. e random-eect model was employed to calculate
the pooled seroprevalence with a 95% condence inter-
val (CI). Heterogeneity and heterogeneity quantica-
tion were determined by using Cochran’s Q-test and I2
index, respectively. Based on the Higgins classication
approach, I2 values of more than 0.7 were regarded as
high heterogeneity [22]. Subgroup analyses for the pri-
mary outcome (seroprevalence of brucellosis) was done
using DerSimonian and Laird model by considering geo-
graphical locations (northern, southern, central, western
and eastern Ethiopia), publication year and laboratory
technique employed (RBPT, CFT or cELISA) [23, 24].
Small study eects and publication bias presence was
then visualized using funnel plot diagrams and, Egger’s
asymmetry tests, respectively [25]. Meta-regression anal-
ysis was conducted to identify potential sources of varia-
tion in the pooled seroprevalence. Standard error with
95% condent interval (CI) were calculated. A p-value
less than 0.05 (P < 0.05) was considered signicant in all
analyses [19].
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Dagnaw et al. BMC Public Health (2024) 24:3495
Results
Search result
is systematic review and meta-analysis focused on
published studies about brucellosis in both animals and
humans in Ethiopia. e literature search was conducted
from May to July 2024, with a language restriction to
English, targeting studies involving animals and humans
published between 2015 and 2024. A total of 1,427 arti-
cles were identied, of which 810 were rejected based on
their titles and abstracts for irrelevance to our review.
e remaining 617 studies underwent further evaluation,
resulting in the exclusion of 320 duplicates or inappropri-
ate articles. A total of 297 full-text papers were accessed
and assessed for eligibility using pre-set criteria; 258
articles were excluded based on study area and other fac-
tors. irty-nine articles were included in this systematic
review and meta-analysis (Fig.1).
Study characteristics
e characteristics of the 39 studies included in this sys-
tematic review and meta-analysis are shown in Table1.
All the studies were cross-sectional in design and were
conducted in Central, Northern, Eastern, Western, and
Southern Ethiopia, with sample sizes ranging from 80 to
2,982. From the 39 included studies, 64 seroprevalence
reports of brucellosis were extracted and used in the
Fig. 1 PRISMA owchart for the selection of studies on the sero-prevalence of brucellosis in Ethiopia from 2015 to 2024
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Dagnaw et al. BMC Public Health (2024) 24:3495
No Author Regional Location Diagnostic test Study population Sample size Event ST Event CT
1 [26] Eastern Ethiopia RBPT & CFT Human 211 5 1
2 [26] Eastern Ethiopia RBPT & CFT Cattle 268 7 0
3 [26] Eastern Ethiopia RBPT & CFT Sheep 108 1 0
4 [26] Eastern Ethiopia RBPT & CFT Goat 172 5 3
5 [26] Eastern Ethiopia RBPT & CFT Camel 183 9 0
6 [27] Western Ethiopia RBPT & CFT Cattle 423 19 17
7 [28] Southern Ethiopia cELISA Goat 789 -- 137
8 [29] Central Ethiopia RBPT & CFT Human 149 7 2
9 [30] Northern Ethiopia RBPT & ELISA Human 444 140 70
10 [31] Southern Ethiopia RBPT & CFT Goat 293 0 0
11 [31] Southern Ethiopia RBPT & CFT Sheep 213 0 0
12 [32] Southern Ethiopia cELISA Cattle 788 -- 60
13 [33] Central Ethiopia cELISA Sheep 1091 -- 97
14 [33] Central Ethiopia cELISA Cattle 2982 -- 47
15 [33] Central Ethiopia cELISA Camel 201 -- 25
16 [34] Western Ethiopia cELISA Cattle 424 -- 14
17 [35] Southern Ethiopia cELISA Cattle 750 -- 18
18 [35] Southern Ethiopia cELISA Sheep 196 -- 3
19 [35] Southern Ethiopia cELISA Goat 621 -- 25
20 [35] Southern Ethiopia cELISA Human 341 -- 9
21 [36] Eastern Ethiopia RBPT & CFT Sheep 111 1 1
22 [36] Eastern Ethiopia RBPT & CFT Goat 213 5 3
23 [37] Northern Ethiopia RBPT & CFT Sheep 2409 120 118
24 [38] Southern Ethiopia RBPT & CFT Sheep 179 1 1
25 [38] Southern Ethiopia RBPT & CFT Goat 609 39 31
26 [39] Eastern Ethiopia cELISA Camel 450 -- 13
27 [39] Eastern Ethiopia cELISA Human 250 -- 5
28 [39] Southern Ethiopia RBPT & CFT Cattle 461 33 31
29 [41] Southern Ethiopia RBPT & CFT Cattle 614 21 17
30 [42] Eastern Ethiopia cELISA Human 178 -- 5
31 [42] Eastern Ethiopia cELISA Cattle 135 -- 2
32 [42] Eastern Ethiopia cELISA Camel 171 -- 1
33 [42] Eastern Ethiopia cELISA Goat 297 -- 0
34 [42] Eastern Ethiopia cELISA Sheep 269 -- 0
35 [43] Northern Ethiopia cELISA Human 809 -- 333
36 [43] Northern Ethiopia cELISA Cattle 604 -- 43
37 [43] Northern Ethiopia cELISA Camel 734 -- 58
38 [43] Northern Ethiopia cELISA Goat 2466 -- 251
39 [43] Northern Ethiopia cELISA Sheep 856 -- 71
40 [44] Central Ethiopia RBPT & CFT Cattle 503 2 2
41 [45] Central Ethiopia RBPT & CFT Human 166 7 2
42 [46] Eastern Ethiopia RBPT & CFT Cattle 384 5 1
43 [47] Southern Ethiopia cELISA Cattle 268 -- 26
44 [47] Southern Ethiopia cELISA Goat 246 -- 11
45 [48] Northern Ethiopia RBPT & CFT Sheep 552 25 1
46 [48] Northern Ethiopia RBPT & CFT Goat 1345 114 11
47 [48] Northern Ethiopia RBPT & CFT Cattle 420 50 36
48 [49] Central Ethiopia RBPT & ELISA Cattle 1550 43 1
49 [50] Central Ethiopia RBPT & ELISA Cattle 804 19 19
50 [51] Northern Ethiopia RBPT & CFT Goat 226 27 17
51 [52] Central Ethiopia cELISA Dog 385 -- 16
52 [53] Southern Ethiopia RBPT & CFT Sheep 1536 105 83
53 [54] Western Ethiopia cELISA Cattle 1152 -- 21
Table 1 Descriptive summary of the included studies on the sero-prevalence of brucellosis in Ethiopia
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Dagnaw et al. BMC Public Health (2024) 24:3495
analysis. Of which, 36 reports provided results based on
both screening and conrmatory tests (Table1).
Meta-analysis and bias assessment
For the current meta-analysis, 57 ndings reported via
conrmatory tests were used. e overall pooled serop-
revalence of brucellosis was 5.0% (95% CI: 3.0, 6.0). ere
was signicant heterogeneity in the reported seropreva-
lence of brucellosis between studies (tau² = 0.0038, H²
= 255.9, I² = 99.61%, Q-test = 1954.99, df = 56, p ≤ 0.001).
Despite the considerable heterogeneity between studies,
the studies were roughly weighted equally, with individ-
ual study weights ranging from 1.1 to 1.8% (Fig.2).
Moreover, the pooled sero-prevalence of brucello-
sis based on screening tests was 5.0% (95% CI: 3.0, 7.0).
ere was signicant heterogeneity in the reports of bru-
cellosis sero-prevalence between studies (tau2 = 0.0027,
H2 = 63.23, I²=95.0%, Q-test = 657.91, df = 33, p < 0.0001).
However, studies were roughly weighted equal, with indi-
vidual study weights ranging from 2.6 to 3.1% (Fig.3).
Quality assessment result
In this review, a spectrum of studies was evaluated
for their quality, which ranged from low to moderate.
It is worth noting that all studies, without exception,
employed a clear sample size estimation method. In the
current meta-analysis, all articles utilized the random
sampling method procedure as outlined by [64]. More-
over, all 39 studies (100%) successfully obtained a sample
frame from a suitable population that closely resembled
the target or reference population being investigated.
Out of the total number of studies, 34 (87.2%) fullled
the requirements for six out of the 20 questions, namely:
aims/objectives, denition of target/reference popula-
tion, internal consistency of results, authors’ justication
of the results, sample size justication, and analysis of
appropriate techniques in the methods section. Conicts
of interest and descriptions of statistical methods used
were also addressed.
Subgroup meta-analysis
Subgroup analysis, based on geographical location,
results are presented in Table2. e highest sero-prev-
alence of brucellosis was recorded in Northern Ethiopia
at 8.3% (95% CI: 6.7, 9.8), while the lowest was recorded
in Eastern Ethiopia at 1.4% (95% CI: 0.0, 2.9). Addition-
ally, the heterogeneity results from the subgroup analysis
indicated a high level of heterogeneity between the dier-
ent groups (tau2 = 0.0007, I² = 97.1%, Q-test = 44.38, df = 4,
p ≤ 0.001) (Supplementary Fig.1).
e results presented in Table 3 show the subgroup
analysis, which was performed based on the study pop-
ulation. e 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). e seroprevalence of brucel-
losis in humans in the current study is lower than that
reported in studies conducted before 2016, which found
a seroprevalence of 8% (95% CI: 3.0, 19.0) (Supplemen-
tary Fig.2).
e result presented in Table4 showed the sub-group
analysis which was performed by laboratory tests.
Accordingly, the seroprevalence of brucellosis was higher
in studies test by cELISA (6.4% (95% CI: 5.3, 7.5)) when
compared with studies tested by other laboratory tests
(Supplementary Fig.3).
e result presented in Table5 showed the sub-group
analysis which was performed by categorizing the study
years. Accordingly, the seroprevalence of brucellosis
was higher in studies conducted between 2019 and 2021
(5.5% (95% CI: 4.3%, 6.7%)) when compared with studies
conducted between 2022 and 2024 (3.9% (95% CI: 2.8%,
5.1%) and studies conducted between 2015 and 2018
(2.8% (95% CI: 0.8%, 4.8%) (Supplementary Fig.4).
Publication bias
Publication bias and small study eects were assessed
using funnel plot observation and Egger’s test (Fig. 4).
e egger test result is signicant, so there is evidence
for asymmetry. e results, comparing eect estimates
No Author Regional Location Diagnostic test Study population Sample size Event ST Event CT
54 [55] Eastern Ethiopia RBPT & CFT Goat 2070 15 5
55 [56] Northern Ethiopia RBPT & CFT Cattle 420 50 24
56 [57] Northern Ethiopia RBPT & CFT Camel 250 19 8
57 [57] Northern Ethiopia RBPT & CFT Human 120 12 4
58 [58] Eastern Ethiopia RBPT & CFT Camel 350 29 7
59 [59] Southern Ethiopia RBPT & CFT Sheep 546 26 22
60 [59] Southern Ethiopia RBPT & CFT Goat 144 2 1
61 [60] Eastern Ethiopia CFT Cattle 967 -- 13
62 [61] Central Ethiopia RBPT & CFT Cattle 352 4 2
63 [62] Western Ethiopia CFT Cattle 80 -- 18
64 [63] Southern Ethiopia RBPT & CFT Cattle 384 8 6
RBPT: Rose Benga l plate test; CFT: Complement xation test; c-ELISA: compe titive Enzyme- linked immunosorbent a ssay; CT: Conrmatory test ; ST: Screenin g test
Table 1 (continued)
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Dagnaw et al. BMC Public Health (2024) 24:3495
against their standard errors, indicated no signicant
publication bias, with a p-value of 0.075 (Table6).
Meta regression
In the current meta-analysis, univariable meta-regression
was used to identify potential sources of variation in the
pooled seroprevalence, considering study location, study
population, laboratory test, and study year as poten-
tial factors. Each variable was analyzed separately in
the meta-regression analysis, with study year treated as
a categorical variable. In the multivariable meta-regres-
sion analysis, variables with p-values less than 0.47
were included. e nal multivariable analysis retained
Fig. 2 Forest plot showing the pooled sero-prevalence of Brucellosis by conrmatory test in Ethiopia
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Page 8 of 14
Dagnaw et al. BMC Public Health (2024) 24:3495
laboratory test and study location as factor variables due
to their considerable impact (Table7).
Potential risk factor identied for Brucella infection in Human
e epidemiology of brucellosis is inuenced by vari-
ous environmental factors (such as food habits, sanitary
conditions, and contact with aborted fetuses) and socio-
demographic factors (including age, sex, occupation,
education, marital status, service year, and residence).
ese factors collectively impact the distribution of the
disease globally and within individual countries. In this
study, sixteen risk factors were identied. e factors that
Table 2 Subgroup analysis for comparing the sero-prevalence of
brucellosis in dierent study areas
Study location K Prevalence
(95% CI)
I2tau2p-
value
Eastern Ethiopia 13 1.4 (0.0, 2.9) 66.0% 0.0007 0.001
Western Ethiopia 4 4.6 (1.6, 7.6) 88.0% 0.0007 0.001
Southern Ethiopia 16 4.6 (3.2, 5.9) 93.0% 0.0007 0.001
Central Ethiopia 10 2.9 (1.1, 4.6) 96.0% 0.0007 0.001
Northern Ethiopia 14 8.3 (6.7, 9.8) 99.0% 0.0007 0.001
Overall 57 5.0 (3.0, 6.0) 99.61% 0.0038 0.001
K = Number of studie s, CI = Condence interval
Fig. 3 Forest plot showing the pooled sero-prevalence of Brucellosis by screening test in Ethiopia
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Dagnaw et al. BMC Public Health (2024) 24:3495
showed a signicant association (p < 0.05) with the occur-
rence of brucellosis include age, sex, consumption of
raw milk and meat, marital status, residence, education
level, drinking milk from aborted animals, contact with
aborted materials or fetuses, occupation, presence of
seropositive animals in the household, assisting dur-
ing birthing or calving, disposing of or contacting dead
fetuses or retained fetal membranes (RFM), and human
housing with animals (Table8).
Table 3 Subgroup analysis for comparing the sero-prevalence of brucellosis between study population
Study population K Prevalence (95% CI) I2tau2p-value
Human 9 6.9 (4.9, 8.8) 99.0% 0.0007 0.001
Goat 11 4.6 (2.9, 6.3) 98.0% 0.0007 0.001
Cattle 21 3.5 (2.2, 4.7) 95.0% 0.0007 0.001
Sheep 9 3.8 (1.9, 5.6) 97.0% 0.0007 0.001
Camel 6 4.3 (1.9, 6.6) 92.0% 0.0007 0.001
Dog 1 4.2 (0.0, 9.8) ** 0.0007 **
Overall 57 5.0 (3.0, 6.0) 99.61% 0.0038 0.001
K = Number of studie s, CI = Condence interval, **= Value f or which comparison do es not compute due to zero degr ee of freedom
Table 4 Subgroup analysis for comparing the sero-prevalence of
brucellosis between laboratory tests
Laboratory test K Prevalence (95% CI) I2tau2p-value
RBPT & CFT 28 2.6 (1.6, 3.6) 92.0% 0.0007 0.001
cELISA 24 6.4 (5.3, 7.5) 98.0% 0.0007 0.001
RBPT & cELISA 3 4.9 (1.9, 8.1) 98.0% 0.0007 0.001
CFT 2 5.4 (0.8, 9.9) 95.0% 0.0007 0.001
Overall 57 5.0 (3.0, 6.0) 99.61% 0.0038 0.001
K = Number of studie s, CI = Condence interval
Table 5 Subgroup analysis for comparing the sero-prevalence of
brucellosis by study year
Study year K Preva-
lence
(95% CI)
I2tau2p-
val-
ue
Studies conducted be-
tween 2015–2018 (A)
8 2.8 (0.8,
4.8)
99.0% 0.0008 0.001
Studies conducted be-
tween 2019–2021 (B)
24 5.5 (4.3,
6.7)
98.0% 0.0008 0.001
Studies conducted be-
tween 2022–2024 (C)
25 3.9 (2.8,
5.1)
95.0% 0.0008 0.001
Overall 57 5.0 (3.0,
6.0)
99.61% 0.0038 0.001
Table 6 Eggers test for publication bias assessment
Standard eect Coecient z-value p-value 95% CI
Slope -2.1 -7.6 0.0001 -2.5 - -1.7
Bias -0.16 1.20 0.075 -0.29 – -0.067
Table 7 Final multivariable Meta -regression model
Variables Coecient P-value 95% CI
Study location
Central Ethiopia Ref.
Eastern Ethiopia -0.02 0.154 -0.05, 0.01
Northern Ethiopia 0.06 0.000 0.035, 0.089
Southern Ethiopia 0.017 0.227 -0.01, 0.045
Western Ethiopia 0.019 0.335 -0.02, 0.061
Laboratory test
CFT Ref.
RBPT & CFT -0.11 0.000 -0.16, -0.06
RBPT & cELISA -0.08 0.016 -0.14, -0.015
cELISA -0.06 0.011 -0.12, -0.015
Fig. 4 Funnel plot showing small study eects by conrmatory test
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Page 10 of 14
Dagnaw et al. BMC Public Health (2024) 24:3495
Discussion
Pooled sero-prevalence estimate of brucellosis
Ethiopian communities are characterized by limited
resources, poor living conditions, and feeding habits,
along with close contact with various domestic animals
(such as cats, goats, sheep, cattle, camels, and equines).
Low awareness and inadequate hygiene further contrib-
ute to the risk of infection [65]. Additionally, the con-
sumption of raw or undercooked meat and poor hygiene
practices increase the risk of brucellosis infection [66].
In the current systematic review and meta-analysis,
which included 39 original studies, the pooled serop-
revalence of brucellosis in Ethiopia was found to be 5.0%
(95% CI: 3.0, 6.0). is nding is higher compared to the
pooled seroprevalence reported by Adabi et al. [67] in
Iran (3%), Asmare et al. [65] in Ethiopia (3.3%), Ran et al.
[68] in China (2.3%), and Tesfaye et al. [66] in Ethiopia
(3%). However, it is lower than the 8% (95% CI: 7.0, 9.0)
reported by Suresh et al. [69] from a systematic review
and meta-analysis in livestock across Africa and Asia.
Additionally, the current nding is lower than the serop-
revalence reported by Dadar et al. [70] (9.23%), Moham-
med et al. [71] in Sudan (17%), Akinyemi et al. [72] in
Nigeria (13.3%), Li et al. [73] in Africa and Asia (8.5%),
and Shi et al. [74] in Africa (9.7%) from global meta-
epidemiological data and systematic reviews. Variations
in seroprevalence among studies may be attributed to
dierences in environmental conditions, study popula-
tions, farming systems, and sample sizes. Although many
reports have limited geographic coverage or focus on
specic agro-ecologies, these ndings suggest that bru-
cellosis could be a widespread issue in Ethiopia [60].
In the current meta-analysis, the highest pooled sero-
prevalence of brucellosis was recorded in Northern
Ethiopia (8.3%), while the lowest was found in Eastern
Ethiopia (1.4%). is contrasts with pooled seropreva-
lence reported in Western Ethiopia (4.6%), Southern
Ethiopia (4.6%), and Central Ethiopia (2.9%). ese
variations in seroprevalence across dierent locations
may be attributed to dierences in the number of stud-
ies included in the meta-analysis. e current nding is
higher than those reported in various individual studies
across the country [29, 44–46, 49, 50, 54, 55, 58, 60, 61,
63]. Discrepancies in disease prevalence across dierent
studies may be due to variations in sample size and geo-
graphical location.
Among the study populations included in the current
meta-analysis, the highest pooled seroprevalence of bru-
cellosis was observed in humans (6.9%), followed by goats
(4.6%), camels (4.3%), dogs (4.2%), sheep (3.8%), and cat-
tle (3.5%). e observed high pooled seroprevalence of
brucellosis in human might be due to feeding habits and
close contact with infected animals and their discharges
[35, 43]. Moreover, the current overall seroprevalence in
humans is lower than the pooled seroprevalence reported
by Mia et al. [75] in Asia and Africa (14%), Khoshnood et
al. [76] in Iran (15.27%), and Akinyemi et al. [72] in Nige-
ria (17.6%), based on global meta-epidemiological data.
Conversely, the current nding is higher than the pooled
seroprevalence reported by Njeru et al. [77] in Kenya
(3%) and Tadesse [6] in Ethiopia (6.7%). Furthermore, the
current pooled seroprevalence for goats is higher than
the rates reported by Sibhat et al. [14] in Ethiopia (4%)
and Ran et al. [68] in China (2.3%). However, it is lower
than the pooled seroprevalence reported by Tadesse [6]
in Ethiopia (5.3%) and Adabi et al. [67] in Iran (5%). e
current pooled seroprevalence for camels, sheep, and
cattle is higher than the rates reported by Sibhat et al.
Table 8 Potential Risk factor identied for human brucellosis
Variable Risks (p < 0.05) Not associated (p > 0.05)
Age Adult (≥ 50) [26, 35, 43] [29, 39, 42, 45, 57]
Sex Female [26, 39]; Male [30, 35] [29, 42, 43, 45, 57]
Consumption of raw meat and milk Raw milk consumption [26, 30, 39, 45] [35]
Marital status Married [35] [29, 57]
Residence or Origin Rural [30]; Afar pastoralist [43] [29]
Service year [29]
Education level Illiterate [30] [29, 45, 57]
Drinking of raw milk from aborted animal [30, 45]
Touching of aborted materials or fetus [30]
Occupation Pastoralist [30, 57]
Animal ownership [60]
Presence of seropositive animal at household [35] [39]
Assisting during birthing or calving [35] [39]
Disposing or contact with dead fetus or RFM [39, 45] [35]
Human housing with animal Common housing [45]
Family size [57]
RFM: Retained fetal membranes
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Page 11 of 14
Dagnaw et al. BMC Public Health (2024) 24:3495
[14] in Ethiopia, Tadesse [6] in Ethiopia, Adabi et al. [67]
in Iran, and Tesfaye et al. [66] in Ethiopia. ese regional
variation in seroprevalence may be attributed to dier-
ences in the number of studies included, geographical
locations, climatic factors, and management practices.
Furthermore, signicant progress in the prevention and
control of brucellosis has been achieved through compre-
hensive measures that focus on understanding the infec-
tion sources, transmission modes, and susceptible hosts
[76, 78].
Potential risk factors identied for human infection
e current ndings indicate that age, sex, marital sta-
tus, residence, and education level are signicant socio-
demographic factors associated with Brucella infection.
Specically, as the ages of study subjects increases, their
risk of disease also increases. Similarly, pastoralist life-
style, rural residence, and illiteracy are identied as risk
factors for brucellosis in humans. ese ndings are
consistent with previous research [76, 77, 79–82]. e
age-related increase in seroprevalence aligns with the
endemic pattern of infection in humans. Additionally,
males are at higher risk of contracting brucellosis due to
their involvement in livestock handling and the consump-
tion of uncooked animal products, particularly in pasto-
ral areas. Igawe et al. [82] reported that animal slaughter
in northern Nigeria is predominantly a male activity,
further supporting the higher infection risk among men
compared to women. Moreover, men often carry out
obstetric tasks in livestock, while female household heads
are more likely to practice safer measures, possibly due to
greater exposure to health workers during antenatal care
or child welfare visits [83]. is discrepancy may contrib-
ute to the higher rate of brucellosis transmission among
men compared to women.
e present ndings reveal a strong association
between human brucellosis and factors such as handling
aborted material, drinking raw milk, consuming raw
milk from aborted animals, and drinking raw milk from
cows with retained fetal membrane (RFM). is is con-
sistent with studies by Narimisa et al. [80], Abedi et al.
[84], Njeru et al. [77], John et al. [85], and Schelling et
al. [86], which also identied these factors as signicant
risk contributors for brucellosis in humans. Furthermore,
our ndings indicate that Brucella seroprevalence varies
among dierent working groups, with some groups hav-
ing higher contact with risk factors than others. Workers
involved in animal parturition were found to be twice as
likely to test positive for brucellosis compared to other
groups. In Africa, farmers and butchers often assist
in parturition, handle retained placentas, and trade in
gravid uteruses [4]. Studies by Aworh et al. [87], Esmaeili
et al. [88] in Iran, and Swai and Schoonman [89], in Tan-
zania showed that workers using protective hand and
foot gear were at least 50% less likely to test positive for
Brucella. Additionally, Awah-Ndukum et al. [90] in Cam-
eroon found that all Brucella IgG-seropositive respon-
dents did not use personal protective equipment, such as
gloves, during their work.
Conclusion
e results of this systematic review and meta-analysis
indicate that brucellosis continues to be a signicant
disease aecting both humans and animals in Ethiopia.
e dierences in seroprevalence observed across stud-
ies could be attributed to variations in laboratory testing
methods and geographical locations. Key risk factors for
human brucellosis identied include the consumption of
raw milk from animals that have aborted, direct contact
with aborted materials or fetuses, and occupational expo-
sure. ese ndings highlight the need for targeted pub-
lic health interventions and heightened awareness eort
to help reduce brucellosis incidence, especially among
high-risk populations.
Limitations of the study
Although the current study is the rst to summarize the
seroprevalence of brucellosis in Ethiopia over a 10-year
period, we acknowledge its limitations.
Abbreviations
c-ELISA Competitive Enzyme-linked immunosorbent assay
CFT Complement xation test
RBPT Rose Bengal plate test
RFM Retained fetal membranes
Supplementary Information
The online version contains supplementary material available at h t t p s : / / d o i . o r
g / 1 0 . 1 1 8 6 / s 1 2 8 8 9 - 0 2 4 - 2 1 0 4 2 - 2 .
Supplementary Material 1
Supplementary Material 2
Supplementary Material 3
Supplementary Material 4
Supplementary Material 5
Supplementary Material 6
Acknowledgements
We thank the authors of the literature.
Author contributions
Conceptualization and Methodology: GGD, YM, and HD; Data curation and
Formal analysis: GGD and HD; Software, Supervision and Validation: GGD
and HD; Writing- Original draft preparation: GGD, YM, and HD; Investigation,
Visualization, and Writing- Review and Editing: GGD and HD. All authors read
and approved the nal manuscript.
Funding
No funding was received for this research.
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
Page 12 of 14
Dagnaw et al. BMC Public Health (2024) 24:3495
Data availability
The data that support the ndings of this study are available from the
corresponding author upon reasonable request.
Declarations
Ethical approval
Ethical approval is not applicable. No animal or human experimentation was
undertaken.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Author details
1Department of Biomedical Sciences, College of Veterinary Medicine and
Animal Science, University of Gondar, P.O. Box 196, Gondar, Ethiopia
2Department of Veterinary Epidemiology and Public Health, College of
Veterinary Medicine and Animal Science, University of Gondar, P.O. Box
196, Gondar, Ethiopia
Received: 9 August 2024 / Accepted: 10 December 2024
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