Review on camel Brucellosis and it's zoonotic importance in Ethiopia.docx

Camel brucellosis and it's zoonotic importance in Ethiopia

1. BULE HORA UNIVERSITY






COLLEGE OF AGRICULTURAL SCIENCE AND VETERINARY MEDICINE


REVIEW ON CAMEL BRUCELLOSIS AND IT'S ZOONOTIC IMPORTANCE IN ETHIOPIA




Mohammed Abdela

2. School of Veterinary Medicine


Review on Camel Brucellosis and its zoonotic importance in Ethiopia

A paper Presented to the College of Agriculture and Veterinary Medicine for the partial fulfillment of the Course ……….




Mohammed Abdela

3. Advisor: Dr.Fuad Mohammed (DVM,MVSc, Assist. Prof)





April ,2025
Bule hora , Ethiopia


Table of Contents page
ACKNOWLEDGEMENTS . ......... 1
LISTS OF ABBREVIATIONS. 3
1.INTRODUCTION. 1
2. LITERATURE REVIEW. 5
2.1.2. Physical and biochemical characteristics of camel brucellosis5

4. 2.2. Epidemiology7
2.2.1. GLOBAL DISTRIBUTION OF CAMEL BRUCELLOSIS 9
2.2.2. Distribution of camel brucellosis in Africa9
2.2.3. DISTRIBUTION OF CAMEL BRUCELLOSIS in Ethiopia10
2.2.2. Source of infection and method of transmission11
2.2.3. Risk Factor12
2.2.4 Immune response13
2.3. Pathogenesis14
2.4. Clinical Manifestations16
2.5. Diagnostic Methods16
2.5.1. Bacteriological method17
2.5.2. Serological Methods17
2.5.3. Molecular method19
2.6. Treatment20
2.7. Zoonotic importance20
Brucellosis is an important zoonotic disease of public health implications accounting for more than 500,000 human cases per
annum worldwide (Seleemet al.,2010). The burden of the disease is enormous but yet remains under-prioritized globally
especially amongst the pastoralists and small-scale livestock farmers. Brucellosis is primarily a disease of animals and is
transmitted directly and indirectly to human cases (Hadush and Pal, 2013).20
2.8. Socio Economic Importance22
2.10. Prevention and Control of the Disease23
3 .CONCLUSION AND RECOMMENDATIONS 26
4. REFERENCE27

5. ACKNOWLEDGEMENTS
First of all, I would like to express my deepest thanks to Allah, who gave me the health, strength and patience to finish this work. Next I would
like to say thanks to my advisor, Dr. Fuad Mohammed (DVM MVSC, Assist, Prof.) for his excellent guidance and advice, valuable stimulating
suggestions, needed encouragement and supervision, and above all his help to me until the seminar paper presentation. I would also like to
acknowledge with much appreciation to my family, for their endless help, love and moral support in every situation facing me.
Special thanks go to all of my friends, who help me in materials needed and they value me the important things in the duration that might be
forwarded. I am extremely delighted in extending my thanks to Bule Hora University for facilitating internet access

6. LISTS OF ABBREVIATIONS

C-ELISA Competitive Enzyme Linked Immunosorbent Assay
CSF Cerebrospinal Fluid
FAO Food and Agricultural Organization
IG Immunoglobulin
LPS Lipopolysaccharide
OIE Office International Des Epizootics
OWCS Old World Camels
PCR Polymerase Chain Reaction
RBPT Rose Bengal Plate Test
SAT Serum Agglutination Test
SPP Species
CFT. Complement fixation test
iELISA. Indirect ELISA

7. LIST OF TABLES
Table 1: Summary of Brucella strains, hosts and its mode of transmission.
Table 2: :Seroprevalence of camel brucellosis in some north and sub Saharan African countries

8. Summary
Camels are versatile, vital domestic animals that are best adapted to harsh environmental conditions prevailing in extreme semi-arid and arid
areas. They ensure food security in pastoral communities by producing milk and meat. They are also sources of hides, which are used as bed
sheets; serve as means of transportation and draught power. Long lactation and ability to maintain milk production over long dry spells are
important facets of camel production. Brucellosis is an infectious disease of domestic and wild animals with serious zoonotic and economic
implications in humans. The disease is an important public health problem in many parts of the world .Which is mainly manifested by late term
abortions, weak calves, stillbirths, infertility and characterized mainly by placentas, epididymitis and orchitis. Camels are not known to be
primary hosts of Brucella, but they are susceptible to both B. aborts and B. . They are frequently infected with the organisms, especially when
they are in contact with infected large and small ruminants. Humans can be infected by ingestion of food products such as milk and its products
contaminated with the organism or by direct interaction with an infected animal or by aerosol inhalation. Approaches used to control brucellosis
are immunization-on, test and slaughter of confirmed animals. Moreover, brucellosis in humans represents a major public health hazard, which
affects social and economic development in various countries. The isolation of B. abortus and B. has certainly demonstrated the danger of camel
milk to public health.

Key Words: Brucella, Camel, Prevalence, Zoonosis

9. 1.INTRODUCTION
1.1.background and justification

Camels are even-toed ungulates belonging to the genus which distinguishes two species: the two-humped Bactrian camel (Camelus bactrianus)
and the one-humped Arabian camel (Camelus dromedarius). In many developing countries of Asia and Africa, camels are the most important
source of income for the nomadic population (Abbas and Agab, 2002). Arabian Camels are versatile, vital domestic animals that are best adapted
to harsh environmental conditions prevailing in extreme semi-arid and arid areas. They ensure food security in pastoral communities by
producing milk and meat. They are also sources of hides, which are used as bed sheets; serve as means of transportation and draught power.
Long lactation and ability to maintain milk production over long dry spells are important facets of camel production (Kebede, 2016).
The number of camels in the world is difficult to determine, firstly, because it is mainly an animal of nomadic people and pastoralists who are
moving frequently, and secondly, because camels are not usually subjected to obligatory vaccination. So, an exhaustive census for the camels is
quite difficult. Officially, the total number of camels in the world was around 27 million heads (Faye, 2014).
Camel population is numerous in the arid areas of Africa, particularly in the arid lowlands of Eastern Africa namely, Somalia, Sudan, Ethiopia,
Kenya and Djibouti (Farah et al., 2007). Ethiopia is one of the largest camel populated countries in the world with 1,102,119 numbers of camels
that ranks third in Africa next to Somalia and Sudan, those are kept in the arid and semi-arid lowlands of the Borena, Ogaden and Afar
regions, which accommodate 50% of the pastoralists (Fayera et al., 2015).
Numerous studies revealed that camels are highly susceptible to certain bacterial pathogens such as Bacillus anthracis, Mycobacterium spp,
Clostridium spp, Pasteurella Spp, Salmonella spp, and Brucella spp (Abbas and Agab, 2002). Brucellosis is an infectious disease of domestic and
wild animals with serious zoonotic and economic implications in humans. The disease is an important public health problem in many parts of the
world (Hadush and Pal, 2013). This is mainly manifested by late term abortions, weak calves, stillbirths, infertility and characterized mainly by
placentas, epididymitis and orchitis (, 2016). Camels are not known to be primary hosts of Brucella, but they are susceptible to both B. aborts
and B. . They are frequently infected with the organisms, especially when they are in contact with infected large and small ruminants (Dawood,
2008). In pregnant camels, the bacteria localize in the placenta and are most abundant in abortion material including the fetal stomach, vaginal
discharge and colostrum (Millar and Stack, 2012).
In many countries the infection is on the rise in OWCs due to the uncontrolled trade of live animals (Wernery, 2014). Brucellosis causes heavy
economic losses in camels resulting from infertility, abortions, mastitis, and decreased milk production (Al-Majali et al., 2008). Treatment is
unlikely to be cost-efficient or therapeutically effective because of the intracellular sequestration of the organisms, mainly in the lymph
nodes (Wernery, 2016). Difficulties can arise in diagnosis of camel brucellosis, especially as this disease provokes only few clinical signs in
contrast to its clinical course in cattle (Gwida et al., 2012).
Humans can be infected by ingestion of food products such as milk and its products contaminated with the organism or by direct interaction
with an infected animal or by aerosol inhalation (Kaltungo et al, 2014). Approaches used to control brucellosis are immunization-on, test and

10. slaughter of confirmed animals. Vaccination reduces the number of infected animals and permits disease control (Hadush and Pal, 2013).
Moreover, brucellosis in humans represents a major public health hazard, which affects social and economic development in various countries.
The isolation of B. abortus and B. has certainly demonstrated the danger of camel milk to public health (Bekele, 2004). So, the objective of this
seminar paper is to review available literature on camel brucellosis with its economic and zoonotic importance especially in Ethiopia.
2.LITERATURE REVIEW
2.1 . ETIOLOGY
2.1.1.Taxonomic structure
Brucellosis is the generic name used for the animal and human infections caused by several species of the genus Brucella,. The taxonomic
structure of Brucella is as follows:Domain: Bacteria, Phylum: Proteobacteria ,Class: Alphaproteobacteria,Order: Rhizobiales,Family:
Brucellaceae,Genus: Brucella .( Scholz et al., 2010; 2016; Whatmore et al., 2014)
Within the genus Brucella, there are several recognized species that are pathogenic to animals and human comprised of B. abortus (cattle,
biovars 1–6, and 9), B. (goats, sheep, biovars 1–3), B. (pigs, reindeer and hares, biovars 1–5), B.ovis (sheep), B.canis(dogs) and B.neotomae
(desert woodrats). More recently, new members to the genus include B.ceti and B. pinnipedialis (dolphins/porpoises and seals respectively), B.
microti (voles) and B. inopinata (reservoir undetermined) was identified (Godfroidet al., 2011).
The disease in dromedary camels can be caused by B. abortus, B. Melitensis, B. suis and B. ovis The human brucellosis is caused by bacteria of
the genus Brucella. There are several species that can infect humans, including: Brucella melitensis, Brucella abortus, Brucella suis, Brucella
canis. (Wattam.A,et al. 2009)
Each species within the genus Brucella has unique characteristics and host preferences, with some species being more pathogenic to certain
animals or humans than others. Understanding the taxonomic structure of Brucella is essential for accurate identification, classification, and
research on these important bacterial pathogens.(carreira, et al. 2020)
2.1.2. Physical and biochemical characteristics of camel brucellosis

The physical and biochemical characteristics of camel Brucella, specifically Brucella and Brucella abortus, are similar to other members of the
Brucella genus. Here are some key characteristics:
Physical Characteristics:
Brucella species are small, Gram-negative coccobacilli, which mean they are short, rod-shaped bacteria with a slightly rounded end. They are
typically 0.5-0.7 micrometers in diameter and 0.5-1.5 micrometers in length. Brucella species are non-motile, meaning they do not have flagella
for movement. Some strains of Brucella may produce a capsule that can help them evade the host's immune system.(Dehio, et al. 2017)
Biochemical Characteristics:

11. Brucella species are fastidious organisms that require specific growth conditions, including a rich medium with increased levels of CO2 for
optimal growth. They are facultative intracellular pathogens, meaning they can survive and replicate inside host cells.: Brucella species are
catalase-positive and oxidase-positive. Brucella species are typically urease-positive, producing urease enzymes that hydrolyze urea to form
ammonia.They can utilize a limited range of carbon sources for growth, including glucose and other sugars. Brucella species are nitrate reducers,
converting nitrate to nitrite.(Raghava, et al, 2021)
Brucella are generally susceptible to heat, direct sunlight, acidic conditions and common disinfectants. However, in favorable conditions the
organisms may survive 4 to 6 days in urine, 6 weeks in dust, and 4 to 10 weeks in water, 40 to 75 days in an aborted fetus. They also survive the
production process of soft cheese up to 6 months, in butter up to 4 months, in milk up to 6 months and ice cream up to 30 days. (Kebede,
F.(2000). Moreover, the main species affecting humans are B. abortus (its primary host is cattle) and B. (its primary hosts are goat and sheep),
which cause brucellosis (Khamesipouret al., 2013).
These characteristics help differentiate Brucella species from other bacteria and play a role in their pathogenesis and interactions with the host
immune system. Understanding these physical and biochemical traits is important for the identification and diagnosis of camel brucellosis and
for developing strategies for its control and prevention.(“Brucellosis (Brucella abortus)”, 2022)




Sources: (Wario Waji, and Sultan Abda Neja, (2023)
2.2. Epidemiology
Brucellosis was reported in camels as early as 1931, later, the disease has been reported from all camel-keeping nations (Gwida et al., 2012).
Camel brucellosis can be encountered in all camel rearing countries with exception of Australia. High animal and herd prevalence have been
reported from numerous countries, which not only pose a continuous risk for human infection, but also increase the spread of infection through
uncontrolled trade of clinically inconspicuous animals (Sprague et al., 2012).
Brucellosis in camels is caused by different biovars of B. abortus and B. melitensis (Abbas and Agab, 2002). Though its distribution is worldwide;
yet brucellosis is more common in countries with poorly standardized animal and public health programmes (Capasso, 2002). In Ethiopia,
brucellosis is endemic and the disease is highly prevalent in cattle, camels and small ruminants in pastoral and agro-pastoral areas (Zeru et al.,
2016).
The prevalence of camel brucellosis from different nations may be attributed to changing husbandry and management practices, the number of
affected camels, the virulence of the organisms, absence of veterinary service, presence of reactor animals in the area, lack of awareness about

12. the disease in camels and continuous movement of infected camels into a camel herd (Gwidaet al., 2012). Survival of the organisms in the
environment may also play a role in the epidemiology of the disease (Abou-Eisha, 2000).
Camels play an important role in the epidemiology of brucellosis because the disease may spread through milk (camel milk) especially to those
living in dry and arid zones. A close contact between infected and susceptible camels in a herd promotes the spread of diseases. The camels are
always herded together with sheep and goats and to a lesser extent with cattle and they share the same watering points and pastures, and so it
is not surprising to find a higher incidence of the disease among camels (Teshome et al., 2003).
Theoretically, the three Brucella species known to cause brucellosis in camels (B. abortus, B. , and B. ) can cause infection anywhere. In general,
brucellosis can be found in any season of a year. The epidemic peak occurs from February to July and is closely related to the months associated
with delivery and abortion in animals. Although camels appear to be very susceptible toBrucella infection, isolation ofBrucella organisms from
camel samples is rare. But attempts to isolate Brucella from milk have been successful. B.abortus biovars 1 and 3 were isolated from camels in
Senegal (Wernery, 2014).

2.2.1. Global distribution of camel brucellosis

Brucellosis is a worldwide bacterial disease affecting both animals and humans which subsequently causes serious human health hazards and
economic loss.
Brucellosis was reported in camels as early as in 1931 by Solonitsyn in Russia. Since then, serological evidence of brucellosis has been reported
from the most important camel keeping countries (Fekadu G., Juhar T (2019).
The geographical distribution of brucellosis shows that it is common in countries with poorly standardized animal and public health programmes.
Although it has been eradicated from many developed countries like Australia, Canada, Israel, Japan, New Zealand and Europe),it remains an
uncontrolled problem in regions of high endemicity such as Africa, Mediterranean, Middle East, and parts of Asia and Latin America . Camel
brucellosis is a wide area distributed disease where camel rating is being practiced. It is endemic in countries of the Mediterranean basin, Middle
East, Central Asia, horn of African countries such as Ethiopia, Eritrea,Somalia and Sudan ](Aden Giro et. al(2022).
2.2.2. Distribution of camel brucellosis in Africa

The occurrence of camel brucellosis in sub-Saharan Africa (either prevalence or incidence) is not well documented and reports submitted to the
World Organization for Animal Health (OIE) are largely confined to serological surveys, which are mainly conducted for cattle, sheep, goats and
less for camels. With large pastoral communities, and the demand for meat and livestock products is expected to double by 2050, brucellosis is
expected to pose a major threat to this region(Racloz et al., 2013).

13. According to Ekere et al., 2018, the disease has a cosmopolitan distribution, and affects economically important domestic animals such as camels
including wild life. Persistent cases of brucellosis were observed in most African countries like Tanzania, Nigeria, Uganda, Kenya, Zimbabwe and
Somalia reporting brucellosis in humans and domestic animals such as: cattle, camels, goats and sheep (Racloz et al., 2013).
In East Africa, brucellosis is reported in most member countries of IGAD and endemic with high economic loss and zoonoses (Zewdie and Mamo.,
2018).
In countries with more extensive forms of husbandry practice, such as Chad and Ethiopia, the seroprevalence of camel brucellosis is 3.8% and
5.5% respectively (Wernery, 2014). In Nigeria, the disease has been reported from nearly all camel producing areas (Salisu et al., 2018)
2.2.3. Distribution of camel brucellosis in Ethiopia
Ethiopia has the largest pastoral population of 7 to 8 million where the majorities of these people are living in the Ethiopian Somali and Afar
administrative Region (Fekadu G., Juhar T (2019))Camel population in Ethiopia is around 1.16million, out of which,434,291 inhabits in Afar
region, 353,124 in Somali region and 239,357 in Oromia region (Aden Giro et. al(2022)).. In Ethiopia, brucellosis has been reported in camels
from pastoral areas, where the prevalence was quite vary ranging between 0.73- 11.9% for RBPT and 0.53-9.6% for CFT (Fekadu G., Juhar T
(2019))
Camel production could be a profitable venture for utilizing the vast arid and semi-arid areas of Ethiopia, where other animals survive with
difficulty, especially due to the recurring drought conditions. Under such environmental conditions, camels thrive and form a source of milk and
meat. But, complete exploration of camels for milk and meat production would only be possible when their reproductive performance is
properly understood and improved .In Ethiopia, brucellosis is endemic and the disease is highly prevalent in cattle, camels and small ruminants
in pastoral and agro-pastoral areas (Aden Giro et. al (2022). In Ethiopia, pastoralists used to consume raw milk, which contributes to the
transmission of this disease among human and animals (Fekadu G., Juhar T (2019))
2.2.2. Source of infection and method of transmission
Camels are highly susceptible to brucellosis caused by B. abortus and B. . Consequently, infection of camels depends on the infected animals in
contact with them. Camel-pastoralists keep relatively large flocks of sheep and goats alongside camels. Frequent isolation of B. from camels in
North Africa and Arabia suggests possible active transmission between small ruminants and camels (Abbas and Agab, 2002).
Both vertical and horizontal transmissions exist in animal brucellosis. Horizontal transmission occurs through ingestion of contaminated feed,
skin penetration, via conjunctiva, inhalation and udder contamination during milking. Congenital infection that happens during parturition is
frequently cleared and only few animals remain infected as adults (Bekele, 2004). The primary shedding routes of Brucella organisms remain
uterine fluids and placenta (Saegermann et al., 2010). Camels can be infected via the alimentary tract from contaminated feed or water, via the
respiratory system with contaminated dust or droplets, and via the genital system from infected semen (Khamesipour et al., 2014).
The large herd size, sharing of watering points with ruminants and inadequate hygienic practices under pastoral management system favors
transmission of camel brucellosis, particularly at time of abortion or delivery, by an infected female (Tilahun et al., 2013). At herd level, the risk
factors are herd size and cohabitation with other ruminants (Ghanem et al., 2009).

14. In humans, brucellosis is transmitted by contact with infected animals, consumption of unpasteurized dairy products and undercooked meat,
drinking camel urine including aerosol transmission. For instance, consumption of traditional delicacies such as raw liver can cause human
infection.( Fekadu G., and Juhar T,.2019)

2.2.3. Risk Factor
Management
Management contributes to the transmission of the agent. Once infected, the time required to become free from brucellosis is increased by
large herd size, active abortions and loose housing (Refai, 2002). Calving practices play a major role in the spread of brucellosis. Separate calving
pens minimize exposure of infected animals. There is a positive association between population density (number of animals per land area) and
disease prevalence, which is attributed to increased contact between susceptible and infected animals. Management practices directed at
eliminating infected males and minimizing exposure to aborted tissue greatly reduce the incidence of the disease. Both venereal transmission
and exposure to aborted fetuses and fetal membranes are crucial for maintaining infections in a herd (Banai, 2002).
Host factor
Susceptibility to infection depends on age, sex, breed and pregnancy status of the animals. Younger animals tend to be more resistant to
infection and frequently clear infection, although latent infection does occur. Only 2.6% of animals infected at birth remain infective, as adults
and sexually mature animals are much more susceptible to infection regardless of sex (Abou-Eisha, 2000).
Most animals infected as adults remain infected for life. After reaching sexual maturity, the state of pregnancy has a greater influence on the
degree of susceptibility than age (, 2016).Female animals have essential epidemiological importance not only in susceptibility but also in
disseminating the disease via uterine discharge and milk. The role of males in the spread of disease under natural mating is not important (Abbas
and Agab, 2002).
Agent factors
The organisms are able to survive within host leukocytes and may utilize both neutrophils and macrophages for protection from humoral and
cellular bactericidal mechanisms during the period of haematogenous spread. The inability of the leukocytes to effectively kill virulent B. abortus
at the primary site of infection is a key factor in the dissemination to regional lymph nodes and other sites such as recticulo-endothelial system
and organs such as the uterus and udder (Radostitset al., 2000; Pappas et al., 2005).
Environmental and climatic factor
The survival of the organism in the environment plays a great role in the epidemiology of the disease (Radostitset al., 2000; McDermott and
Arimi, 2002). Atmospheric conditions and seasons of the year may have influence on the management and contact of the infected and
susceptible host and hence in dry areas, water resources are sparsely distributed. As a result, the congregation of a large number of mixed

15. ruminants at water points facilitates disease spread. The coincidence of parturition in the wet season enhances the viability of the organisms in
the environment, thus increasing the chance of infecting susceptible animals (Kebede, 2016).
2.2.4 Immune response
Once the Brucella organism enters the body of the animal and causes infection, a humoral and cell-mediated immune response is induced during
Brucella infection. The magnitude and duration of these responses can be affected by many factors including virulence of the infecting strain,
size of inoculum, age, sex, pregnancy, species, and immune status of the host. Although humoral immune response plays an important role in
immunity to Brucella, it is the cell-mediated response that is most important in providing protection [Pappas, 2010).
Humoral immune response
IgM is the first immunoglobulin produced after initial strain 19 immunization, followed by IgG. IgG1 is the most abundant and its concentration
exceeds that of IgG2. Age at immunization and number of organisms administered affect the antibody response magnitude and duration. After
standard dose immunization, IgG antibody concentrations decline to diagnostically insignificant levels over 3-6 months, with residual antibody
predominantly IgM. A minimum dose may take 2-7 months to develop "reactor" titres, while a large dose produces significant agglutinin titre in
2-4 weeks. Most infected animals develop a diagnostic agglutinin titre 30-60 days after exposure, but there is a great variation in response from
animal to animal. Infected animals may not produce IgG antibodies until parturition, making it difficult to differentiate from non-infected
vaccinated animals. IgM is the most efficient antibody in the tube agglutination test, while IgG1 has the capacity to block agglutination by other
isotypes (WHO, 1998).
Cellular immune response
Brucella bacteria produce antibodies to survive in macrophage cells. Virulent strains of Brucella can survive in normal macrophages for long
periods, making recovery from infection dependent on increased bactericidal activity of phagocytic cells. T-lymphocytes release lymphokines to
activate macrophages. (Jones, et al 1992)
Brucella antigens recognized by T-cells stimulate antibody release. Cell-mediated immunity is induced by live organisms capable of establishing
persistent intracellular infection and certain types of antigens. The role of cytotoxic cells in the immune response to Brucella is unknown. More
studies are needed to understand protective immunity to Brucella [Pappas, 2010)
2.3. Pathogenesis
The pathogenic potential of Brucella species is highly dependent on its ability to enter and survive within host cells. The initiation of Brucella
infection depends on exposure dose, virulence of the Brucella species and natural resistance of the animal to the organisms (Radostitset al.,
2000).
The Brucella organisms have the ability to persist and replicate within phagocytic cells of the reticulo-endothelial system as well as in non-
phagocytic cells such as dendritic cells macrophages and trophoblasts (Kaltungo et al., 2014).

16. Brucella Spp Can enter the body through the lungs, the digestive tract, mucous membranes, and intact skin. Brucella has a predilection for
the gravid uterus, udder, testicles, accessory sex male glands, lymph nodes, joint capsule and bursa. After initial invasion of the body, localization
occurs initially in the regional lymph nodes draining the area before spreading to other lymphoid tissues including the spleen, mammary and iliac
lymph nodes (Wanjohi, 2014).
Resistance to infection is based on the host’s ability to prevent the establishment of infection by the destruction of the invading organism. The
inability of the leukocytes to completely kill virulent Brucellaat the primary site of infection is a key factor in the dissemination to the regional
lymph nodes, the reticulo-endothelial system and other organs such as uterus and udder (Wanjohi, 2014).
Survival of the first line of defense by the bacteria results in local infection and the escape of Brucella from lymph nodes into the blood (, 2016).
Once in the bloodstream, the organism disseminates to multiple organs, thereby displaying an affinity for reticulo-endothelial tissues, such as
liver, spleen, the skeletal and hematopoietic system (Greenfield et al., 2002).After the Brucella organisms spread through the haematogenous
route in females it also reaches the placenta and then to the fetus (Lapaque et al., 2005).
In a pregnant uterus, multiplication of the bacteria is supported by the presence of the sugar alcohol, erythritol, which is a fetal product
concentrated in the chorion and cotyledons (Kaltungoet al., 2014).During the acute phase of infection, the semen contains large number of
Brucella as the infection becomes more chronic, the number of organisms excreted decreases and excretion may cease altogether. However, it
may also continue to be executed for years or just become intermittent (Radostits et al., 2000).
Little is known about the pathological changes in camels. Gross lesions may be found in the predilection sites uterus, udder, testicles, lymph
nodes, joint bursa and placenta. Hydro bursitis was often observed in brucellosis positive dromedaries causing swelling of the bursa (Werney and
Kaaden, 2002).
2.4. Clinical Manifestations
Camels are silent carriers of the disease as clinical signs of brucellosis in camels seem to be very rare (Kaltungo et al., 2014). According to various
researchers, the clinical signs of brucellosis in breeding camelids are the same as those in bovines and small ruminants, although infection in
breeding camelids causes fewer abortions than it does in bovines and small ruminants (Wernery, 2016).

The primary clinical manifestations of brucellosis in animals are related to the reproductive tract. Abortion that occurs in the last trimester is
the most obvious manifestation. Infection may also cause stillbirth or weak calves, retained fetal membrane, lowering of fertility with poor
conception rates and reduced milk yield (Kebede, 2016). Non pregnant dromedaries experimentally infected with a field strain of B. abortus
developed only mild, transient clinical symptoms including reduced appetite, slight lameness and bilateral lacrimation (Gwida et al., 2012). In
male camels, inflammation and enlargement of the epididymis, characterized by hyperplasia, degeneration of tubular epithelium, orchitis and
inflammation of other accessory sex organs are common (Kebede, 2016). Hydro bursitis was often observed in brucellosis positive dromedaries
causing swelling of the bursa (Werney and Kaaden, 2002).
2.5. Diagnostic Methods

17. Diagnosis of brucellosis is the cornerstone for any control and eradication program. Especially in humans due to its heterogeneous and poorly
specific clinical symptoms the diagnosis of brucellosis always requires laboratory confirmation. The clinical signs are not pathognomonic for
brucellosis, although the herd history may be helpful in diagnosis. A combination of growth characteristics, serological, bacteriological and or
molecular methods should be practiced (Hadush and Pal, 2013).
The gold standard test for brucellosis is based on isolation and identification of the causative bacterium by culturing. However, this requires
skilled personnel in a standard biosecurity laboratory (Nielsen and Yu, 2010). Although several PCR assays have been developed, serological tests
are still frequently used as diagnostic methods. The most commonly used serological tests are the RBT, CFT, and ELISA (Al Dahouk et al., 2002).
2.5.1. Bacteriological method

Isolation and identification are the most reliable techniques in the diagnosis of brucellosis, even though not always successful, and represent a
major infection risk for technicians (Ghorbani et al., 2013). Microbial culture may be used for several suspected cases, nonetheless is not used
for surveying the disease in the camel populations (Khamesipour et al., 2014).
The most valuable samples include aborted fetuses (stomach contents, spleen and lung), fetal membranes, vaginal secretions (swabs), and milk,
semen and arthritis or hygroma fluids. From animal carcasses, the preferred tissues for culture are those of the reticulo-endothelial system (i.e.
head, mammary and genital lymph nodes and spleen), the late pregnant or early post parturient uterus, and the udder (OIE, 2009).
Recovery of Brucella species from camel specimens requires rapidity in processing of samples; there is increased difficulty in isolation of the
organisms with storage of samples (, 2016). For isolation, the recommended medium is Farrell’s medium, which contains six antibiotics. But
other selective Brucella media are also in use for the growth of this pathogen from fresh camel milk and camel tissue samples (, 2016).
A nonselective, biphasic medium, known as Castaneda’s medium, is recommended for the isolation of Brucella from blood and other body
fluids or milk, where enrichment culture is usually advised (OIE, 2009). Specimens of fetal stomach, lung, liver, placental cotyledon, vaginal
discharges, are stained with Gram stain and modified Ziehl Neelsen stains. Brucella appears as small red-colored coccobacilli in clumps (Quinn et
al., 2002).
2.5.2. Serological Methods

A definitive diagnosis of Brucella infection requires simultaneous application of different laboratory techniques due to the lack of a single, highly
reliable diagnostic method (Gyuraneoz et al., 2011). Although serological techniques of brucellosis have been used for detection of brucellosis in
camels, they are neither sufficiently sensitive nor specific as a result of an inadequate immune status of the host (Gwida et al., 2011). There is
no single serological test by which a bacterium can be identified as Brucella. However, it was found that a combination of different serological

18. tests can increase diagnostic efficacy in camels, although none of the serological tests can differentiate between a B. abortus or B. Bovis
infection (Wernery, 2016)
Rose Bengal Plate Test

The RBPT is a commonly used screening test for Brucella agglutinins in animals and humans. It is a modification of the acid-plate agglutinin test,
employing a suspension of B.abortus organism stained with Rose Bengal dye and buffered at pH 3.65. Sera showing positive reactions are then
subjected to further tests such as the serum agglutination test (SAT) or complement fixation test (CFT) to provide quantitative titres (Mohamed,
2015) .RBPT is commonly used to detect certain levels of antibody produced against Brucella organism present in serum, semen and milk in a
chronic disease. The serum may contain varying levels of antibodies in the form of IgM, IgG1, IgG2 and IgGA at different stages of infection
(Onunkwo, 2005).
Complement Fixation Test

This test is regarded throughout the world as being the confirmatory test for the serological detection of infected animals. It detects
predominately IgG antibodies as most of IgM ones are destroyed during serum deactivation; this is why it is used as a confirmatory test (Kebede,
2016). The test distinguishes reactions caused by other factors like vaccines and other bacterial infections. Many authors regard the CFT as being
the most sensitive and specific test for brucellosis because CFT antibodies remain in the serum for longer than SAT antibodies (Wernery, 2016).
Enzyme Linked Immunosorbent Assay
Other researchers have used ELISA for the detection of Brucella antibodies, not only in camel sera, but also in camel milk. The camel milk ELISA
seems to be an important alternative to the conventional diagnosis of camelid brucellosis (Wernery, 2016). The RBT was suitable for screening
camel sera for brucellosis, but the c-ELISA detected 2.1% more positives. Recently, ELISA has been used not only detecting Brucella antibodies in
sera but also in camel milk antibodies in sera but also in camel milk (Van Stratenet al., 1997).
Milk Ring Test

Milk Ring Test is used to detect antibodies in milk. The development of a positive reaction is dependent on two reactions (i) fat globules in the
milk are aggregated by milk antibodies (fat globule agglutinins) and (ii) Stained Brucella cells (antigens), which are added to the milk, are
agglutinated by the Brucella antibody fat globule complexes which rise to form a coloured cream layer at the top (Pappas, 2010).
In contrast to cattle milk, camel milk cannot be used to detect lacteal brucellosis antibodies using the MRT, because camel milk lacks the
agglutinating substance required to cluster fat globules. It is also known that camel milk fat globulins are tiny micelles which, therefore, do not
cream up to produce a surface fat layer (Wernery, 2016).

19. A new method is established called modified milk ring test in camels by adding Brucella negative cow milk to camel milk. Then after, the authors
observed a typical colored -my ring in brucellosis positive samples. Non-specific reactions are common with this test, especially in brucellosis
free areas (Van Straten et al., 1997).
2.5.3. Molecular method
Polymerase chain reaction (PCR)

Molecular technologies like PCR is a new approach and applied in many diagnostic works to overcome limitations and difficulties in bacterial
culture and serological assays (Radostits et al., 2000). The PCR is a sensitive, fast, and relatively cheap method and is mainly useful in the
detection ofBrucella DNA in tissues and body fluids contaminated with non-viable or a low number of the organism. There are few publications
on using PCR in the detection of camel brucellosis. The PCR is more reliable than serological tests but its efficacy remains highly variable
(Khamesipour et al., 2014). This is a very reliable diagnostic tool, which can even differentiate between B. and B. abortus (Alshaikh et al., 2007).
2.6. Treatment

As a general rule, treatment of Brucella infected animals is not recommended because of the high treatment failure rate, cost, and potential
problems related to maintaining infected animals in the ongoing eradication program. As a result treatment is unlikely to be undertaken in
animals and no economically feasible drugs. However, a dose of 100mg of broad long acting tetracycline given every 3 days for a period of 6
weeks achieved to cure 75% of cases (Hadush and Pal, 2013).
Ox tetracycline and streptomycin are capable of penetrating the bacterial cell wall, inhibiting protein synthesis and providing long lasting
concentrations in the plasma and hence considered most effective in the treatment of brucellosis (Kushwaha et al., 2014).
A combination of Quinolones and rifampicin also has given good results (Radostits et al., 2000). Using antibiotics may be a way to save valuable
animals (e.g. racing camels) from being culled, but it is doubtful if antibiotic treatment on a herd-level basis can be successful (Wernery, 2016).
2.7. Zoonotic importance
Brucellosis is an important zoonotic disease of public health implications accounting for more than 500,000 human cases per annum worldwide
(Seleem et al., 2010). The burden of the disease is enormous but yet remains under-prioritized globally especially amongst the pastoralists and
small-scale livestock farmers. Brucellosis is primarily a disease of animals and is transmitted directly and indirectly to human cases (Hadush and
Pal, 2013).

Most cases of human brucellosis are caused by ingestion of unpasteurized dairy products or meat from infected animals and close contact with
their secretions. Camel keepers consume camel milk as well as liver without heat treatment. This is even considered a delicacy. There is also a
close contact between herdsmen and the animal during watering, grooming, riding, nursing sick ones and delivery assistance (Bekele, 2004). The

20. situation is even worse as farmers from rural areas think that raw camel milk has a healing effect on the digestive system (Khamesipour et al.,
2014.)
From a public health point of view point, brucellosis is considered to be an occupational disease that mainly affects farm laborers,
slaughterhouse workers, butchers, shepherds, laboratory workers and veterinarians (Yagupsky and Baron, 2005; Behzadi and Mogheiseh, 2011).
With the development of commercial camel dairies in several countries, this disease should be seriously considered because of its impact on
human health. Unfortunately, till now, there are no studies on vaccination or eradication strategies of camel brucellosis (Tibaryet al., 2006).As
compared to study of animal brucellosis, study of human brucellosis in Ethiopia is sparse with even less information on risk factors for human
infection (Yohaneset al., 2013).
Malta fever caused by B. was detected in 30% of camel milers and handlers on a large camel farm in Riyadh, Saudi Arabia. The abortion rate on
the farm reached 12% and B. biovars 1, 2 and 3 were isolated from aborted camel fetuses (Gwida et al., 2012). Five out of the nine known
Brucella species can affect humans and the most pathogenic and invasive species for humans is B. Melitensis followed in descending order by B. ,
B. abortus and B.canis (Acha Szyfres, 2003).
Transmission in humans is principally by contact with materials such ascarcasses aborted fetuses, placentas, vaginal discharges, manure, semen
and urine. Man to man transmission is very rare. Other routes of infection in man include inhalation of air droplets containing the organism.
Accidental self-inoculation with strain 19 of B. abortus vaccine (Sati, 2002).
Pastoralists in endemic areas are at high risk of infection by Brucella species (Skalskyet al., 2008). Human brucellosis is a chronic and debilitating
disease that may be presented with variable clinical signs (Kaltungo et al., 2014). The common clinical symptoms include weakness, lethargy,
chill, fever, sweating, decreased appetite, arthralgia, myalgia, weight loss, headache, back pain and psychological symptoms (Mariyo and Obey,
2016).
As humans are considered end hosts of B. abortus associated with a moderately severe infection, known as “undulant fever”, and B. , B. canis
and B. cause the much more severe disease known as “Malta fever” (Quinn et al., 2002). The incubation period for brucellosis is typically 2 to 3
weeks, but can vary from 5 days to more than 5 months. Acute infection can be unrecognized and can result in chronic infection with symptoms
recurring years later (Saleem et al., 2010)In humans, diagnosis of brucellosis is always missed, because other diseases that partially or almost
totally mimic brucellosis symptoms including malaria, typhoid, paratyphoid and influenza are misdiagnosed. Direct bacteriological and molecular
methods and indirect serological tests are used for brucellosis diagnostics (Smirnovaet al., 2013).But the definitive diagnosis is by culture or
serology. Sometimes Brucella species can be isolated from blood and bone marrow early in the infection. Occasionally, they can be recovered
from CSF, urine or tissues. In addition, Brucella species can be isolated from a variety of plain or selective media such as Farrell`s medium or
Thayer-Martin modified medium (Kebede, 2016).
In the acute form of brucellosis, sensitivity of blood cultures has been reported more than 80%. However in the chronic form, sensitivity has
been recommended 30%-70% (Espinosa et al., 2009). The zoonotic potential of the disease in camels should not be overlooked, despite; the
advances made in surveillance and control, the prevalence of brucellosis is increasing in many developing countries due to various sanitary,
socioeconomic, and political factors (Pappas et al., 2006).

21. 2.8. Socio Economic Importance

Brucellosis is characterized by abortion, non-viable offspring birth in females, and orchitis and epididymitis in male animals. Abortion is the
major feature that is manifested in camels. The disease is also associated with infertility and prolonged calving intervals, and has considerable
impact on camel production. Chronic inflammation of epididymis, of the joints, tendon sheath and synovial bursae especially at the carpus may
also occur in camels (Abbas and Agab, 2002). The disease can generally cause significant loss of productivity through late first calving age, long
calving interval time, low herd fertility and comparatively low milk production, as in cattle may also happen in camels. The disease can also have
an impact on export and import of animals constraining livestock trade (Bekele, 2004).

The disease can generally cause significant loss of productivity through late first calving age, long calving interval time, low herd fertility and
comparatively low milk production, as in cattle may also happen in camels (Radostits et al., 1994). The disease can also have an impact on export
and import of animals constraining livestock trade. Afzal and Sakkir (1994) have suggested that subclinical brucellosis can pose problems in
racing camels by reducing the performance and productivity of these animals in the Arabian Peninsula where camel racing is highly popular.(Xie,
B. 2023).
The economic losses encompass cost of treatment of affected individuals and long term debilitation that renders the individual unproductive.
The chronic nature of the disease and the difficulties arising when treating patients must also be taken into consideration when calculating costs
to local health services (McDermott et al., 2002).

2.10. Prevention and Control of the Disease

Brucellosis was eradicated in Europe, Australia, Canada, Israel, Japan and New Zealand, but it remains uncontrolled in Africa, some parts of
Middle East, Asia and Latin America. Regrettably, until now, there are no studies on eradication strategies or vaccination of camel brucellosis
(Khamesipour et al., 2014).
Brucellosis, due to B.abortus, B. and B. , creates an important human health threat in many parts of the world. Hence, development of safer and
more efficacious candidate vaccines alone, or increased emphasis on other regulatory programme components, could have enormous impacts
on mitigating the worldwide prevalence of brucellosis and the associated zoonotic infections (Olsen et al., 2010). The choice of control strategy
depends on a number of considerations, such as infection prevalence in different animal species, human clinical incidence and the capacity of
Veterinary Services. However, a prerequisite for any control programme is the implementation of an efficient animal disease surveillance
network (Smits, 2013).

22. The control of camel brucellosis should be tailored to suit conditions in the particular countries where camels are raised. Most of these countries
are poor and nomadic tribes raise camels. Even though, prevalence of camel brucellosis is low, the positive animals may serve as future foci of
infection, leading to low productivity, posing a public health risk and lowering the market value of camels (Khamesipour et al., 2014).
In OWCs, both inactivated and attenuated Varicella Vaccines have been used successfully. Dromedaries were vaccinated with B. abortus strain
S19 and with B. Rev 1. Very little is known about the optimal vaccination age in camels and their serological response. An eradication campaign
in camelids may also be based on vaccination and ‘test and slaughter’ policy for dairy herds and ‘test and no breeding’ for racing herds. Camel
calves should be vaccinated at 4–8 months of age, using a full adult dose of vaccine (Abbas and Agab, 2002).
Adult camels vaccinated by live attenuated B. abortus S19 and B. Rev-1 proved to be effective vaccines against the disease in camels and other
ruminants. Both vaccines have disadvantages of causing abortion, being pathogenic to human beings and interference with serological tests had
detectable antibodies up to 3 months post-vaccination(Wernery and Kaaden, 2002; Abbas and Agab, 2002).
Vaccinations alone would not suffice for success. The main approach in a long term control strategy of brucellosis is to vaccinate only female
replacement camels less than 1 year old (maturity in OWCs begins with 4 years). This strategy will after several years establish an immunized
herd and will not induce abortions and excretion of the vaccine strain through milk. It will also protect these herds from brucellosis threat by
surrounding positive sheep and goat farms. The best way to halt the spread of the disease is to castrate serologically positive bulls, never breed
positive females and start vaccination in positive herds, especially when they are used for dairy (Wernery, 2016).
Moreover, camel brucellosis should be included in national programs for the control and eradication of brucellosis in endemic nations. So,
individuals working with these animals should be aware about the risk of camels as a source of brucellosis. Precautions should be taken to avoid
contamination of the skin, as well as inhalation or accidental ingestion of organisms when assisting at a birth, performing a necropsy, or
butchering an animal for consumption (Kebede, 2016). Introduction of hygiene procedures and correct disposal of aborted materials and the use
of disinfectants is also necessary (Al-Majali et al., 2008).
Eradication in small ruminants has never been achieved and may also be very difficult to achieve in OWCs due to the complexity and expense of
treating animals across widespread areas (Smits et al., 2013). Control of camel brucellosis should be a must for nations where camels are
raised.Vaccination of uninfected animals is conventionally considered as the most effective and economical means of defending farm animals
against brucellosis (Khamesipour et al., 2014).
2.11. Knowledge, attitude and practice of population towards camel brucellosis
Brucellosis is a zoonotic disease caused by bacteria of the genus Brucella. Camels are known to be reservoirs of Brucella abortus biovar 3, which
can cause brucellosis in humans. In Ethiopia, camels are an important livestock species, and brucellosis is a major concern for both animal and
public health.(Hussein, and M. F. 2021) . Studies in Ethiopia have shown that knowledge of camel brucellosis among camel owners and handlers
is generally low. Many camel owners are unaware of the disease, its symptoms, and its zoonotic potential. This lack of knowledge contributes to
the spread of the disease and poses a risk to human health.(Gutema, et al 2021)

23. Camel owners and handlers in Ethiopia generally have a positive attitude towards camel brucellosis control. They are willing to participate in
control programs and adopt preventive measures. However, some traditional beliefs and practices, such as consuming raw camel milk, can
hinder brucellosis control efforts.(Dadar,et al,.2020)
Brucellosis control practices among camel owners and handlers in Ethiopia are often inadequate. Vaccination is the most effective way to
prevent brucellosis in camels, but vaccination coverage is low. Other control measures, such as proper disposal of aborted fetuses and isolation
of infected animals, are also not widely practiced. Brucellosis is a major zoonotic disease in Ethiopia. Human cases of brucellosis have been
reported in several parts of the country, particularly in areas where camels are kept. The consumption of raw camel milk and contact with
infected camels are the main risk factors for human infection. (Tulu, et al. 2020)
Brucellosis is a significant zoonotic disease in Ethiopia, and camels are an important reservoir of the bacteria that causes it. Knowledge of camel
brucellosis among camel owners and handlers is generally low, and control practices are often inadequate. This poses a risk to both animal and
public health. There is a need for increased awareness and education about camel brucellosis, as well as improved control measures, such as
vaccination and proper disposal of aborted fetuses.(Abebe, et al. 2017)
2.12.Conclusion and recommendations
Camels in Ethiopia are essential for pastoralists, but their productivity is affected by various diseases, including Brucellosis. The disease's
prevalence is on the rise globally and requires urgent intervention to prevent further spread. Brucellosis has severe consequences for both
animal and human health, and eradication can only be achieved through control, prevention, and surveillance. Risk factors for the disease
include age, parity, herd size, and inadequate vaccination. Awareness campaigns, vaccination programs, and establishment of suitable
laboratories are recommended. To minimize occupational and public health risks, people should avoid consuming unpasteurized dairy products,
and proper disposal of aborted fetuses and contaminated materials is necessary.
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