Review on the Epidemiology, Public Health Importance and Status of Awareness of camel rearing pastoral communities of Ethiopia on camel tuberculosis

Ethiopia is one of the country known by rearing different species of animals and it is believed to have the largest livestock population in Africa [1]. From different species of animals rearing in Ethiopia, Dromedary camel (one-humped Camelus dromedarius) is the principal one. Out of the 28 million global population of domesticated large camelids (dromedaries and Bactrian) 4.8 million Dromedary camels are found in Ethiopia [2,3].


Introduction
Ethiopia is one of the country known by rearing different species of animals and it is believed to have the largest livestock population in Africa [1]. From different species of animals rearing in Ethiopia, Dromedary camel (one-humped Camelus dromedarius) is the principal one. Out of the 28 million global population of domesticated large camelids (dromedaries and Bactrian) 4.8 million Dromedary camels are found in Ethiopia [2,3].

Most of camel population in Ethiopia is kept by pastoralists
where nature is cruel and shortage of water and feed resource is there. Camels occupy practically all fringe drier lowland areas that generally fall below 1,500 meters above sea level [4,5]. The pastoral areas of Ethiopia is known by a camel culture, a monoculture that is communicated as an adjustment to dry environment through reliance on the camel dependent on uniform farming strategies and portability [6]. In Ethiopia, camels are mostly raised in Afar, Somali and Oromia (Borena and Kereyu) regions [7]. Guji and west Guji drier areas, pastoral communities are following the tried-and-tested adaptation strategy of camels and goats which one is more resilient more

Abstract
In the pastoral areas of Ethiopia, camel is the spine for their everyday life and extraordinarily adjusted to cruel condition. In Ethiopia, camels are for the most part raised in Afar, Somali, and Oromia (Borena, Kereyu and Guji). The pastoral community utilized camel products, such as milk and meat, and they used camels for various purposes for example, for transportation, draft, ploughing land, festivity and rivalry as in dashing. In the pastoral areas of Ethiopia, camel milk is accepted as treatment for gastritis, asthmatics, stomach inconvenience, HIV, hamot (kar), tuberculosis, fever, urinary issues and hepatitis. Camels have high contribution in Economic development of the country. In spite of having such like various purposes for pastoral areas, a few ailments infl uence the wellbeing status of camel. From signifi cant illnesses, tuberculosis is one of the principal, which infl uence the camel Health and have a zoonotic impact. Camel tuberculosis is chronic diseases, which is portrayed by the development of granulomas, essentially in the respiratory tract, and related lymph nodes, from which the mycobacteria are discharged and contaminate other susceptible animals. Camel tuberculosis has general public health implication, especially in pastoral areas of Ethiopia due to the communities have the habit of consuming raw camel milk and its products and they do have consistent or day-by-day contact with their camels. In addition to this, the etiological agents are transmitted to humans through aerogenous route from those animals with active cases in the herd. The infection has been reported from several parts of pastoral areas of the country essentially dependent on tuberculin tests and abattoir inspections. Therefore, attention should be given towards the control of tuberculosis in livestock; public health education on zoonotic importance of the disease or awareness creation and the national tuberculosis control needs to consider the one health approach and further epidemiological studies should be undertaken. expanded because of various purposes. Presently days a few people in Ethiopia mindful of that, the camel milk holds distinctive compound parts inside it which make it one of a kind from other dairy animals and help the customer for various medical advantages. As indicated by various authors the camel milk comprises of: fi nely homogenized fat, various kinds of proteins, for example, casein, whey and insulin, carbohydrate, minerals, vitamins and electrolytes [14][15][16].
In view of the segments of various synthetic compounds or because of various bioactive segments in camel milk individuals utilized as a treatment for various illnesses. The individuals which live in Babilie and Kebribeyah districts, Jijiga Zone of the Somali Regional State they utilized camel milk as treatment of gastritis, asthmatics, stomach inconvenience, HIV, hamot (kar), tuberculosis, fever, urinary issues and hepatitis. In addition, it is used to treat various diseases such as jaundice, malaria, constipation, to clear the stomach, baby blues care of ladies, to detoxify snake venom and fart, intestinal sickness and blockage for reason that camels peruse on different plant species and dynamic specialists with helpful properties from these plant species are discharged into the Milk. Pastoralists considered camel milk as prepared available medication for various sicknesses [17][18][19].
The children want to drink camel milk as opposed to other dairy animals' milk. Camel milk have had stunning upgrades in their behaviour and diets [15]. The lactose substance of camel milk (4.8%) is practically like human mother's milk and in this manner can be readily digested by people experiencing lactose prejudice that implies tit fi ll in as treatment for allergy [20].
In addition to camel milk, camel meat also a signifi cant source of animal protein in many African and Asian countries, especially in areas where the climate adversely affects the production effi ciency of other animals. The culinary and cooking practices, as well as the palate for meat, in several African and Arabian countries have evolved toward camel meat to other meat animals' species in light of convictions in restorative advantages, its accessibility as well as moderate cost [21]. Camel meat is more benefi cial contains less fat as well as less levels of cholesterol in fat than other meat animals.
Compared to beef, camel meat is also comparatively high in polyunsaturated fatty acid giving opportunity for reducing the risk of cardiovascular disease, which is related to saturated fat consumption. Camel meat is also used for remedial purposes for diseases such as hyperacidity, hypertension, pneumonia, and respiratory disease [22].
In building up the economy of the country the camels has an essential role. As per NBIIA [23]. Ethiopia earned USD 211.1 million during Ethiopian fi nancial year (July 2010-June 2011) by sending out 16,877 tons of meat and 472,041 head of live animals. According to the information accessible with Ethiopian Revenue and Customs Authority, live animals trade contributed 70% of the profi t while the parity (30%) was gotten from meat send out. Of the quantity of traded live animals, camel represented 13% and contributed 25% to the income produced. As Mehari, et al. [24], report in Somali area camel milk sale was the main sources of income, and there are various camel milk assortment focuses selling milk in nearby towns and urban areas of the Somali district of Ethiopia, just as traded to the neighbouring nation of Somaliland [25]. In addition, in Meiso (Oromia) lowlands of Ethiopia, the majority of pastoralists (78%) had been selling camel milk [26]. Milk selling is the job of women in Afar, and this is comparative in the Somali district of Ethiopia where it was customarily and predominantly promoted by women and their associations along connection lines [18].  [27][28][29][30].
In addition to the above pathogens, Tuberculosis a genuine rising sickness in camels of various African countries, especially in Ethiopia. As researchers reviled that, in Ethiopian abattoirs a predominance of up to 10% was recorded dependent on the recognizable proof of gross lesion in apparently healthy dromedaries [31]. The other research as of late show that, the prevalence of camel tuberculosis in Akak abattoir in central Ethiopia report that 9.82% [32]. Few researchers also conducted different research in different pastoral areas of Ethiopia, which indicate different prevalence rate of camel tuberculosis [31,33,[34][35][36][37].
Tuberculosis diseases circulate between human and animals. So that it do have a serious a zoonotic and reverse zoonotic importance. In Ethiopia had also confi rmed transmission of M. tuberculosis from farmers to their cattle, goat and camel [38,39,34,40]. The M. tuberculosis strain isolated from disseminated TB lesions in a camel belongs to the E-A lineage (SIT 149), a dominant strain in Ethiopia [34,41].Therefore, in Ethiopia M. tuberculosis seems to be more The name "Tuberculosis" comes from the nodules, called 'tubercles', which form in the lymph nodes of affected animals [45]. The genus Mycobacterium of the family Mycobacteriaceae includes non-motile and non-sporing acid-fast rods of various lengths [46]. Mycobacteria are generally not species-specifi c pathogens [47].
Mycobacteria possess a waxy coat that makes it diffi cult for the host's defence mechanisms to destroy them and results in a slow chronic disease [48]. So that Tuberculosis (TB) is, a chronic, reportable gran ulomatous zoonosis caused by Mycobacterium tuber culosis complex and affects many animal species including camels [49,50].

Classifi cation of mycobacterium
The genus Mycobacterium includes diverse species ranging from environmental saprophytes and opportunistic invaders to obligate pathogens differing in their nutritional requirement [51].

The Mycobacterium Tuberculosis Complex (MTBC)
The mycobacteria assembled in the MTC are characterized by 99.9% similarity at the nucleotide level and identical 16S rRNA sequences but differ widely in terms of their host tropisms, phenotypes, and pathogenicity. Suggesting that they all derived from a common ancestor [52][53][54] microti are the causative agents of TB in animals, and can be transmitted to humans. [57][58][59].
The host range of M. bovis is considered the broadest of the complex, causing sickness over an assortment of animals.
It could be normal that the major evaluative movements associated with adjustment to various hosts would have involved huge microbiological separation [57,59]. The different bacterial species show a certain host tropism. E.g.
M. bovis most commonly affects cattle, M. tuberculosis affects humans, M. microti is most frequently isolated from voles [53].
Nevertheless, spill over to other hosts has been observed for most of the bacteria [55,60,61].

The Non-Tuberculous Mycobacteria (NTM)
Mycobacterium species other than the MTBC that cause TB like diseases in man and animals are commonly called nontuberculous mycobacteria (NTM) or "atypical mycobacterium" [51,62]. Non-tuberculous mycobacteria are ubiquitous organisms with nearly 100 different species found in soil and water [63]. Some of the species including in this member are Atypical mycobacterium are not pathogenic to man and animals except in certain situations such as direct inoculation into wound or introduction into immune compromised hosts due to immune suppressive therapy or due to HIV infection [62]; however, they are important during diagnosis as they sensitize man/animals to tuberculin test [58,62]. In addition, NTM exerts a challenge in microscopic diagnosis of MTBC, it cannot differentiate MTBC from NTM particularly M. chelonae as both of them have similar chording feature under microscopy, which can cause a misidentifi cation problem [64].

Epidemiology of camel tuberculosis
In Ethiopia, there is little published information on the epidemiology of camel tuberculosis. The ailment infl uences camels all through the globe, incorporating camels raising in pastoral areas of Ethiopia. In 1991, Abdurahman & Bornstein [69], detailed the malady to be moderately uncommon in Somalia; a nation around then had perhaps the biggest population of OWCs on the world [70]. At that point after hardly any studies have been directed in the epidemiological investigation of Tuberculosis and recognizable proof of the causative agents in camels [31,33,35].
The study, which is done by Beyi, et al. [37], at abattoir of Eastern Ethiopia was to recognize M. Bovis in dromedary as causative agent of Tb. The prevalence of camel shows that 33 non-MTBC species [38]. These discoveries not just recommend the signifi cance of non-MTBC in OWC TB in Ethiopia, yet in addition feature a potential role for OWCs in the transmission of M. tuberculosis in people [2].
As of late Yasmin, et al. [32], reveal 9.82% of camel tuberculosis at Akaki abators and the origin of camels were from Borana and Metehara. The camels which origin from Metehara shows high prevalence which 9.6% and 10.94% from Borana respectively. The single intra-dermal comparative cervical tuberculin (SICCT) test of the 387 camels indicated that overall positive tuberculin reactor prevalence of 9.82% (38/387) Prevalence of camel tuberculosis recorded by Mamo et al. [31], with abattoir-based prevalence of 10.4% in Akaki and again [46] report the prevalence of 5.1% at Dire Dawa, and Gumi et al. [34], also reports 3.1% for camels in Southern Ethiopia.
Similarly, some other authors at different sites in Ethiopia [36,37] for camels at Akaki and Eastern part of Ethiopia. In Ethiopia dromedary camels, M. bovis [33] and M. tuberculosis from tissue lesions [34,35]  Strains of M. tuberculosis have also been identifi ed from camels in southern Ethiopia [34], from camels in Eastern Ethiopia [35], from goats in Afar by Mulugeta, et al. [74], from pigs in central Ethiopia. There are various methods of spread of tuberculosis between Camelid herds under intensive management system. This is mainly occurred when infected animal is introduced into non-infected herd [77]. Animal with pulmonary lesions will discharge the organisms in breathed out air that can act as source of infection in those non-infected animals [78].

Source of infection and mode of transmission
Camels under nomadic environment, they can get the disease by various systems. Camels under migrant condition, they can get the disease by various systems. A portion of the animals can secure the contamination when they interact with infected animals (camels or cattle). There is likewise other approach to get the sickness; for example in the areas where dromedaries meander uninhibitedly in the desert during day and come back to their comps in night; they can without much of a stretch have contact with discharges of desert gazelles from which they gotten the disease. Several authors have announced tuberculosis in gazelles of the Arabian Peninsula [79]. It is likewise deserving of notice that dromedaries are coprophagus Animals and this this habit can expose them to the infectious agents.
Zoonotic infections, transmissible between humans and animals, are closely associated with pastoralists, because of their close contacts with their domesticated animals [80,81].
In Ethiopia, the signifi cant routes of transmission from camel to individuals are probably going to be through utilization untreated milk and meat items from infected animals, but also via aerosol in the proximity to livestock. These conceivable hazard factors are of specifi c worry for some developing countries where pasteurization is limited and where individuals are living close to their animals [34,40].

Risk factors
In conventional domesticated animals raising system, the different species of animals are often herded together and watering points are common. Such livestock husbandry and management systems can be an important risk factor for animal-to-animal, animal-to human, human-to-animal, and human-to-human M. bovis transmission [82,76].
All species of animals including human beings, body conditions, sex and age groups are susceptible to tuberculosis causing agent [33]. The prevalence of TB in camels were relatively higher in the younger and older camels than other age groups. Different authors have likewise announced in dairy cattle especially that more seasoned animals are infl uenced by TB [83], which could be due to the fact that older animals have weaker immune system. The higher recurrence of lesion in younger camels could be due to the less developed immunity [84]. The [32] likewise report of high prevalence in old camels.
Young camels can also be easily infected with higher doses of Mycobacteria via colostrum's from infected camel in a similar way, as it occurs in cattle [85]. With the goal that the age is one of the most risk factor in camel tuberculosis.
In addition, the pathogen act as risk factor for tuberculosis in camels and other animals. The causative organism is moderately resistant to heat, desiccation and many disinfectants; the virulence of M. bovis relates to its ability to survive and multiply in host macrophages [86].
In Ethiopian transmission of tuberculosis from diseased animal to man is the conduct of preference of raw milk (as compared to pasteurized milk) consumption. The zoonotic risk of tuberculosis frequently connected with utilization (ingestion) of unpasteurized milk and other dairy items infected with M. bovis. Additionally, airborne transmission from cows to-human (or the other way around) ought to be considered as a potential risk factor [87].
The other risk factor is absence of awareness of Zoonotic diseases in the pastoral areas of Ethiopia. The pastoralists demonstrated low familiarity with milk-borne infections. Then again, the members frequently underlined the healthful and restorative benefi t of devouring milk. From pastoralist areas, the Borana people group accept that milk in the udder has no damage and if people don't make it terrible, milk can't be awful "Healthy animal" is "healthy" and most contamination and subsequent lowering of the quality of milk happens after milking. The other thought from Borana pastoralist is, at times, it was likewise noticed that udder wellbeing is a contributing variable for low quality of milk. The milk has 'sickness', when the udder is diseased and they said, "We want raw milk, Boiled milk is dead". Raw milk is good. Only educated people boil milk [88].

Pathogenesis
The animals presented to causative agents of tuberculosis and phosphatidyl inositol mannoside have been shown to intercalate within endosomal membranes and contribute to the arrest in phagosome maturation [90]. In addition, mycobacterial proteins of the antigen complex have been shown to localize within cytoplasmic vacuoles free of mycobacteria [91]. By this mechanism, mycobacteria survive and multiply within the phagosomes and eventually destroy the phagocytes.

Clinical fi nding
Clinical signs in infected camelids tend to be vague or non-existent. Observant owners may detect subtle changes in behaviour. In some, there is a short period of illness terminating with respiratory symptoms. Other signs such as weight loss, loss of appetite, exercise intolerance or an intermittent dry cough are not consistent. Some camelids remain in good body condition until sudden death. As there is no routine surveillance for camelids, it is for the owner or their veterinary surgeon to arrange a post-mortem examination for any dead or moribund animals. The respiratory system and associated lymph nodes are most frequently affected. The lung lesions may be so extensive that it is surprising that severe pathology did not prove fatal earlier. The lesions are white or creamy and caseous. There may be miliary lesions or multiple foci in the lungs, and in more advanced cases, these lesions coalesce to give large areas of caseous necrosis, often involving whole lobes. The lymph nodes of healthy camelids can be small and diffi cult to fi nd. By contrast, tuberculous lymph nodes are often massively enlarged and contain multiple white, cream or yellow-tinged caseous foci and in severe cases, the whole node may be replaced by one large caseous lesion [2].
The respiratory system and associated lymph nodes are most frequently affected. The lung lesions may be so extensive that it is surprising that the severe pathology did not prove fatal earlier [95]. The lesions are white or creamy and caseous.

Pathology
In Ethiopia determination of camel tuberculosis relying  For pathological Lesion In the detail abattoir inspection, lymph nodes including parotid, mandibular, retropharyngeal, tracheobronchial, mediastinal, prescapular, prefemoral, mesenteric, superfi cial inguinal and supramammary lymph node from each camel were examined thoroughly and were incised for the presence of tuberculous lesions. In addition, organs such as lungs, liver, mammary gland and kidneys were also inspected [31,37,34].

Diagnosis of tuberculosis
The Diagnosis of tuberculosis disease in animals is embraced into two stages. The fi rs one is antemortem and the second is post-mortem examination. At ante mortem diagnosis different types of diagnosis can be undertake, such as The single intradermal comparative tuberculin skin test, using tuberculin purifi ed protein derivatives (PPD) extracted from M. bovis (PPDB) and M. avium (PPDA), remains the primary offi cial TB test for camelids [97].
The camelid Interferon-gamma (IFNγ) test detects MTBC and is not M. bovis-specifi c. The results showed that the IFNγ assay, as a test for M. bovis per se, had a low specifi city of between 80% and 98%, with the highest (most desirable) specifi city (98%) giving a disappointingly low sensitivity (~35%) and the highest sensitivity (80%) giving the lowest specifi city. The other is evaluation of gamma interferon and antibody tuberculosis tests in alpacas [98].
The serological tests did not appear to suffer from the low specifi city seen in the IFNγ test. Two of the tests, having a quantitative read-out (IDEXX ELISA and DPP rapid antibody test), were amenable to ROC analysis to set appropriate cutoffs for the data, while both the STAT-PAK rapid antibody test and the ENFERplex multispot ELISA provided qualitative positive/negative readouts not amen-able to ROC analysis.
Infected animals can be detected before onset of clinical signs [43]. The other method of diagnosis of camel TB is clinical signs, necropsy fi ndings and specifi c immune response. In camelids, this strategy is diffi cult to conduct because of the lack of adequate tests for live animals [97]. Tissues specimens are taken from the inspected tubercles and fi xed in 10% neutral formalin [99,[100][101][102].
From Different techniques of diagnosis of camel tuberculosis, the methods which are used by different researchers in Ethiopia are Mycobacterial genus typing(PCR), Post mortem inspection and pathology scoring, Mycobacterial isolation from tissue lesions, Spoligotyping, single intradermal comparative cervical tuberculin (SICCT) test, Ziehl-Neelsen (Z-N) staining and Mycobacteriological culture are the most diagnostic techniques used [31,33,34,37,36].

Distribution of camel tuberculosis in Ethiopia
Ethiopia has high frequency rate of TB infection and the diseases is one of signifi cant general medical issues in the country. The country is one among the universes 22 countries with high TB trouble [103]. Ethiopia, pastoralist territories are notable for high TB prevalence where the pastoralists keep huge number of animals as a method for occupation and endurance technique in the arid and semi-arid regions of the country [2].
Even though, the number of researchers who conduct on camel tuberculosis is limited, the origin of camels on which the researches done are from different pastoral areas of Ethiopia. Table 1 shows that the distribution of camel tuberculosis in different pastoral area of Ethiopia.

Control and Prevention of camel tuberculosis
Effective control requires an understanding of epidemiology of infection within the ecological system that can include domestic as well as wild animal species [104]. Condemnation of carcass and organs during meat inspection, culling of infected animals and pasteurization of milk, eff ective disease control strategies.
The test and slaughter policy is the only one assuring of eradicating TB and relies on the slaughter policy of reactors to the tuberculin test. In affected herd, testing every three months is recommended to rid the herd of individuals that can disseminate infection [105].
Routine hygienic measures aimed at cleaning and disinfection of contaminated premises, food and water troughs are useful. Cattles under poor management were more likely to develop tuberculosis than cattle under good management system [105,106]. Feed troughs should be cleaned and thoroughly disinfected with hot 5% phenol or equivalent cresol as phenols (2-5%), hypochlorites (1-5%), alcohol (usually 70% ethanol), formaldehydes and iodophores (3-5%), and glutaraldehyde [107]. in the occurrence and transmission of zoonotic disease, which is naturally transmitted between vertebrate animal and man. Zoonotic tuberculosis is an infectious disease of domestic animals that can be transmitted from animal to human through consumption of raw milk and meat from infected animals and directly through erogenous route. These possible risk factors are of particular concern for many developing countries where pasteurization is limited and where people are living close to their [34,108].
Ethiopia ranks seventh among the world's 22 countries with high tuberculosis (TB) disease burden and had an estimated incidence rate of 379 cases per 100,000 people per year. TB caused by M. bovis is clinically indistinguishable from TB caused by M. tuberculosis and can only be differentiated by laboratory methods [109].
Tuberculosis as a zoonosis plays an important role among nomadic people where milk and milk products are consumed in raw state. This is true for camel milk. Aerosol transmission may also occur as professional hazard in agriculture and workers as well as to butchers man, which may develop typical pulmonary tuberculosis. The incidence of pulmonary tuberculosis caused by M. bovis in man is signifi cant in occupational groups in contact with infected animals or their carcass particularly in countries where animals kept in barns. The close contact between the owners and their animal could facilitate the transmission of the disease to man [110].
In general, camel tuberculosis similar to bovine tuberculosis results a serious zoonotic impact especially in nomadic population where consumption of raw camel milk and animal products remain the common practice. Based on gross pathology, prevalence's of 5-10% were reported in camels' slaughtered [33]. The risk of being infected through aerogenous route is assumed to be high as there is a close association with camels since the livelihood of the over whelming nomadic population depend on camel especially in countries like Ethiopia. The poor, especially in developing countries, are thought to be at highest risk to contract zoonotic tuberculosis [111] and the observed higher susceptibility of HIV-infected persons to M. bovis infections is of major concern [112].

Conclusions and Recommendations
In Ethiopia, the prevalence recorded on camel tuberculosis and public Health importance or zoonotic importance is rare when we compare to bovine tuberculosis and the economic impacts of camel Tuberculosis was not studied yet.
Studies, which have been conducted in different pastoral areas of the Ethiopia, indicated that the disease has signifi cant effect both in animals and in humans as the result of consumption of uncooked products of camel such as milk and meat.
Pastoral people who was closely tied with rearing of camels are at risk of being infected with zoonotic disease such as camel

Author's contributions
The author read and approved the fi nal manuscript.

Acknowledgement
First I would like praise God, the almighty, the author of