CC BY
02017, Scienceline Publication
World'8 Veterinary Journal
World Vet J, 7(3): 101-107, September 25, 2017
DOI: http://dx.doi.org/10.5455/wvj.20170899
An Abattoir based Study on Bovine Tuberculosis in Debre Zeit, Ethiopia
Mahendra Pal1*, Nigus Zenebe1, Tsedale Amare1 and Tefera Woldemariam1'2
1Department of Microbiology, Immunology and Public Health, College of Veterinary Medicine and Agriculture, Addis Ababa University, P.B.No.34, DebreZeit, Ethiopia 2College of Veterinary Medicine, Hawassa University, Ethiopia "Corresponding author's Email: palmahendra2@gmail.com
ABSTRACT
Members of the Mycobacterium complex group cause tuberculosis, it recognized as one of the most important threats to humans and animals causing mortality, morbidity and economic losses in many countries of the world, particularly in developing nations. Therefore, a cross-sectional study on bovine tuberculosis conducted in order to determine its prevalence in cattle at the ELFORA export abattoir in Debre-Zeit in the period from November 2014 to April 2015. Routine and detailed meat inspection methods used to detect lesions. Three hundred cattle inspected; their body condition scores and ages recorded before slaughtering. Of the total animals, 5.7% (17/300) had lesions of tuberculosis. Out of these, routine abattoir inspection had detected only 2.7% (8/300) with visible lesions and there was poor agreement (kappa=0.09) between routine and detailed inspection methods. The proportion of lesions fou d in the lung and associated lymph nodes, mesenteric lymph nodes and lymph node around head were determined to have been at 12.3%, 2% and 3.3%, respectively. The prevalence of the disease was significantly (P < 0.05) varying with body condition scores but it did not significantly (P > 0.05) vary with age groups of the animals. This study demonstrated the prevalence of bovine tuberculosis in cattle slaughtered at ELFORA export abattoir and low sensitivity of routine abattoir inspection. Hence, the carcass must thoroughly examine well to reduce the chance of missing lesions of tuberculosis.
Key words: Bovine tuberculosis, Meat inspection, Prevalence, Public health, Zoonosis INTRODUCTION
Bovine Tuberculosis (BTB) is a chronic bacterial disease characterized by progressive development of tubercles in any tissue/organ of the body (Hlokwe et al., 2013; Pal et al., 2014; Terefe, 2014). It has recognized from 176 countries as one of the important bovine diseases causing great economic loss (Awah-Ndukum et al., 2013). Tuberculosis (TB) remains a major global health problem and causes ill health among millions of people each year and ranks as the second leading cause of death from an infectious disease worldwide after the human immunodeficiency virus (HIV) (WHO, 2013 and 2014). Tuberculosis can be difficult to diagnose based only on the clinical signs. Regular surveillance by skin test, bacteriology and molecular methods is not feasible due to lack of resources. Thus, Routine Abattoir (RA) inspection will continue to play a key role for national surveillance. We evaluated the efficiency of RA inspection for diagnosis of M. bovis infection and discussed its public health implications in light of a high risk of human exposure. TB has been widely distributed throughout the world affecting all age groups. In humans, TB is being responsible for more deaths than any other bacterial disease ever today (Bhatia and Ichpujanti, 1994). Ethiopia has the largest livestock population in Africa, with an estimated 44.3 million cattle, 23.6 million sheep, 26.3 million goats and 2.3 million camels (CSA, 2005). Ethiopia's increasing human population, coupled with expanding urbanization and higher average income is putting an increasing pressure on the meat supply. To meet this demand, millions of food animals slaughtered every year
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throughout the country. In 2007, for example, a total of 18.8 million cattle, sheep, goats and camels slaughtered at municipal abattoirs, primarily for domestic consumption (FAO, 2009). For this reason, close monitoring of meat hygiene, including proper implementation of meat inspection procedures during slaughter, should be a vital part of the national public health protection program.
BTB characterized by the formation of nodules called tubercles whose location depends largely on the route of infection. In calves, BTB usually transmitted by ingestion and lesions involve the mesenteric lymph nodes with possible spread to other organs. In older cattle, infection usually transmitted by the respiratory tract with lesions in the lung and dependent lymph nodes (Carter and Wise, 2004). Recently, there have been increasing reports of human cases due to M. bovis especially in patients with HIV (Russell, 2003). Thus, a greater degree of transmission of infection with bacteria to human and domestic farm animals could occur (Taracha et al., 2003). In industrialized countries, animal tuberculosis is controlled and eliminated with milk pasteurization, which has in turn drastically reduced the incidence of the disease caused by M. bovis in both cattle and human. In developing countries however, animals' tuberculosis is widely distributed, control measures not applied or applied sporadically and pasteurization rarely practiced. In Ethiopia, animals are kept in the same dwelling with their owners and use of cow dung for wall plaster, floor and as a source of energy for cooking, do exacerbate chance of spread of tuberculosis to human (Asseged, 1999). Thus, BTB is endemic and has reported from different regions of the country (Asseged et al., 2000). The disease in the country is associated with decreased productive efficiency and carcass or organ condemnation in abattoir (Shitaye et al., 2006). The nationwide distribution of the disease and the economic loss associated with it has not been fully determined due to lack of good diagnostic facilities (Asseged, 2004). The primary reason for post mortem examination of carcasses at slaughterhouse is for the protection of public health. TB status of slaughter cattle provides useful information and is a proxy indicator for the prevalence of TB-positive slaughter animals, and therefore likelihood of the human exposure through consumption of infected meat. Apart from providing data for regulatory programmatic awareness of the true prevalence of TB infection, carcass examination also provides clues as to whether the infection is in its early stage or has reached the transmissible stage (ADARDO, 2008). This provides better programmatic awareness with subsequent development of targeted guidance on how to reduce the risk of TB spread within the specific geographic area, as well as opportunities to trace back the source of infection to the herds. Hence, having the knowledge of distribution, prevalence and risk factors of the disease are fundamental to look for effective control strategy. Therefore, the objectives of this study were to determine the prevalence of bovine tuberculosis at the ELFORA export abattoir, in DebreZeit and to evaluate the efficiency of abattoir inspection for the diagnosis of M. bovis infection as well as to assess the distribution of tuberculous lesions in slaughtered animals.
MATERIALS AND METHODS
Ethical considerations
This research work conducted according to Organization International Epizootics (OIE, 2010) principles of the use of animals in research and education. As much as possible we prevent, alleviate and minimize pain, suffering, and distress and enhance welfare for the animals used for research during ant mortem.
Study area
This study conducted at the ELFORA export abattoir in DebreZeit, Ethiopia from November 2014 to April 2015. DebreZeit is located at 45 kms southeast of Addis Ababa. The area is located at 9°N latitude and 40°E longitudes at an altitude of 1850 meters above sea level in central high land of Ethiopia. It has an annual rainfall of 866 mm of which 84% is in the long rainy season (June to September). The dry season extends from October to February. The mean annual maximum and minimum temperatures are 26°C and 14°C, respectively, with mean relatively, humidity of 61.3% (ADARDO, 2007).
Animals
Animals used for the study were those, which were ready to slaughter at ELFORA export abattoir, in DebreZiet, came from surrounding areas and all of them were from local breeds (Boss indicus) and male. Most of the cattle kept in fattening for variable period, so their body condition was almost medium or good (Nicholson and Butterworth, 1986).
Study design
A cross-sectional study conducted to determine the prevalence of BTB. The efficiency of routine abattoir meat inspection to diagnose TB lesions also evaluated. A systematic random sampling procedure used to choose animals in the study. In general, 300 cattle and their carcasses examined.
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Ante-mortem inspection
Those cattle selected for the study had been examined physically before slaughtering; age and Body Condition Score (BCS) recorded. The body condition of each of the study animals scored using guideline established by Nicholson and Butterworth (1986) during ante-mortem examination. In the meantime, the age of the study animals had also been determined according to De-Lahunta, and Habel (1986). The age was categorized as young less than two years old, young adult between two to six years old and adult greater than six years old (Pace and Wakeman, 2003). All animals slaughtered during the study period were older than two years of age so they categorized as young adult and adult.
Routine abattoir inspection
Routine inspection for tuberculosis at the abattoir conducted according to the method developed by the meat inspector and quarantine division of the Ministry of Agriculture, Ethiopia (MOA, 1973). The method involves palpation and incision of the bronchial, mediastinal and pre-scapular lymph nodes, as well as visual inspection and if necessary incision of the lungs, liver, kidneys and lymph nodes around these organs.
Detailed post-mortem examination
Detailed post-mortem examination performed in such a way, that the lungs and lymph nodes removed for the investigation of tuberculous lesions. The seven lobes of the two lungs, including the left apical, left cardiac, left diaphragmatic, right apical, right cardiac, right diaphragmatic and right accessory lobes, inspected externally and palpated. Each lobe then sectioned into about two centimeter thick slices to facilitate the detection of lesions. Similarly, lymph nodes, namely, the mandibular, medial right apical, right cardiac, right diaphragmatic and right accessory lobes, were inspected externally and palpated, each lobe was then sectioned into about two centimeter thick slices to facilitate the detection of lesions. Similarly, lymph nodes, namely, the mandibular, medial retropharyngeal, cranial and caudal mediastinal, left and right bronchial, hepatic and mesenteric lymph nodes, were sliced into thin sections (23 millimeter thick) and inspected for the presence of lesions (Teklu et al.,2004).
Data analysis
The raw data was fed into Microsoft excel and the prevalence of bovine tuberculosis was calculated in percentage. The variation between different factors assessed by using Chi-square (X2), and all statistical analyses conducted by SPSS statistical software version 20. A p-value less than 0.05 considered statistically significant.
RESULTS
Prevalence of bovine tuberculosis
The overall prevalence of BTB in cattle slaughtered at ELFORA export abattoir during the study period was at 5.7% (17/300) based on the detailed post-mortem examination. Macroscopically, the most common changes seen in the affected organs and/or lymph nodes were the presence of circumscribed yellowish white lesions of various sizes and numbers. However, only 2.7% (8/300) head of cattle found to have detectable tuberculosis lesions by the routine abattoir inspection. Thus, the proportion of lesion detected by detailed examination to that of routine abattoir inspection procedure was in the ratio of 2.1:1. The results of this study have indicated that the probability of missing an animal with tuberculosis during routine abattoir inspection was 3%.
Thus, a poor agreement (Kappa=0.09) was recorded between these two procedures. Distribution of tuberculosis lesions in organs of cattle slaughtered is higher in bronchial ln (3%) and lower in hepatic ln (Table 1). The lymph node and lung regions contribute a higher percentage of tubercle lesions than any other organs (Table 2). The prevalence of tuberculosis in abattoir slaughter cattle in relation with age and body condition score has been presented in table 3. There was no statistically significant (P> 0.05) difference between age groups. However, there was a variation in the occurrence of tuberculous lesions across body condition scores (medium and good), with a considerably higher prevalence recorded in medium scored cattle.
Distribution of tuberculous lesions
The distribution of tuberculous lesions in different tissues of cattle has presented in table 1. Eight organs and/or lymph nodes were containing tuberculous lesions. About 5.3% of the lesions observed in the lung. The lung region contributes a higher percentage of tubercle lesions than the lymph node around head and the gastrointestinal area (Table 2). The prevalence of tuberculosis in abattoir slaughter cattle in relation with age and BCS presented in Table 3 and 4, respectively. There was no statistically significant (P> 0.05) difference between age groups. However, there was a
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variation in the occurrence of tuberculous lesions across body condition scores (medium and good), with a considerably higher prevalence recorded in medium scored cattle.
Table 1. Distribution of tuberculosis lesions in organs of cattle slaughtered in central Ethiopia, during November 2014 to April 2015
Liver And Hepatic
Organs Lung Tissue Bronchial Mediastinal Retropharyngeal Mandibular Mesenteric Carcasses
No. of lesions (%) 16 (5.3) 8 (3) 14(5) 7(2.3) 3 (1) 6 (2) 2 (0.7) 5 (1.6)
*ln= lymph node
Table 2. Observation of tuberculosis lesions distributed in organs and lymph nodes of cattle carcasses collected in the central Ethiopia, during November 2014 to April 2015
lung tissues and lymph node Mesenteric ly mph node Liver and hepatic lymph node Head lymph nodes
Anatomical sites Carcasses Total
No. of Lesions 37 6 1 10 5 59
Infected animal (%)* 12.3 2 0.3 3.3 1.7 --
Percentage of infected organ (%)** 62.7 10.2 1.7 17 8.5 --
*Percentage from total animal=lesion divided by/number of animal examined (300) multiplied by 100 **Organ proportion=lesion in the region divided by overall lesions (59) multiplied by 100
Table 3. Prevalence of bovine tuberculosis with respect to age of infected animals
Age Young Adult Total
No. of Animals examined 123 Positive (%) 9 (7.3) P-value 0.99 177 11 (6.2) 0.99 300
Table 4. Prevalence of bovine tuberculosis with respect to body condition score of infected animals
Body condition score Good No. of Animals examined 237 Positive (%) 5 (2.1) P-value 0.00 Medium 63 14 (22.2) 0.00 Total 300
Figure 1. Tuberculosis lesions in the thoracic cavity of adult cattle at abattoir, in central Ethiopia, September 2015
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DISCUSSION
This study has documented the prevalence and distribution of lesions of BTB in cattle slaughtered at ELFORA export abattoir. The findings of overall prevalence of 5.7% tuberculosis reported in detailed post-mortem examination and 2.7% in routine abattoir inspection are in agreement with the results reported by Demelash et al. (2009; Teklu et al., 2004; Nasaka J, 2014) in Yabello municipal abattoir and Hosanna Ethiopia and Masaka district Uganda 4.2% 4.5% and2.7%respectively.
On the contrary, the present results are less than of the previous reports from Ghana 34% (Atiadeve et al., 2014), Camerron 12-17% (Egbe et al., 2016), Ethiopia 8.4% (Aylate et al., 2013), Butajira municipality abattoir 11.50% (Abdurrahman, 2009), Addis Ababa and Adama 10.10% (Demelash et al., 2009), Adama municipal abattoir 24.70% (Tefera, 2009) and 19.8% record from cattle slaughter in rural Tanzania (Cleaveland et al., 2007). This could indicate the endemic nature of the disease and the high infection rate prevailing in the general population of slaughter cattle in Ethiopia. This study has revealed that the probability of missing an animal with TB lesion during routine abattoirinspection is 95.24%. Previous studies have also indicated probabilities of 84.85% (Tefera, 2009), 84% (Corner, 1994.) and 70.59%, (Teklu et al., 2004). Therefore, detailed post-mortem examination can considered as a better procedure to detect tuberculous lesion. This study had also revealed a much low sensitivity of routine meat inspection to detect carcasses with tuberculous lesion, implying that large proportion (95.24%) of tuberculosis infected carcasses pass undetected and the meat is approved for human consumption. The most probable explanation for the failure of standard meat inspection correctly detect tuberculosis infection could be due to the manner of examination (Corner, 1994). It noticed that in standard meat inspection procedure only few sites (organs) often inspected at a glance due to heavy duty of inspecting large number of animals each day. Argued that in abattoir smaller lesion could missed due to limited time available for the examination of each tissue (Corner, 1994). Furthermore, a lack of competence in meat inspection training could be another reason for inefficiency of the service as most of the lack of adequate trained personnel in the area of meat inspection. In the present study, gross tuberculosis lesions were found most frequently in the lymph nodes of lung (12.3%), lymph nodes of the head (3.3%) followed by mesenteric lymph node (2%). This finding is consistent with previous studies done by (Firdissa 2006; Abdurrahman, 2009 and Tefera, 2009) that reported 11.7, 14 and 14.7% TB lesions in lungs and associated lymph nodes, respectively. However, Corner (1994) described that up to 95% of cattle with visible TB lesions could identified by the examination of the lungs and associated lymph nodes. This finding indicated that inhalation might be the principal route of TB infection in cattle. Therefore, during post-mortem examination, focus should give on lungs and its associated lymph nodes. The presence of lesions in mesenteric lymph nodes indicated that the infection occurs through ingestion (Radostits et al., 2007). The prevalence of the diseases was statistically insignificant in age categories, which agree with previous reports (Bekele and Belay, 2011). This might be due to type of animals slaughtered in the abattoir in which both were greater than two years of age, which is enough to develop the lesions once infected. It should noticed that, there was a statistically significant difference (P< 0.05) in the prevalence of the disease between BCS. The prevalence was higher in medium (22.2%) than good (2.1%) body conditioned animals. Our findings run parallel with previous reports, which had indicated that animals with good BCS have relatively strong immunological response to the infectious agent than animals with medium BCS and the results could indicate the wasting nature of the disease (Radostits et al., 2007). Our current work is a continuation of the work published earlier describing prevalence of BTB in Ethiopian slaughter cattle (Demelash et al., 2009). With generation of new additional data from laboratory work (culture and microscopy and molecular analysis), we wanted to evaluate how well abattoir meat inspection protocols in Ethiopia are performing to detect cattle infected with M. bovis. Public health implications of the findings have also discussed.
CONCLUSION
This study demonstrated the limited capacity of current meat inspection procedures in Ethiopia to detect carcasses infected with M. bovis.in Ethiopia and other countries where dietary preferences mean that a significant proportion of meat customarily consumed raw, lack of effective slaughter inspection protocols represents significant risk. Thus, meat borne zoonotic TB continues to be an ongoing and an important threat to public health in a nation that has significant populations of vulnerable HIV-infected citizens. Therefore, it is necessary to understand that the detailed abattoir meat inspection prevails than routine meat inspection, giving safe meat consumption risk and minimize the other risk factors. It deduced that BTB is prevalent in cattle slaughtered at ELFORA export abattoir, Debre-Zeit, Ethiopia. Tuberculous lesions were detected using detailed meat inspection. This should practice giving more attention to the lungs and associated lymph nodes.
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Recommendations for improving the service within the context of the prevailing cultural and socio-economic situation generated as an important outcome of these efforts. Further studies needed to characterize the organism by cultural isolation and implementing molecular techniques.
Acknowledgements
This work done by the generous financial support from Department of Microbiology, Immunology and Public Health, College of Veterinary Medicine and Agriculture, Addis Ababa University. The authors are grateful to the General Manager of abattoir AtoKibret Haile for facilitating the research work at the abattoir. We also would like to appreciate all participants who contributed during sample collection.
Competing interests
The authors have declared that no competing interest exists in relation to this manuscript. Author's contribution
NigusZenebe designed the experiment, collected data, Tsedale Amare collected data, TeferaWoldemariam helped in manuscript writing, commenting and approval, Mahendra Pal designed the experiment, wrote, commenting and approval of the paper. All authors have read and approved the final manuscript.
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