The Prevalence of Bovine Tuberculosis

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Published on International Journal of Agriculture & Agribusiness
Publication Date: May 1, 2019

Kindalem Bayew Wassie
Animal Health Department Head in Janamora Wereda Livestock Development Office
Janamora, Ethiopia

Journal Full Text PDF: The Prevalence of Bovine Tuberculosis (Study in Gondar Municipal Abattoir).

Abstract
A study was conducted from October, 2017 to February, 2018 to determine the prevalence of bovine tuberculosis in Gondar municipal abattoir with the objective of to determine the prevalence of bovine tuberculosis at Gondar municipal abattoir, to asses’ risk factors which increase the susceptibility of cattle to tuberculosis, to assess the distribution of tuberculous lesion in slaughter animal, and to evaluate the efficiency of abattoir inspection for the diagnosis of M. bovis infection. A total of 412 cattle were examined in the abattoir. As the table 5 shows that prevalence of Bovine tuberculosis with respect to young and adult is 19.8% (28/141) and 18.7% (31/271) respectively. Prevalence of bovine tuberculosis with respect to body condition score of fat and medium body animal is 4.9% (15/301) and 39.6% (44/111) respectively. The overall prevalence of Bovine tuberculosis in cattle slaughtered in Gondar municipality abattoir during the study period was 14.3% (59/412) based on 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 1.7% (7/412) head of cattle were found to have detectable Tuberculosis lesion by the routine abattoir inspection in (Table 1). The prevalence of organ proportion with respect to Pooled lesion distribution is lymph nodes around Head, lung and lymph nodes around it, mesenteric lymph node and liver and hepatic lymph nodes are 26.4%, 54.7%, 13.2% and 5.7% respectively. Lung and lymph nodes around it is the highest (54.7%) and liver and hepatic lymph node is the lowest (5.7%) prevalence when compared to other organs.

Keywords: Gondar, Abattoir, Bovine tuberculosis, Cattle & Meat inspection.

1. INTRODUCTION
The livestock population in Ethiopia is estimated to be 41.5 million cattle, 14.6 million sheep, 13.6 million goat, 5.8 million equines, 1.7 million camels and 42.9 million poultry [1]. However, thus huge resource Ethiopian livestock productivity is lower than the African average; this low level of livestock productivity is also reflected in the very low per capital consumption of animal protein which is estimated at 20 – 23 kg. This figure is only 10% of per capital consumption of similar products in the developed world. The major biological constraints contributing to low productivity include low genetic potential of the animal, poor nutrition and prevalence disease like brucellosis and tuberculosis [2].
Tuberculosis (TB) is an infectious disease caused by Mycobacteria that has been a major health risk to man and animals for more than a century. It is widely distributed throughout the world affecting all age groups of humans and animals. In humans, it is being responsible for more deaths than any other bacterial disease ever today [3].
Developing countries have nearly two-third of the world livestock population, but produce less than a third of world’s meat and a fifth of its milk requirement [4]. To feed their people developing countries need to intensity their livestock population system. However, intensification has been hindered by diseases such as tuberculosis, mastitis and respiratory disease. Bovine tuberculosis (BTB) is one of the important diseases of intensification not only to its effect on animal production but also due to its public health significance [5]. The world health organization (WHO) estimates human tuberculosis (HTB) incident and death for 1990-1999 to be 88 million and 30 million reservedly, with most case in developing countries [6].
In a developing countries including Ethiopian where M.bovis infection is presented in a number of animal species. Having the knowledge of distribution, prevalence, risk factors and zoonotic implication of the disease is a fundamental so as to look for effective control strategy. It‘s major economic impact in developing countries like Ethiopia is associated with decreased productive efficiency and carcass, organ condemnation in abattoir [7]. Approximately 85% of the cattle and 82% of human population of Africa are in areas where BTB is either partial controlled or not control at all [8]. In Africa, of the 55 nations, 25 reported sporadic occurrence of bovine TB, 6 reported enzootic disease, 2 (Malawi and Mali) were described as having a high occurrence, 4 did not report the disease and the remaining 18 countries did not have data. Of all nations in Africa, only 7 apply disease control measures as part of a test and slaughter policy and considered BTB as notifiable disease; the remaining 48 control the disease inadequately or not at all. Almost 15% of the cattle population is found in countries where Bovine TB is not notifiable and test and slaughter policy used. Thus approximately 85% of the cattle and 82% of the human population of Africa are in areas where BTB is either partly controlled or not at all [6].
In developing countries however, animal TB is widely distribution, control measures are not applied or are applied sporadically and pasteurization is rarely practiced. The direct correlation between M.bovis infection in cattle and disease in human population has been well documented in industrialized countries. Whereas little information is available from developing countries [6].
Bovine tuberculosis has major economic impact, associated with reduction of productive efficiency and carcass/organ condemnations in abattoir mostly in developing countries [7]. In Ethiopia, BTB is considered as prevalent disease in animal population; however there is limited information on tuberculosis status in different region of countries [9]. Therefore, the objectives of this study were:
a. To determine the prevalence of bovine tuberculosis at Gondar municipal abattoir.
b. To asses risk factors which increase the susceptibility of cattle to tuberculosis.
c. To assess the distribution of tuberculous lesion in slaughter animal.
d. To evaluate the efficiency of abattoir inspection for the diagnosis of M. bovis infection.

2. MATERIALS AND METHODS
2.1. Study Area
The study was conducted from October 2018 to March, 2019 at Gondar municipal abattoir. Gondar is a city which is located in the Semien Gondar zone of the Amhara Region. It is north of Lake Tana on the lesser Angereb River and south west of the Semien Mountains. It has a latitude and longitude of 12o36’N 37o28’E/ 12.600oN 37.467 o E with an elevation of 2133 meters above sea level. Gondar served as a strong Christian kingdom for many years. Fasil Castle and Debre Birhan Selassie church are the UNESCO recorded historical place found in Gondar [10].

2.2. Study Animals
The study animals are cattle. Those animals which are ready to be slaughter of in Gondar municipal abattoir came from Gondar zuria, Wereta, Amba Giorgis, Tkl Dngay and Gondar town. All cattle that come from those areas were local breed and male.

2.3. The Study Design
A cross-sectional study was conducted to determine the prevalence of Bovine tuberculosis. The efficiency of routine abattoir meat inspection to diagnose Tuberculosis lesions was also evaluated. A systematic random sampling procedure was used to include animals in the study. In general, 412 cattle and their carcasses were examined.

2.4. Ante-mortem Examination
Those cattle included in the sample size were examined physically before slaughtering; age and body condition score (BCS) of the animals were recorded.

2.4.1 Body Condition Scoring and Age Determination
The body condition of each of the study animals was scored using guideline established by Nicholson and Butterworth [11] during ante-mortem examination. The study animals were classified as medium and fat. In the mean time, the age of the study animals also were determined according to De-Lahunta and Habel [12].

2.5. Routine Abattoir Inspection
Routine inspection for detection tuberculosis at the abattoir is conducted according to the method developed by the meat inspector and Quarantine division of the Ministry of Agriculture [13]. The method involves palpation and incision of the bronchial, mediastinal and prescapular lymph nodes, as well as visual inspection and incision of the lungs, liver, kidneys, udder and lymph nodes around these organs. The whole carcass is condemned if generalized tubercle with involvement of carcass lymph node is diagnosed. Otherwise, only the infected organ is rejected.

2.6. Detailed Post-mortem Examination
Detailed post-mortem examinations was performed; the lungs and lymph nodes were 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, were inspected externally and palpated, each lobe was then sectioned into about 2-cm-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 (circa 23 mm think) and inspected for the presence of visible lesions. [14].

2.7. Laboratory Examination
The lymph nodes, medial retropharyngeal, trachiobronchial, mediastinal, prescapular, mesenteric and other tissue specimens were cut into slices of 2 mm using sterile surgical blades (cross contamination of the specimens from different animals was avoided by using different surgical blades). Then the cut surfaces were examined for the presence of abscess, cheesy masses and tubercles. Tissues with suspected lesions were subjected to bacteriological examination for confirmation and identification. The sample by used sterile universal bottle add saline kept by ice box Upon arrival to Gondar University Veterinary laboratory, individual tissues were macerated using sterile blades in sterile Petri dishes to obtain fine pieces, then crashed using pestle and mortar rinsing in Phosphate Buffer Saline (PBS) and homogenized for 10 minutes. The homogenate was then decontaminated using 4% NaOH for 15 minutes adding equal volume as the homogenate, centrifuged at 3,000 rpm for another 15 min and neutralized by 1% (0.1N) HCl using phenol red as an indicator. The sediment is then inoculated into a set of Lowenstein Jensen (LJ) media slants supplemented with 0.4% sodium pyruvate (LJ pyruvate) and glycerol (standard LJ). Cultures were incubated aerobically at 37oC for up to 3-8 weeks, with weekly observation for discernible growth [15]. Further characterization was done using identification of the Mycobacterium species based on the rate of growth and colony morphology, species belonging to the M. tuberculosis complex show a slow growth rate. For further identification of the Mycobacteria species, the growth of M. tuberculosis is enhanced by glycerol. Accordingly the mycobacteriums were considered to be M. bovis if the growth is slow and colonies are small in size. If their growth enhanced by pyruvate the probability of the colony to be M. tuberculosis is null. When visible colonies were observed, ZN staining was performed to confirm the presence acid fast bacilli [16].

2.8. Data Collection and Data Management
The individual animal identification number, breeds, sex, age and body condition of the animal were recorded. Body condition scoring was made using a method developed for Zebu cattle [11]. Age category was given by using the dental eruption and wear as described by De Lanta and Habel, [12]. The range and frequency of anatomical sites where tuberculosis lesion were detected were also recorded for affected cattle. The results of routine abattoir inspection, detailed laboratory examination and isolation and identification of mycobacterium were recorded to evaluate the efficiency of routine abattoir inspection procedures to diagnose tuberculous animal.

2.9. Data Analysis
The prevalence of bovine tuberculosis is defined as the number of animals which are tuberculosis lesion positive per the number of animals inspected at post-mortem and was expressed in percentages. The raw data was fed into Microsoft Excel 2007 for analysis and the variation between different factors was assessed by using chi square (x2) and SPSS 20. A p-value of < 0.05 was considered to be statically significant.

3. RESULT
3.1. Prevalence
The overall prevalence of Bovine tuberculosis in cattle slaughtered in Gondar municipality abattoir during the study period was 14.3% (59/412) based on 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 1.7% (7/412) head of cattle were found to have detectable Tuberculosis lesion by the routine abattoir inspection in (Table 1).

3.2. Distribution of Tuberculous Lesion
The distribution of tuberculous lesion in different tissue of the study cattle was presented in table 2. 7 organs and/or lymph nodes were found to contain tuberculous lesion. The lung region contributes a higher percentage of tubercle lesions than the head and the gastro intestinal area (Table 3). The prevalence of organ proportion with respect to Pooled lesion distribution is lymph nodes around Head, lung and lymph nodes around it, mesenteric lymph node and liver and hepatic lymph nodes are 26.4%, 54.7%, 13.2% and 5.7% respectively. Lung and lymph nodes around it is the highest (54.7%) and liver and hepatic lymph node is the lowest (5.7%) prevalence when compared to other organs. The prevalence of tuberculosis in Gondar municipality abattoir slaughter cattle and its association with age and body condition score is presented in Table 5. The results showed that young adult cattle tended to develop lesions at a relatively lower rate than adults. There was also a variation in occurrence of tuberculous lesion across body condition score with considerable higher prevalence recorded in medium cattle. As the table 5 shows that prevalence of Bovine tuberculosis with respect to young and adult is 19.8% (28/141) and 18.7% (31/271) respectively. Prevalence of bovine tuberculosis with respect to body condition score of fat and medium body animal is 4.9% (15/301) and 39.6% (44/111) respectively.

4. DISCUSSION
This study has documented the magnitude and distribution of lesion compatible with Bovine tuberculosis in Gondar slaughter cattle the finding of overall 14.3% prevalence of tuberculosis reported in detail post-mortem examination and 1.7% of routine abattoir inspection. This finding is higher nthan the finding of Ameni and Wudie, [17] reported Bovine tuberculosis in Adama municipal abattoir with the prevalence of 5.2%. In the present study, gross tuberculosis lesions were found most frequently in the lymph nodes of lung and lung (54.7%), lymph nodes of the head (26.4%) followed by mesenteric lymph node (13.2%), and hepatic lymph node (5.7%) . This finding is contrary with previous studies done in Ethiopia by Firdissa [18] Nesredin [19] and Abdurohama [20] where the prevalence of 67.7%, 70% and 70.7% Tuberculosis lesions were reported in lungs and associated lymph nodes, respectively. Therefore, during post mortem examination, focus should be given on lungs and associated lymph nodes. The presence of lesions in mesenteric lymph nodes indicates that the infection occurs through ingestion [7]. The prevalence of the disease within respect body condition score, the prevalence being highest in medium body condition (39.6%) compared to fatty animals (4.9 %). This finding indicates that the wasting nature of the disease. The present result is consistent with previous reports which indicated that animals with good Body Condition Score have relatively good immunological response to the infectious agent than animals with medium Body Condition Score [7]. Based on this conclusion, the following recommendations are forwarded: a. Ante mortem and post mortem examination should occur in an abattoir. b. Inspection of meat should be occurs in as a guidelines. c. Extension should give to the society about bovine tuberculosis. d. Abattoir surveillance should be carried out in every slaughter house across the country to reduce human infection.