Epidemiology and Public Health Implication of Bovine Tuberculosis in and Around Mekelle, Northern Ethiopia
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Date
2011-06-01
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Addis Ababa University
Abstract
Bovine tuberculosis (BTB), caused by Mycobacterium bovis, is a well-known zoonotic and
economically important disease which affects cattle world-wide. A cross-sectional study was
conducted on 1248 cattle and 120 cattle owners in Mekelle City and its surroundings from
September 2010 to May 2011 to assess the epidemiology and public health implication of BTB
using comparative interadermal tuberculin test (CIDT), postmortem and bacteriological
examinations, molecular typing and questionnaire. Accordingly, 120 herds comprising 480 cattle
were subjected to CIDT, and the herd and individual animal prevalence were 20% (24/120) and
11 .25% (54/480), respectively. The herd level prevalence varied significantly among different
type of farming (x2=4 .37; P=0.036), herd size (x2=19.47; P<0.001) and management (x2=25.04 ;
P<0.001). Cattle herd in intensive type of production (OR=3.67) and under poor management
conditions (OR=4.28) had a higher odds for tuberculin reactivity compared to those cattle herd
managed under extensive production type and good management conditions, respectively. Cattle
kept in herds which had >10 cattle (OR=13.53) and cattle kept under intensive farming system
(OR=4.79) had a higher odds for tuberculin reactivity compared to those cattle kept with herds
had less than five cattle and cattle managed under extensive type of production, respectively. of
the animal characteristics, sex (x2=8.1; P=0.004), breed (x2=15.03 ; P=0.001) and body condition
(x2=6 .65; P=0.036) were significantly associated with the prevalence of BTB. Female
(OR=4.81), poor body condition (OR=2.65), exotic (OR=6.13) and cross (OR=6.61) had a higher
odds for tuberculin reactivity compared to male, good body condition, and Zebu, respectively. of
the 54 CIDT positive cows, four were slaughtered and TB lesion was detected in all the four
cattle and 57 % of the lesions were found in the thoracic cavity. In addition, of the total 768 cattle
subjected to postmortem examination, 49 (6.39%) were found to be positive for gross tuberculous
lesions. Larger proportion (62.3%) of TB lesion was recorded in thoracic cavity followed by
retropharyngeal lymph nodes (22.95%). Culture positivity in primary culture media was
confirmed in 44.2% (27/61) in tissue sample and 12.9% (4/31) in milk sample. Mycobacterium
genus typing of the 29 culture isolates using multiplex PCR analysis indicated that only four
isolates positive for the genus Mycobacterium of which two were members of the Mycobacterium
tuberculosis complex. Awareness of cattle owners about BTB was generally poor and thus cattle
owners were found to consume raw milk, soured milk product (yoghurt) and shared the same
shelter with their cattle. A total of 1272 TB patients received short course therapy in Mekelle
hospital within live years, of which 62.03% (789/1 ,272) were pulmonary TB and 37.97%
(483/1 ,272) were extra-pulmonary TB patients. In conclusion, this study revealed the importance
of BTB in the study area in particular and the region in general. Thus, detection of BTB both in
live and slaughtered animals, lower awareness of cattle owners about the disease and the
prevailing habit of consumption of animal products and isolation of M. tuberculosis complex
from animal tissue and milk would suggest the potential role of BTB as a zoonosis. Therefore,
practical and sound control methods such as strict meat inspection, boiling of milk and cooking
of meat, and public education to raise the awareness on the transmission of the disease are
recommended
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Keywords
Bovine tuberculosis, Cattle, CIDT test, Epidemiology, Mekelle, M. tuberculosis complex, Postmortem examination, Public Health