EPIDEMIOLOGY OF TUBERCULOSIS AND MOLECULAR CHARACTERIZATION OF MYCOBACTERIUM TUBERCULOSIS COMPLEX SPECIES IN GOATS AND THEIR OWNERS IN ADAMI TULU JIDO KOMBOLCHA DISTRICT, EAST SHEWA ZONE OF OROMIA
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2014-06
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Abstract
Cross-sectional and case-control studies were conducted from November, 2013 to July, 2014 to investigate epidemiology of tuberculosis (TB) and perform molecular characterization of Mycobacterium tuberculosis complex (MBC) species in goats and their owners in Adami Tulu Jido Kombolcha (ATJK) district by comparative intradermal tuberculin (CIDT) test, bacteriological and postmortem examination and molecular characterization techniques. A cross-sectional study was conducted on a total of 97 flocks comprising 527 goats from rural and urban villages by CIDT test and flock prevalence was 15.5% (95% CI: 5.7-19.0) at ≥2mm cut-off points and 12.4% (95% CI: 8.1-22.8) at ≥4mm cut-off points while animal level prevalence was 4.6 % (95% CI: 2.8-6.3) at ≥2mm cut-off points and 3.8% (95% CI: 2.2-5.4) at ≥4mm cut-off points. None of animal characteristics considered were associated with CIDT positivity of goats (P>0.05). A case-control study was conducted on a total of 70 flocks comprising 283 goats by CIDT test and 31.6% of flocks owned by TB positive cases and 15.6% of flocks owned by TB free controls were positive to bovine tuberculin test at ≥2mm cut-off. The overall flock prevalence was 24.3% (95% CI: 14.0-34.6) at ≥2mm and 20% (95% CI: 10.4-29.6) at ≥4mm cut-off points. At both cut-off points the CIDT positive flock proportion was not statistically significant (P>0.05). However, 14.4% of goats owned by TB positive cases and 4.1 % of goats owned by TB free controls were positive to CIDT test. The overall animal level prevalence was 9.9% (95% CI: 6.4-13.4) at ≥2mm a cut-off while it was 8.8% (95% CI: 5.5-12.2) at ≥4mm cut-off. Animal prevalence was statistically significant P=0.004 at both cut-off points. The risk of acquiring caprine TB infection of goats being owned by TB positive cases was 0.40 times higher than being owned by TB free controls at both cut-off points. 38 specimens of human sputum and 7 tuberculous tissue lesions obtained from CIDT test positive goats were cultured and 31.6% human sputum and 14.3% of tuberculous tissue lesions showed growths on Lowenstein-Jensen (LJ) media. Genus typing of goat isolates using multiplex polymerase chain reaction (m-PCR) revealed a product characteristic to genus Mycobacterium. Furthermore, 91.7% of the 12 heat-killed positive human isolates had intact direct repeat (RD) 9 locus up on deletion typing for RD9, and subsequently classified as M. tuberculosis. Both human and goat isolates were spoligotyped and two lineages; Euro-American (E-A) and Indo-Oceanic (I-O) lineages were recognized
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from human isolates. The most common patterns were Spoligo International Type Number (SIT) 53 consisting of 3 isolates accounting for 30% of the isolates. SIT44, SIT54 SIT523 were among the recognized patterns in the present finding. The patterns of four strains were not recognized by SpolDB3, the international spoligotyping database indicating that they could be new strains. The spoligotyping result of goat isolate was new to Mbovis.org strain typing database. Findings from this study add useful epidemiological data regarding human and caprine TB infection at ATJK district. Therefore, further studies must be designed to get actual profile of the disease. Diagnosis of TB should be done to the extent of strain typing so as to establish lineages particular to the region which provides easy implementation of treatment and control strategy.
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Tuberculosis, Adami Tulu