Zoonotic transmission of Mycobacterium tuberculosis complex between cattle and humans in Central Ethiopia

Tefera Woldemariam ¹ Temesgen Mohammed ^2* Aboma Zewude ² Mahlet Chanyalew ³ Hazim Khalifa ² Gezahegne Mamo Kassa ⁴ Gobena Ameni ^2*

• ¹ School of Veterinary Medicine, Hawassa University, Hawassa, Ethiopia
• ² Department of Veterinary Medicine, College of Food and Agriculture, United Arab Emirates University, AlAin, Abu Dhabi, United Arab Emirates
• ³ Aklilu Lemma Institute of Pathobiology, Addis Ababa University, Addis Ababa, Addis Ababa, Ethiopia
• ⁴ College of Veterinary Medicine and Agriculture, Addis Ababa University, Bishoftu, Ethiopia

The zoonotic transmission of tuberculosis (TB) from cattle to humans has long been recognized while its reverse zoonotic transmission from humans to animals has recently been reported.The socioeconomic situations of the rural communities of Ethiopia are conducive for the zoonotic and reverse zoonotic transmission of TB between cattle and human. The objective of this study was to investigate the transmission of Mycobacterium tuberculosis complex between cattle and humans in Central Ethiopia.To achieve this objective a cross-sectional study was conducted on 1896 cattle slaughtered in two abattoirs and 392 TB suspicious human subjects visiting health institutions for treatment.Mycobacteriological culture and spoligotyping were used for the study. In addition, the Spoligotype International Types and VNTR (variable number of DNA tandem repeats) International Types (SITVIT2) database and the online "Run TB-Lineage" were used to identify SIT and lineages of the human and cattle isolates.Results: Culture positivity was found in 26.3% (21/80) of the gross TB suspicious tissue lesions of cattle of the lungs and lymph node (mandibular, retropharyngeal, cranial and caudal mediastinal, left and right bronchial, hepatic, and mesenteric lymph nodes). Of the 21 cattle isolates, 12 (57.2%) were M. bovis while the remaining 9 (42.8%) were M. tuberculosis. Similarly, only 22% (86/392) of the sputa samples from TB suspicious humans were culture positive. These 86 human isolates were classified into 81 M.tuberculosis, three M. africanum and two M. bovis by spoligotyping. SIT50, SIT118 and SIT1318 which belong to the human species were isolated from both humans and cattle. The two human M. bovis isolates had the pattern of SB1443, which was not isolated from cattle in this study area.The zoonotic and reverse zoonotic transmissions of TB were confirmed in Ethiopia by the isolation of two M. bovis from human and isolation of nine M. tuberculosis from cattle, which suggested higher role of M. tuberculosis in cattle compared to the role of M. bovis in humans.