Use this URL to cite or link to this record in EThOS:
Title: Molecular epidemiology of Mycobacterium bovis in cattle in Iran
Author: Tadayon, K.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2007
Availability of Full Text:
Access from EThOS:
Mycobacterium bovis causes bovine tuberculosis (BTB) that is an endemic disease of cattle in Iran. Despite benefiting from a successful test-and-slaughter programme, initiated in the late 1960s, which has reduced the prevalence to 0.05% (reactors in tuberculinated cattle) in 2006, there is little known about the epidemiology of M. bovis in Iran. The present study sought to improve this serious lack of information through combining traditional diagnostic methods (tuberculin tests in the field, mean inspections in abattoirs and microbiology in the laboratory) with modern molecular speciation and strain typing (Region of Deletion (RD) typing, spoligotyping and Variable Number Tandem Repeat (VNTR) typing). With information collected, a second objective of this thesis has been the analysis of historic field and recent laboratory observations to elaborate the origins of M. bovis in Iran and consequently developing a scenario for the history of BTB in this country. Molecular identification of 133 mycobacterial isolates collected from abattoir specimens confirmed M. bovis as the single principal cause of BTB in the Iranian environment. None of the studied isolates were M. bovis BCG and this categorically ruled out concerns over interpretation of the tuberculin test in cattle due to unauthorised vaccination of cattle with BCG vaccine in Iran.  Spoligotyping revealed a genetically homogenous population of M. bovis. Only eight, highly similar, spoligotypes were identified with five of them not previously seen elsewhere. The ancestral, BCG-like spoligotype, SB0120, was the most prevalent (41%) along with two other similar patterns, SB1167 (39%) and SB1168 (17%) which were unique to Iran. VNTR typing recognised 23 types and again revealed a homogenous population with only a few predominant patterns. Generally speaking, the same genotypes of M. bovis were found to infect both European breeds and zebu bovids in Iran. The homogeneity of the M. bovis population, portrayed by this study, was unexpected. This lack of diversity is probably a reflection of the significant increase in population of BTB susceptible, Holstein-Friesian cattle in the last fifty years. The absence of adequate initial BTB control measures could have led to the rapid clonal expansion of a SB0120 strain which subsequently diversified into a few highly related strains. Whilst the origin of this strain might be from outwith Iran, the origins of the others are likely to have been within Iran and those Iranian spoligotypes that are also reported elsewhere in the world are most likely to be due to convergent evolution (homoplasy) rather than to common epidemiology.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available