Mycobacterium bovis genotypes in Northern Ireland: herd‐level surveillance (2003 to 2008)

Abstract

Surveillance genotyping (variable number tandem repeat profiling and spoligotyping) of Mycobacterium bovis isolates from culture-confirmed bovine tuberculosis (TB)-affected herds in Northern Ireland is presented for the years 2003 to 2008 inclusive. A total of 175 M bovis genotypes were identified in 8630 isolates from 6609 herds. On average, 73 genotypes were identified each year, with 29 genotypes present in all six years. Highly significant differences (P<0.0001) were observed between the relative frequency of some genotypes in the years 2003 to 2008. The spatial distribution of M bovis genotypes was not random (P<0.0001). Significant geographical localisation of M bovis genotypes was evident, suggesting that sources tended to be local. Despite regions being dominated by geographically localised genotypes, substantial and exploitable local diversity was still evident. Genotypes were also translocated significant distances from their normal geographical location.

Splitting of a Prevalent Mycobacterium bovis Spoligotype by Variable-Number Tandem-Repeat Typing Reveals High Heterogeneity in an Evolving Clonal Group

“…The MIRU-VNTR characterization of this random panel of M. bovis SB0121 isolates revealed a high degree of diversity. This is consistent with previous reports from Portugal (12,13) and Italy (10) where the MIRU-VNTR type diversity of the most prevalent spoligotypes (SB0121 and SB0120, respectively) is high compared to that of the European 1 clonal complex in the United Kingdom and the Republic of Ireland (34). The underlying reasons for this high diversity in the Iberian M. bovis population remain unknown.…”

“…These studies showed that high levels of discrimination could be achieved by spoligotyping (discriminatory index [D] ϭ 0.89 and 0.87 in Portugal and Spain, respectively), although subsequent studies from Portugal found that discrimination actually increased with MIRU-VNTR typing (12,13).…”

“…However, in some geographical settings, this cost-effective high-throughput technique does not offer adequate discrimination (2,3,4) and is thus complemented with mycobacterial interspersed repetitive-unit-variablenumber tandem-repeat (MIRU-VNTR) typing (5,6). The MIRU-VNTR technique has been evaluated in many countries using different sets of makers (2,4,(7)(8)(9)(10)(11)(12)(13)(14)(15).…”

Risk factors for failure to detect bovine tuberculosis in cattle from infected herds across Northern Ireland (2004–2010)

“…Herd size has been found to be a significant risk factor for bTB disclosure and herd breakdown risk in a number of studies (Brooks-Pollock and Keeling, 2009;Byrne et al, 2014;Doyle et al, 2014;Skuce et al, 2010). Herd size may contribute to increased bTB risk due to the potential for increased residual infection, especially if tests can behave differentially across herd sizes.…”

“…The NI cut-off is more stringent interpretation using a lower optical density threshold (PPDB-PPDA OD = 0.05 if PPDB OD ≥ 0.1), increasing the sensitivity of the test, but reducing the specificity of the test in comparison to the commercial test cut-off (OD = 0.1). (Roring et al, 2000;Skuce et al, 2010).…”