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Evidence for genetic variance in resistance to tuberculosis in Great Britain and Irish Holstein-Friesian populations.

Bermingham ML, Brotherstone S, Berry DP, More SJ, Good M, Cromie AR, White IM, Higgins IM, Coffey M, Downs SH, Glass EJ, Bishop SC, Mitchell AP, Clifton-Hadley RS, Woolliams JA - BMC Proc (2011)

Bottom Line: The estimated heritability of susceptibility to TB, as judged by responsiveness to the SICTT, was 0.16 (0.012) and 0.14 (0.025) in the GB and Irish populations, respectively.Estimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB.Epidemiological analysis suggests that factors such as variation in exposure or imperfect sensitivity and specificity would have resulted in underestimation of the true values.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Roslin Institute, Roslin Biocentre, Roslin, Midlothian EH25 9RG, UK. Mairead.Bermingham@roslin.ed.ac.uk.

ABSTRACT

Background: Here, we jointly summarise scientific evidence for genetic variation in resistance to infection with Mycobacterium bovis, the primary agent of bovine tuberculosis (TB), provided by two recent and separate studies of Holstein-Friesian dairy cow populations in Great Britain (GB) and Ireland.

Methods: The studies quantified genetic variation within archived data from field and abattoir surveillance control programmes within each country. These data included results from the single intradermal comparative tuberculin test (SICTT), abattoir inspection for TB lesions and laboratory confirmation of disease status. Threshold animal models were used to estimate variance components for responsiveness to the SICTT and abattoir confirmed M. bovis infection. The link functions between the observed 0/1 scale and the liability scale were the complementary log-log in the GB, and logit link function in the Irish population.

Results and discussion: The estimated heritability of susceptibility to TB, as judged by responsiveness to the SICTT, was 0.16 (0.012) and 0.14 (0.025) in the GB and Irish populations, respectively. For abattoir or laboratory confirmation of infection, estimates were 0.18 (0.044) and 0.18 (0.041) from the GB and the Irish populations, respectively.

Conclusions: Estimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB. Epidemiological analysis suggests that factors such as variation in exposure or imperfect sensitivity and specificity would have resulted in underestimation of the true values.

No MeSH data available.


Related in: MedlinePlus

Cumulative distribution of individual risk in herd breakdowns derived from a normal approximation to the models fitted, within the GB (black) and Irish (grey) datasets. x-axis = risk threshold, y-axis = proportion of animals in the herd with risk below the threshold.
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Figure 1: Cumulative distribution of individual risk in herd breakdowns derived from a normal approximation to the models fitted, within the GB (black) and Irish (grey) datasets. x-axis = risk threshold, y-axis = proportion of animals in the herd with risk below the threshold.

Mentions: Individuals within herd breakdowns were found to have differing probabilities of responding to the SICTT in the two studies (Figure 1). In the GB study the most susceptible five percent of the cows had an estimated risk of ≥0.29 of being culled as a reactor, whereas in the Irish study the equivalent group of cows had a somewhat higher estimated risk, ≥0.48, of exhibiting a standard reaction to the SICTT. This may be an indication that the cows in the GB study were less likely to respond to the SICTT following exposure to M. bovis, or that the Irish cows had a greater opportunity for exposure (average herd breakdown reactor prevalence was 7% in the GB data set, as compared to 10% standard reactor prevalence in the Irish dataset) and hence had a greater opportunity for trait expression than the GB cows.


Evidence for genetic variance in resistance to tuberculosis in Great Britain and Irish Holstein-Friesian populations.

Bermingham ML, Brotherstone S, Berry DP, More SJ, Good M, Cromie AR, White IM, Higgins IM, Coffey M, Downs SH, Glass EJ, Bishop SC, Mitchell AP, Clifton-Hadley RS, Woolliams JA - BMC Proc (2011)

Cumulative distribution of individual risk in herd breakdowns derived from a normal approximation to the models fitted, within the GB (black) and Irish (grey) datasets. x-axis = risk threshold, y-axis = proportion of animals in the herd with risk below the threshold.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108209&req=5

Figure 1: Cumulative distribution of individual risk in herd breakdowns derived from a normal approximation to the models fitted, within the GB (black) and Irish (grey) datasets. x-axis = risk threshold, y-axis = proportion of animals in the herd with risk below the threshold.
Mentions: Individuals within herd breakdowns were found to have differing probabilities of responding to the SICTT in the two studies (Figure 1). In the GB study the most susceptible five percent of the cows had an estimated risk of ≥0.29 of being culled as a reactor, whereas in the Irish study the equivalent group of cows had a somewhat higher estimated risk, ≥0.48, of exhibiting a standard reaction to the SICTT. This may be an indication that the cows in the GB study were less likely to respond to the SICTT following exposure to M. bovis, or that the Irish cows had a greater opportunity for exposure (average herd breakdown reactor prevalence was 7% in the GB data set, as compared to 10% standard reactor prevalence in the Irish dataset) and hence had a greater opportunity for trait expression than the GB cows.

Bottom Line: The estimated heritability of susceptibility to TB, as judged by responsiveness to the SICTT, was 0.16 (0.012) and 0.14 (0.025) in the GB and Irish populations, respectively.Estimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB.Epidemiological analysis suggests that factors such as variation in exposure or imperfect sensitivity and specificity would have resulted in underestimation of the true values.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Roslin Institute, Roslin Biocentre, Roslin, Midlothian EH25 9RG, UK. Mairead.Bermingham@roslin.ed.ac.uk.

ABSTRACT

Background: Here, we jointly summarise scientific evidence for genetic variation in resistance to infection with Mycobacterium bovis, the primary agent of bovine tuberculosis (TB), provided by two recent and separate studies of Holstein-Friesian dairy cow populations in Great Britain (GB) and Ireland.

Methods: The studies quantified genetic variation within archived data from field and abattoir surveillance control programmes within each country. These data included results from the single intradermal comparative tuberculin test (SICTT), abattoir inspection for TB lesions and laboratory confirmation of disease status. Threshold animal models were used to estimate variance components for responsiveness to the SICTT and abattoir confirmed M. bovis infection. The link functions between the observed 0/1 scale and the liability scale were the complementary log-log in the GB, and logit link function in the Irish population.

Results and discussion: The estimated heritability of susceptibility to TB, as judged by responsiveness to the SICTT, was 0.16 (0.012) and 0.14 (0.025) in the GB and Irish populations, respectively. For abattoir or laboratory confirmation of infection, estimates were 0.18 (0.044) and 0.18 (0.041) from the GB and the Irish populations, respectively.

Conclusions: Estimates were all significantly different from zero and indicate that exploitable variation exists among GB and Irish Holstein Friesian dairy cows for resistance to TB. Epidemiological analysis suggests that factors such as variation in exposure or imperfect sensitivity and specificity would have resulted in underestimation of the true values.

No MeSH data available.


Related in: MedlinePlus