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An evaluation of Irish cattle herds with inconclusive serological evidence of bovine brucellosis.

Hayes M, Ashe S, Collins D, Power S, Kenny K, Sheahan M, O'Hagan G, More S - Ir Vet J (2009)

Bottom Line: As a result of this study, national policy has been modified to include re-sampling of all animals with CFT readings of 20 IU or greater.This project has also led to a reduction in the number of herds restricted, as well as restriction duration.It has also contributed to a reduction in the number of herds listed for contiguous tests, and therefore the potential for contiguity testing of false positive results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Veterinary Epidemiology and Risk Analysis, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. Martin.Hayes@agriculture.gov.ie.

ABSTRACT
Since 1998, there has been a steady decline in herd restrictions and de-populations in Ireland due to bovine brucellosis. There is concern that the interpretation of laboratory results may become increasingly problematic, as brucellosis prevalence falls in Ireland. Therefore, the purpose of the current study was to evaluate the infection status of Irish herds and animals with inconclusive serological evidence of bovine brucellosis. During 12 months from September 1, 2004, laboratory and observational epidemiological data were collected from all Irish herds where animal testing identified at least one animal with a complement fixation test (CFT) reading greater than zero and/or a positive result to the indirect enzyme-linked immunosorbent assay (iELISA). Due to the observational nature of the study, we have robust estimates of the relative, but not the absolute, performance of the CFT, iELISA and brucellin skin test (BST). Herds were divided into three categories (Group A, B or C) on the basis of test results at initial assessment. A total of 639 herds were enrolled into the study, and observed for at least two years following enrolment. A rising CFT titre, with a CFT reading of 111 International CFT Units (IU) or greater at the subsequent blood test, was generally associated with herds where other evidence of infection was also available. Knowledge of the CFT reading at the initial and a subsequent blood test proved useful in distinguishing false-positive and true-positive brucellosis results. There was poor correlation between the CFT and iELISA results, and between the CFT and BST results. As a result of this study, national policy has been modified to include re-sampling of all animals with CFT readings of 20 IU or greater. This project has also led to a reduction in the number of herds restricted, as well as restriction duration. It has also contributed to a reduction in the number of herds listed for contiguous tests, and therefore the potential for contiguity testing of false positive results.

No MeSH data available.


Related in: MedlinePlus

New herd restrictions and depopulations due to bovine brucellosis in Ireland during 1994 to 2007. Herd depopulation data was not available for 1994 and 1995.
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Related In: Results  -  Collection


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Figure 2: New herd restrictions and depopulations due to bovine brucellosis in Ireland during 1994 to 2007. Herd depopulation data was not available for 1994 and 1995.

Mentions: A national programme to eradicate bovine brucellosis in the Republic of Ireland commenced in 1965 with the introduction of milk ring testing for dairy herds. At the outset of the programme, 12% of the 105,000 dairy herds tested positive; a further 3% of tests were inconclusive [8]. At this time, the incidence of disease was higher in the south of Ireland than in the west and north-west. Good progress towards the goal of eradication was achieved over the following 20 years, resulting in a recorded herd prevalence of 0.19% during 1985 and 1986 [8]. Residual disease was limited to north Cork, Limerick and Tipperary. However, further progress was not achieved, with disease prevalence increasing during the 1990 s. A total of 1,081 herds were restricted during 1998 [8], with disease spreading within, not just Limerick and Tipperary, but also to counties that had been clear for a number of years. A range of policy changes were introduced from February 1998 onwards, including the re-introduction of the pre-movement test, the rapid depopulation of infected herds and the treatment of slurry with lime prior to land spreading (Figure 1). In situations where lime treatment was not possible, the herdowner was required to store the slurry or farm yard manure for a prolonged period prior to spreading. Since 1998, there has been a steady decline in herd restrictions and de-populations. In 2004, 2005, 2006 and 2007, the number of herds depopulated as a result of confirmed or suspected brucellosis was 68, 27, 3 and 0, respectively (Figure 2). If the current disease situation is maintained, Ireland will be eligible to achieve Officially Brucellosis Free (OBF) status in April 2009.


An evaluation of Irish cattle herds with inconclusive serological evidence of bovine brucellosis.

Hayes M, Ashe S, Collins D, Power S, Kenny K, Sheahan M, O'Hagan G, More S - Ir Vet J (2009)

New herd restrictions and depopulations due to bovine brucellosis in Ireland during 1994 to 2007. Herd depopulation data was not available for 1994 and 1995.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3113756&req=5

Figure 2: New herd restrictions and depopulations due to bovine brucellosis in Ireland during 1994 to 2007. Herd depopulation data was not available for 1994 and 1995.
Mentions: A national programme to eradicate bovine brucellosis in the Republic of Ireland commenced in 1965 with the introduction of milk ring testing for dairy herds. At the outset of the programme, 12% of the 105,000 dairy herds tested positive; a further 3% of tests were inconclusive [8]. At this time, the incidence of disease was higher in the south of Ireland than in the west and north-west. Good progress towards the goal of eradication was achieved over the following 20 years, resulting in a recorded herd prevalence of 0.19% during 1985 and 1986 [8]. Residual disease was limited to north Cork, Limerick and Tipperary. However, further progress was not achieved, with disease prevalence increasing during the 1990 s. A total of 1,081 herds were restricted during 1998 [8], with disease spreading within, not just Limerick and Tipperary, but also to counties that had been clear for a number of years. A range of policy changes were introduced from February 1998 onwards, including the re-introduction of the pre-movement test, the rapid depopulation of infected herds and the treatment of slurry with lime prior to land spreading (Figure 1). In situations where lime treatment was not possible, the herdowner was required to store the slurry or farm yard manure for a prolonged period prior to spreading. Since 1998, there has been a steady decline in herd restrictions and de-populations. In 2004, 2005, 2006 and 2007, the number of herds depopulated as a result of confirmed or suspected brucellosis was 68, 27, 3 and 0, respectively (Figure 2). If the current disease situation is maintained, Ireland will be eligible to achieve Officially Brucellosis Free (OBF) status in April 2009.

Bottom Line: As a result of this study, national policy has been modified to include re-sampling of all animals with CFT readings of 20 IU or greater.This project has also led to a reduction in the number of herds restricted, as well as restriction duration.It has also contributed to a reduction in the number of herds listed for contiguous tests, and therefore the potential for contiguity testing of false positive results.

View Article: PubMed Central - HTML - PubMed

Affiliation: Centre for Veterinary Epidemiology and Risk Analysis, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland. Martin.Hayes@agriculture.gov.ie.

ABSTRACT
Since 1998, there has been a steady decline in herd restrictions and de-populations in Ireland due to bovine brucellosis. There is concern that the interpretation of laboratory results may become increasingly problematic, as brucellosis prevalence falls in Ireland. Therefore, the purpose of the current study was to evaluate the infection status of Irish herds and animals with inconclusive serological evidence of bovine brucellosis. During 12 months from September 1, 2004, laboratory and observational epidemiological data were collected from all Irish herds where animal testing identified at least one animal with a complement fixation test (CFT) reading greater than zero and/or a positive result to the indirect enzyme-linked immunosorbent assay (iELISA). Due to the observational nature of the study, we have robust estimates of the relative, but not the absolute, performance of the CFT, iELISA and brucellin skin test (BST). Herds were divided into three categories (Group A, B or C) on the basis of test results at initial assessment. A total of 639 herds were enrolled into the study, and observed for at least two years following enrolment. A rising CFT titre, with a CFT reading of 111 International CFT Units (IU) or greater at the subsequent blood test, was generally associated with herds where other evidence of infection was also available. Knowledge of the CFT reading at the initial and a subsequent blood test proved useful in distinguishing false-positive and true-positive brucellosis results. There was poor correlation between the CFT and iELISA results, and between the CFT and BST results. As a result of this study, national policy has been modified to include re-sampling of all animals with CFT readings of 20 IU or greater. This project has also led to a reduction in the number of herds restricted, as well as restriction duration. It has also contributed to a reduction in the number of herds listed for contiguous tests, and therefore the potential for contiguity testing of false positive results.

No MeSH data available.


Related in: MedlinePlus