Limits...
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

Risk factors and diagnostic test results at the subsequent assessment for 334 study animals in 198 Group B herds. A range of diagnostic tests are mentioned, including the complement fixation test (CFT), the indirect enzyme-linked immunosorbent assay (iELISA) and the brucellin skin test (BST).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3113756&req=5

Figure 5: Risk factors and diagnostic test results at the subsequent assessment for 334 study animals in 198 Group B herds. A range of diagnostic tests are mentioned, including the complement fixation test (CFT), the indirect enzyme-linked immunosorbent assay (iELISA) and the brucellin skin test (BST).

Mentions: A subsequent assessment, which included iELISA and CFT testing and the collection of herd-level risk factor data, was carried out, on average 25 days later, on 334 animals in 198 herds (Figure 5). The CFT results, summarised and in detail, at the initial and subsequent assessments for these 334 animals from 198 Group B herds are presented in Table 4 and Table 5, respectively. The correlation between the initial and subsequent CFT result was poor (kappa = 0.26; 0.18, 0.33; McNemar's chi square test P < 0.001; Table 4), mainly due to a falling CFT titre at the subsequent test. Of 173 animals with a positive (19.4 or greater) CFT reading at the initial assessment, 122 (70.5%) subsequently tested negative (Table 4). The iELISA results at the initial and subsequent assessments for these 334 animals from 198 Group B herds are presented in Table 6. There was poor correlation between the initial and subsequent iELISA results (kappa = 0.39; 0.31, 0.47; McNemar's chi square test P < 0.001). There was also poor correlation between the CFT and iELISA results at the subsequent assessment (kappa = -0.17; -0.25, -0.09; McNemar's chi square test P < 0.001) (Table 7). At this test, there were 56 animals in Group B herds with a positive CFT reading, including 40 (71.4%) that were also iELISA-positive.


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)

Risk factors and diagnostic test results at the subsequent assessment for 334 study animals in 198 Group B herds. A range of diagnostic tests are mentioned, including the complement fixation test (CFT), the indirect enzyme-linked immunosorbent assay (iELISA) and the brucellin skin test (BST).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Risk factors and diagnostic test results at the subsequent assessment for 334 study animals in 198 Group B herds. A range of diagnostic tests are mentioned, including the complement fixation test (CFT), the indirect enzyme-linked immunosorbent assay (iELISA) and the brucellin skin test (BST).
Mentions: A subsequent assessment, which included iELISA and CFT testing and the collection of herd-level risk factor data, was carried out, on average 25 days later, on 334 animals in 198 herds (Figure 5). The CFT results, summarised and in detail, at the initial and subsequent assessments for these 334 animals from 198 Group B herds are presented in Table 4 and Table 5, respectively. The correlation between the initial and subsequent CFT result was poor (kappa = 0.26; 0.18, 0.33; McNemar's chi square test P < 0.001; Table 4), mainly due to a falling CFT titre at the subsequent test. Of 173 animals with a positive (19.4 or greater) CFT reading at the initial assessment, 122 (70.5%) subsequently tested negative (Table 4). The iELISA results at the initial and subsequent assessments for these 334 animals from 198 Group B herds are presented in Table 6. There was poor correlation between the initial and subsequent iELISA results (kappa = 0.39; 0.31, 0.47; McNemar's chi square test P < 0.001). There was also poor correlation between the CFT and iELISA results at the subsequent assessment (kappa = -0.17; -0.25, -0.09; McNemar's chi square test P < 0.001) (Table 7). At this test, there were 56 animals in Group B herds with a positive CFT reading, including 40 (71.4%) that were also iELISA-positive.

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