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

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.

Prevalence Survey of Bovine Brucellosis in Apparently Healthy Dairy Animals in Karachi, Pakistan

“…These values were quite higher (i.e., 1.84% and 1.38% by RBPT and CFT respectively) than recorded in a recent study in eastern Ethiopia (Degefu et al, 2011). However, in an Irish study, 51% prevalence of bovine brucellosis was recorded in CFT (Hayes et al, 2009). These differences might be due to different geographical locations as prevalence of bacterial diseases having been found varied from region to region (Ansari et al, 2014;Sachan et al, 2013).…”

Management practices as risk factors for the presence of bulk milk antibodies to Salmonella, Neospora caninum and Leptospira interrogans serovar hardjo in Irish dairy herds

“…Even though 82% of respondents in the present study reported that dogs had access to cow feeding and calving areas, prolonged exposure of dogs to potentially infected placentas and afterbirths would be limited as the majority of study herds calved cows in spring over a very short period of time. In addition, it should also be noted that a bovine brucellosis national eradication programme has operated in Ireland since 1965 (Hayes et al, 2009). Correct disposal of placentas and calving-related materials (e.g.…”

Outbreak of bovine brucellosis in County Clare, Ireland, in 2005

“…Details about the Irish brucellosis eradication programme have been described by Sheahan and others (2006) and Hayes and others (2009). All female and entire male cattle aged 12 months and over in Ireland are subjected to serological testing at a full herd test each year.…”

“…THERE has been a progressive drop in the herd incidence of bovine brucellosis in the Republic of Ireland since 1998 (Sheahan and others 2006, Hayes and others 2009). The number of new herd restrictions and depopulations has fallen from 1081 and 328, respectively, in 1998 to 144 and 27 in 2005.…”