Bayesian latent class estimation of sensitivity and specificity parameters of diagnostic tests for bovine tuberculosis in chronically infected herds in Northern Ireland

Abstract

In the European Union, the recommended ante-mortem diagnostic methods for bovine tuberculosis (bTB) include the single intradermal cervical comparative tuberculin (SICCT) test and the interferon-gamma (IFN-γ) test as an ancillary test. The SICCT test has a moderate sensitivity (Se) and high specificity (Sp), while the IFN-γ test has good Se, but a lower Sp than the SICCT test. A retrospective Bayesian latent class analysis was conducted on 71,185 cattle from 806 herds chronically infected with bTB distributed across Northern Ireland (NI) to estimate the Se and Sp of the common ante-mortem tests and meat inspection. Analyses were also performed on data stratified by farming type and herd location to explore possible differences in test performance given the heterogeneity in the population. The mean estimates in chronically infected herds were: (1) 'standard' SICCT: Se 40.5-57.7%, Sp 96.3-99.7%; (2) 'severe' SICCT: Se 49.0%-60.6%, Sp 94.4-99.4%; (3) IFN-γ(bovine-avian) using a NI optical density (OD) cut-off difference of 0.05: IFN-γ(B-A): Se 85.8-93.0%, Sp 75.6-96.2%; (4) IFN-γ(bovine-avian) using a standard 'commercial' OD cut-off difference of 0.1: IFN-γ(B-A): Se 83.1-92.1%, Sp 83.1-97.3%; and (5) meat inspection: Se 49.0-57.1% Se, Sp 99.1-100%. Se estimates were lower in cattle from dairy farms than from beef farms. There were no notable differences in estimates by location of herds. Certain population characteristics, such as production type, might influence the ability of bTB tests to disclose truly infected cases.

Liver fluke (Fasciola hepatica) co‐infection with bovine tuberculosis (bTB) in cattle: A retrospective animal‐level assessment of bTB risk in dairy and beef cattle

“…; Lahuerta‐Marin et al. ). For example, the Single Intradermal Comparative Tuberculin Test (SICTT), the standard test used in the United Kingdom and ROI exhibits high mean specificity (>99%; de la Rua‐Domenech et al.…”

“…; Nuñez‐Garcia et al. ; Lahuerta et al., ). This means, the test performs well in terms of not disclosing false‐positive animals (an economic cost), but may leave truly infected animals on farm (an epidemiologic risk).…”

“…; Clegg et al. ; Lahuerta et al., ), but moderate mean sensitivity (50%–80%; De la Rua‐Domenech et al., ; Clegg et al. ; Nuñez‐Garcia et al.…”

“…Compounding this problem is the fact that tests used to identify infected cattle exhibit nonperfect test characteristics (De la Rua-Domenech et al 2006;McCallan et al 2017;Lahuerta-Marin et al 2018). For example, the Single Intradermal Comparative Tuberculin Test (SICTT), the standard test used in the United Kingdom and ROI exhibits high mean specificity (>99%; de la Rua- Domenech et al 2006;Clegg et al 2011;Lahuerta et al, 2018), but moderate mean sensitivity (50%-80%; De la Rua-Domenech et al, 2006;Clegg et al 2011;Nuñez-Garcia et al 2018;Lahuerta et al, 2018). This means, the test performs well in terms of not disclosing false-positive animals (an economic cost), but may leave truly infected animals on farm (an epidemiologic risk).…”

Assessment of the bovine tuberculosis elimination protocol in the United States

“…Animal BW is mainly a function of age, lactation, and pregnancy. It is estimated following the functions of Korver et al (1985), as described in the Nutrient Requirements of Dairy Cattle (NRC, 2001).…”