Relationship between ambient temperature at sampling and the interferon gamma test result for bovine tuberculosis in cattle

Bisschop, P.I.H.; Frankena, K.; Milne, Georgina; Ford, Tom; McCallan, Lyanne; Young, Fiona; Byrne, Andrew

doi:10.1016/j.vetmic.2023.109778

Cited by 1 publication

(1 citation statement)

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“…Interestingly, these differences were observed despite using the same tuberculin for stimulation of all the blood samples regardless of their origin, thus removing the variability associated with the use of different tuberculins in different countries, a well-known factor influencing bTB diagnostic performance [ 55 ]. Season could influence the performance of the IFN-γ due to the possible impact of environmental conditions on the viability of the samples [ 21 , 56 ] and the occurrence of non-specific immunological stimuli [ 57 ]. All samples were collected between November and February except those from region E, in which animals were sampled between May and June.…”

Section: Discussionmentioning

confidence: 99%

Evaluation of the performance of the IFN-γ release assay in bovine tuberculosis free herds from five European countries

Gomez-Buendia,

Romero,

Bezos

et al. 2023

Vet Res

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The diagnostic methods for granting and maintenance of the official tuberculosis-free (OTF) status and for intra-Community movement of cattle are the tuberculin skin tests (single or comparative) and the interferon-γ (IFN-γ) release assay (IGRA). However, until now, IGRAs have been primarily applied in infected farms in parallel to the skin test to maximize the number of infected animals detected. Therefore, an evaluation of the performance of IGRAs in OTF herds to assess whether if their specificity is equal to or higher than that of the skin tests is needed. For this, a panel of 4365 plasma samples coming from 84 OTF herds in six European regions (five countries) was assembled and analysed using two IGRA kits, the ID Screen® Ruminant IFN-g (IDvet) and the Bovigam™ TB Kit (Bovigam). Results were evaluated using different cut-offs, and the impact of herd and animal-level factors on the probability of positivity was assessed using hierarchical Bayesian multivariable logistic regression models. The percentage of reactors ranged from 1.7 to 21.0% (IDvet: S/P ≥ 35%), and 2.1–26.3% (Bovigam: ODbovis–ODPBS ≥ 0.1 and ODbovis–ODavium ≥ 0.1) depending on the region, with Bovigam disclosing more reactors in all regions. The results suggest that specificity of IGRAs can be influenced by the production type, age and region of origin of the animals. Changes in the cut-offs could lead to specificity values above 98–99% in certain OTF populations, but no single cut-off yielding a sufficiently high specificity (equal or higher than that of skin tests) in all populations was identified. Therefore, an exploratory analysis of the baseline IFN-γ reactivity in OTF populations could help to assess the usefulness of this technique when applied for the purpose of maintaining OTF status.

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