When Is really Specific Enough? Evaluating The Specificity Of Single And Comparative Skin Tests In Tuberculosis-free Herds Using Field And Experimental Data
Comunicación oral en 17th International Symposium of Veterinary Epidemiology and Economics (ISVEE 17)
11 de noviembre de 2024
Gómez-Buendía A., Diez-Guerrier A., Munoz M., Saez JL., Romero B. y Alvarez J.
The implementation of the bovine tuberculosis (bTB) eradication program in Spain has allowed 19 out of 52 provinces, representing about 40% of the cattle population, to reach the status of officially bTBfree (OTF). In this context the use of highly specific tests that can minimize the culling of reactors and other avoidable costs of cross-reactions is crucial. Although skin tests routinely used for bTB are considered highly specific, studies on their performance in Spain have focused on sensitivity, and thus there is a knowledge gap regarding how these tests can perform in OTF populations and factors that may impact their performance.
Here, two datasets were analyzed to assess the specificity of skin tests under field conditions: one containing results from 3039 animals in 46 OTF herds tested by the authors in a high-prevalence bTB region, and another with data from more than 3.5 million animals in 23,931 farms tested over six years in a low-prevalence/OTF region. Bayesian hierarchical models were used to estimate the probability of cross-reaction at the animal and herd levels adjusting for covariates at both levels (age, sex, herd size, production type, location, and diagnostic test date).
Individual and herd-level median estimates ranged from 96.9 to 98.7% and 69.3 to 94.3% respectively, somewhat lower than published estimates. Positive results were four times more likely in older animals (> 5 years) and almost twice as likely in dairy and small herds (< 30 animals) and in animals tested in winter and spring. Temporal trends were also identified.
These results indicate that although single and comparative skin tests are generally highly specific, certain factors can affect their reliability, especially at the herd level. Recognizing these factors in an OTF context is essential for the effective application of these tests
 | Servicio de Micobacterias (MYC). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM). |
 | Servicio de Sanidad Animal. Consellería do Medio Rural. Xunta de Galicia. |
 | Subdirección General de Sanidad e Higiene Animal y Trazabilidad. Dirección General de la Producción Agraria. Ministerio de Agricultura, Pesca y Alimentación (MAPA). |
Enlace a 17th International Symposium of Veterinary Epidemiology and Economics (ISVEE 17)
