Oral communication in 13th International Symposium on Veterinary Epidemiology and Economics

August 23^rd, 2012

Alvarez J., Perez AM., Marques S., Bezos J., Casal C., Grau A., Minguez O., de Juan L. and Dominguez L.

In spite of progresses achieved in the last decades in the field of bovine tuberculosis (TB) diagnosis, false negative cattle remains as a major issue for disease eradication in chronically infected herds. Implementation of ancillary diagnostic tests to the single intradermal tuberculin (SIT) test, such as the interferon-gamma
(IFN-γ) assay, has increased diagnostic sensitivity, but diagnostic failures may still persist. In the present study information from post-mortem analysis of culled cattle from more than one hundred TB-infected herds from all productive types (beef, dairy and bullfighting) present in Castilla y Leon (Spain) were used to detect individual risk factors associated to M. bovis positive culture results in animals testing negative in the SIT test (strict/standard interpretation), in the IFN-γ assay (with two thresholds) and in both tests assayed in parallel. Among the risk factors evaluated, age and productive type had a crucial impact on the reliability of the SIT test for accurate detection of infected animals regardless interpretation criteria, with older negative-animals and bullfighting cattle having a significantly higher risk of yielding a positive M.
bovis culture result. The same risk factors were detected in the analysis of the IFN-γ data, but association was weaker and in the case of the age restricted only to the oldest animals (>8 years). These results demonstrate that in spite of the high sensitivity of the diagnostic strategy in place false-negative results may occur. Thus, in chronically infected herds special attention should be paid to results of older animals. Implementation of IFN-γ assay in bullfighting herds contributed to minimize the risk of diagnostic failures

	Servicio de Micobacterias (MYC). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).