C23 | Bovine tuberculosis: three years of surveillance at a slaughterhouse in the province of Bari

Purpose. Bovine tuberculosis (TB), a chronic zoonosis caused by Mycobacterium bovis, M. caprae and, more rarely, M. tuberculosis, is the subject of a national eradication plan which includes, among other measures, post-mortem inspection of slaughtered cattle. This study aims to evaluate the presence of suspected tuberculous lesions in cattle regularly slaughtered from officially TB-free farms and to determine the confirmation rate, i.e. the percentage of suspected samples that actually test positive. Methods. The study was based on the analysis of the cattle population slaughtered at a facility in the province of Bari between June 2022 and May 2025, using data extracted from the veterinary information systems portal. Data on suspected and confirmed cases of TB were also collected from the records of the Local Competent Authority. An animal was considered a “suspected case” if it had a lymph node or organ that, during post-mortem inspection, had a macroscopic lesion compatible with tuberculosis. A “confirmed case” was defined as an animal in which the presence of the mycobacterium was confirmed by real-time polymerase chain reaction, histological examination and culture of the suspected lesion. Results. During the period considered, out of a total of 5,672 cattle slaughtered, four were classified as suspected cases, of which three were confirmed (n= 2 M. bovis, n=1 M. caprae) by qPCR, histological examination and culture, and one in which M. bovis nucleic acid was preliminarily detected by qPCR, pending histological examination and culture isolation. The latter was associated with a bovine under eight months of age from a dairy farm. The confirmed cases had lesions located in the mediastinal and bronchial lymph nodes. The infected animals included two male crossbred cattle and one male buffalo. Two of the infected animals came from fattening farms, one from a dairy farm (buffalo). With regard to age, only one infected animal was over four years old, while the other two were less than eight months old. The confirmation rate in the three-year period analysed was 75%. Conclusions. This study highlights how post-mortem examination of regularly slaughtered cattle is a valuable tool for detecting tuberculous lesions in animals whose infection has not been diagnosed on the farm. The confirmation of such lesions in two subjects (one bovine and one buffalo) under eight months of age suggests that the changes to post-mortem inspection procedures introduced by Regulation (EU) 2019/627 for this age group (i.e., palpation and examination of bronchial and mediastinal lymph nodes only) may reduce the ability to detect TB cases, with possible negative repercussions on public and animal health. This consideration is particularly relevant in light of the fact that the confirmed cases also involved animals from officially disease-free farms intended for milk production. In conclusion, the observed confirmation rate is consistent with expectations and reaffirms the crucial role of the official veterinarian in the early detection of TB cases.