Visual and microscopic lesions of enteritis in slaughtered swine: pathogen identification and antimicrobial resistance implications

Efficient, high-quality production is essential to the swine industry, with carcass inspection by health authorities playing a crucial role in detecting abnormalities that may lead to condemnation, including enteritis. Enteritis is, usually, characterized by changes in color, mucosal integrity, intestinal wall thickness and luminal contents and has a multifactorial etiology. This study assessed and classified visual lesions attributed to enteritis and to seek for associations with known pathogens. A scoring system was applied to classify visual changes, and 30 condemned intestines were categorized as mild (< 10 points), moderate (11-20 points), or severe (> 20 points). Laboratory analyses included histopathology; isolation and antimicrobial susceptibility testing of Escherichia coli and Salmonella spp.; and molecular detection of porcine circovirus type 2 (PCV2), Lawsonia intracellularis, Brachyspira pilosicoli, and Brachyspira hyodysenteriae. Lesions were classified as mild (23%), moderate (57%), and severe (20%). PCV2 and L. intracellularis DNA were detected in 60% and 23% of samples, respectively. E. coli was isolated from 57% of intestines, of which 87% exhibited antimicrobial resistance and 56% were multidrug-resistant. No samples tested positive for Salmonella spp., B. pilosicoli, or B. hyodysenteriae. Lower condemnation scores were associated with the presence of PCV2 DNA, mild lesions, and lymph nodes showing necrosis and follicular depletion. Mild lesions were also associated with a lower frequency of multidrug-resistant E. coli. The high prevalence of antimicrobial resistance is concerning from a One Health perspective. These findings underscore the importance of pathogen monitoring, antimicrobial stewardship, and strong animal welfare practices within the swine production chain.