Comparative evaluation of post-mortem methods for detection of diarrhoea in early-life piglets

Identifying evidence of peri-mortem diarrhoea during necropsy is important for both clinical herd management and research. In live pigs, diarrhoea is typically assessed by inspection of faecal pools on the pen floor scoring of faecal rectal samples, including cotton-swabs, but these methods depend on the availability of faecal material and are therefore often not applicable at necropsy. This study aimed to evaluate intestinal content characteristics and perianal faecal staining as post-mortem indicators of peri-mortem diarrhoea. These indicators were compared with cotton-swab faecal scoring using faecal dry-matter content as a reference. Furthermore, associations with enteric pathogens detected by PCR were investigated.

A total of 145 pigs from a Danish commercial herd were monitored from birth until 10 weeks of age and euthanised in age-stratified batches for post-mortem examinations. Intestinal content from duodenum, jejunum, ileum, caecum, and colon was evaluated for consistency and colour using categorical scales and compared with perianal faecal staining, faecal scores obtained by the cotton-swab method, faecal dry-matter percentage, and pathogen detections in faecal samples by high-throughput real-time PCR. Colonic content consistency and perianal faecal staining were strongly associated, and in all pigs with watery colonic content a perianal faecal staining was observed. Colonic content consistency corresponded well with faecal dry-matter percentage categories, with mucoid, runny and watery consistencies indicating diarrheic cases (sensitivity: 87%, specificity: 55%). Jejunal content consistency showed little to no association with cotton-swab faecal scores, indicating limited value as an indicator of peri-mortem diarrhoea. Pre-weaning piglets predominantly showed lighter (yellow-green), firmer intestinal contents, whereas post-weaning animals displayed darker and looser contents, particularly in the large intestine. Interobserver reliability was high for consistency scoring (Krippendorff's α > 0.80 across most segments) but low for colour scoring (α < 0.64). Dark colonic content was associated with PCR detection of Lawsonia intracellularis and Brachyspira pilosicoli, while yellow coloration showed an indirect association with detection of Clostridium perfringens α and β2 toxin genes.

Post-mortem assessment of colonic content consistency represent a promising, practical and reproducible indicator of peri-mortem diarrhoea, but tending to identify a higher prevalence of diarrheic cases compared to diarrhoea defined by dry-matter percentage. Colonic content consistency also showed a strong association with perianal faecal staining. In contrast, jejunal content consistency showed no diagnostic value as an indicator of peri-mortem diarrhoea. Visual assessment of intestinal content colour demonstrated poor interobserver reproducibility, and any observed associations with enteric pathogens should therefore be interpreted with caution. Overall, these findings support the use of colonic content consistency and perianal faecal staining as necropsy-based indicators for detection of peri-mortem diarrhoea.