Comparison of feces versus rectal swabs for the molecular detection of Lawsonia intracellularis in foals with equine proliferative enteropathy.

The research article compares the effectiveness of using fecal samples versus rectal swabs for detecting the bacterium Lawsonia intracellularis in foals that may have equine proliferative enteropathy (EPE), a disease that affects the intestines. The study found that feces yielded similar detection results but carried a higher bacterial load than rectal swabs, both contributing towards a combined detection rate of 90%.

Methodology

• The study involved 42 foals suspected of having EPE. Both fecal samples and rectal swabs were collected from each foal as the basis for the comparison.
• The samples were processed for DNA purification using an automated extraction system.
• The purified DNA was then examined using real-time polymerase chain reaction (PCR) to look for the presence of the aspartate ammonia lyase (aspA) gene of L. intracellularis.
• Quantitative measurements of the aspA gene were performed using a standard curve for L. intracellularis, and the results were presented as the copy number of the gene per microliter of purified DNA.

Results

• The combined PCR detection rate for L. intracellularis was 90%, with 38 of the 42 foals testing positive in either feces or rectal swabs or both.
• Six foals specifically tested PCR-positive only in feces, while five others tested positive only in rectal swabs.
• Overall, the fecal samples yielded a higher copy number of the aspA gene of L. intracellularis compared to the rectal swabs. Hence, feces were found to have a higher bacterial load for L. intracellularis.
• Four foals test results were negative for L. intracellularis in both feces and rectal swabs.

Conclusion

• The findings suggest that both fecal samples and rectal swabs yield similar PCR-positive results for L. intracellularis, but the bacterial load was significantly higher in feces.
• By testing both types of samples, the PCR detection rate for L. intracellularis increased from approximately 76%-79% (for each sample type separately) to 90% (when combined).
• Considering these findings, the study recommends the consideration of rectal swabs as an alternative sample type for suspected cases of EPE, particularly in foals with decreased or no fecal output.