Genotyping of Equine Lawsonia intracellularis Sampled in Japan by Using Multilocus Variable-Number Tandem Repeat Analysis.

The research article explores the increasing rate of equine proliferative enteropathy, a disease caused by Lawsonia intracellularis, worldwide. Genotyping was conducted on various samples, but found no clear correlation between the disease and the age or clinical condition of the horses. However, the methods used offer potential for understanding how the disease spreads.

Overview of the Study

• The researchers conducted multilocus variable-number tandem repeat analysis (MLVA) on 130 samples of Lawsonia intracellularis, a bacterium known to cause equine proliferative enteropathy—a disease that affects horses’ intestines. Samples came from different sources: horses, pigs, wildlife, one vaccine strain, and 17 public strains.
• The main goal of the study was to investigate if there is a relationship between variable-number tandem repeat (VNTR) patterns, which refer to the number and sequence of repeats in a DNA sequence, and the host species or clinical status of horses affected by this disease.

Findings of the Study

• The results showed a high diversity of VNTR patterns: out of 130 samples, 99 different patterns were identified, with the 98 horse samples falling into 71 distinct patterns.
• The researchers constructed a phylogenetic tree— a branching diagram or “tree” showing the evolutionary relationships among various biological species—based on the results of the MLVA. The tree showed three clusters: porcine (pigs), equine (horses), and a miscellaneous group.
• The equine cluster contained 46 horse samples, with most (91.3%) collected from two specific areas, indicating a geographically localized distribution of certain VNTR patterns.

Conclusion

• The study found no significant relation between the VNTR patterns and the age or clinical condition of the horses. In other words, the genetic variation of L. intracellularis did not appear to correlate with the severity or type of symptoms seen in horses.
• Through MLVA, horse samples could be discriminated from pig samples, however, horse samples in the miscellaneous cluster were indistinguishable from wildlife samples. This implies that interspecific transmission of L. intracellularis between horses and wildlife might be possible, although this needs further investigation.
• The researchers concluded that whilst the MLVA method may not give insight into the clinical status of horses with equine proliferative enteropathy, it may still be valuable for investigating the epidemiology and transmission pathways of this disease, contributing to efforts to manage it more effectively.