Blood amino acid changes associated with Lawsonia intracellularis infection in horses.

Background: Hypoproteinaemia/hypoalbuminaemia is a typical clinical feature of Lawsonia intracellularis infection in horses, but amino acid perturbations in these horses have not been investigated.

Objectives: Clarifying blood amino acid levels in horses suffering from Lawsonia intracellularis infection to identify novel aspects of the disease.

Study design: Retrospective observational study.

Methods: A total of 135 serum samples collected from horses from 59 farms were used in this study. Horses diagnosed with the clinical form of equine proliferative enteropathy (EPE) were enrolled as a clinical group (n = 46). Clinically normal herd mates of EPE patients were assigned to a subclinical EPE group (n = 22) or Lawsonia intracellularis exposure group (n = 41). Horses from EPE-naïve farms were used for control horses (n = 26). Amino acid profiles of each group were reviewed through principal component analysis, and subsequently, the Steel-Dwass multiple comparison test or Tukey's honestly significant difference test was used to clarify substantial amino acid changes characteristic of the horse populations.

Results: Significant perturbations in amino acid concentrations were observed in horses with clinical and subclinical forms of the disease and in the exposure group compared to control horses. Asparagine, glutamine, aspartic acid, glutamic acid, and glycine were significantly perturbed in the clinical, subclinical, and exposure groups compared to the control group, while alanine, citrulline, and tryptophan were characteristically perturbed in the clinical group relative to the other horse groups.

Main limitations: Variability of the original farms from which study populations were derived due to the retrospective nature of the study might have influenced the aminogram.

Conclusions: Amino acid concentrations show substantial perturbations in relation to the clinical status of EPE. Evaluation of the aminograms of horses with Lawsonia intracellularis infection provides novel information on this disease, which would be of clinical and, potentially, therapeutic relevance.