Dysbiosis is not present in horses with fecal water syndrome when compared to controls in spring and autumn

Abstract

Background: Fecal water syndrome (FWS) is long-standing and common in horses, particularly in central Europe. No large epidemiological data sets exist, and the cause remains elusive. Dysbiosis could play a role in pathogenesis.

Objectives: To evaluate whether dysbiosis is present in horses with FWS when compared to stable-matched control horses in spring and autumn.

Animals: Fecal samples were collected from horses with FWS (n = 16; 9 mares, 7 geldings) and controls (n = 15; 8 mares, 7 geldings).

Methods: The bacterial microbiome of samples collected in spring and autumn of 2016 was analyzed using high-throughput sequencing. Differences in relative abundance of bacterial taxa, alpha diversity, and beta diversity indices were assessed between horses with FWS and controls based on season.

Results: Differences in microbial community composition based on time point and health status were not observed on any taxonomic level. Limited differences were seen on linear discriminant analysis effect size analysis. No difference in alpha diversity indices was observed including richness, diversity based on health status, or time point. No effect of health status on microbial community membership structure was observed.

Conclusions and clinical importance: Limited differences were found in the bacterial microbiota of horses with and without FWS, regardless of season. Further research is needed to elucidate the role of microbiota in the development of FWS.

Keywords: clostridiales; fecal water syndrome; gastrointestinal microbiota; horse; metagenomic sequencing.

FIGURE 1

Relative abundance of A, phyla, B, classes, and C, orders of horses with and without fecal water syndrome sampled in autumn and spring. Other includes taxa with a relative abundance of <1%. In spring, 15 and 16 horses with and without fecal water were sampled, respectively; in autumn, 9 and 7 horses with and without fecal syndrome were sampled, respectively

FIGURE 2

Species significantly enriched in the bacterial microbiota of horses with (red) and without (blue) fecal water syndrome sampled in A, spring and B, autumn determined by linear discriminant analysis effect size (LEfSe). In spring, 15 and 16 horses with and without fecal water were sampled, respectively; in autumn, 9 and 7 horses with and without fecal syndrome were sampled, respectively

FIGURE 3

Principal coordinate analysis of the fecal bacterial microbiota of horses with and without fecal water syndrome sampled in spring (A, B) and autumn (C, D). Principal coordinate analysis based on the Jaccard index in spring (B) and autumn (D) and the Yue and Clayton index in spring (A) and autumn (C); red: fecal water syndrome, blue: control. Each symbol represents a farm (disease/control pairs). In spring, 16 and 15 horses with and without fecal water were sampled, respectively; in autumn, 8 and 7 horses with and without fecal syndrome were sampled, respectively. Each symbol represents a farm, in 2 farms 2 horses were compared to 1 control and in 1 farm 1 horse was compared to 2 controls