# Multi-Kingdom Fecal Microbiota Alterations in Horses with Severe Equine Asthma

## TL;DR

This study finds that horses with severe asthma have altered gut microbes, which may worsen inflammation through the gut-lung connection.

## Contribution

The study identifies specific bacterial, archaeal, and fungal changes in the gut of horses with severe asthma.

## Key findings

- SEA-affected horses had lower archaeal diversity and higher Candidatus Nitrosocosmicus abundance.
- Blautia and Alternaria were less abundant in SEA-affected horses, potentially impacting metabolic and immune health.
- The gut microbiota imbalance in SEA may contribute to systemic inflammation via the gut–lung axis.

## Abstract

Severe equine asthma (SEA) is a chronic inflammation of airways affecting ~14–20% of adult horses in the Northern Hemisphere. SEA is characterized by a mixed phenotype of T helper cell responses with marked neutrophilia in the bronchoalveolar lavage fluid (BALF) of affected horses. Human studies have demonstrated the impact of gut microbiota in many diseases, including asthma susceptibility and severity. However, the potential role of the gut–lung axis in the development and persistence of SEA remains to be determined. This study aimed to identify key bacterial, archaeal, and fungal microbiota alterations in the feces of horses with severe neutrophilic asthma (n = 4) compared to healthy horses (n = 8). Archaea alpha diversity was lower in the feces of SEA-affected horses, but with high abundance of archaea genus Candidatus Nitrosocosmicus, which impacts hydrogen metabolism in horses with SEA. Other key bacterial and fungi species differences lower in SEA included Blautia and Alternaria, respectively. Blautia is associated with positive metabolic health due to its fibrolytic capabilities. Overall, our findings indicate that horses experiencing severe neutrophilic asthma have an imbalance in the intestinal microbiota that may exacerbate systemic inflammatory responses through the gut–lung axis.