Abstract
Background Recent evidence suggests that an altered intestinal microbiota, specifically a reduction of bacterial diversity or a shift in microbial composition, is associated with the development of hypersensitivity disorders in humans, but this is unknown for horses. Objectives In this study we hypothesized that horses affected by either Culicoides hypersensitivity or severe equine asthma or both show a decreased diversity of their intestinal microbiota. We also investigated environmental effects. Methods Rectal swab samples of a total of 140 horses were collected and the owners completed a detailed questionnaire about their horse. For each allergic horse, a healthy peer from the same stable was equally sampled as an environmentally matched control. Microbiota in the swabs was determined by assessing the V4 region of the bacterial 16S rRNA gene. Structures of bacterial communities were investigated by means of alpha and beta diversity indices. Results Group wise comparisons between healthy and allergic horses showed no significant differences regarding alpha (p = 0.9) and beta diversity (p = 0.5). However, the microbial structure was associated with environmental factors such as the type of stable (p = 0.001), access to pasture (p = 0.001) or the type of feeding (p = 0.003). There was also a strong location effect meaning that the microbiota was more similar within the same as compared between farms within this study. Conclusion Our observations suggest that hypersensitivity disorders in adult horses are not associated with an alteration of the intestinal microbiota, but environmental and/or location factors strongly influence these bacteria.
Highlights
There is recent evidence for a role of the intestinal microbiome in the development and maintenance of hypersensitivity disorders
Three study groups were formed: horses suffering from Culicoides Hypersensitivity, horses suffering from severe equine asthma and horses suffering from both disorders
The horses originated from altogether 48 farms from all over Switzerland and further details about each horse can be found in the supplementary material (Additional Table A1)
Summary
There is recent evidence for a role of the intestinal microbiome in the development and maintenance of hypersensitivity disorders. Early infancy is a critical period of microbiological and immunological development (Fujimura and Lynch 2015) and an imbalance in the bacterial composition at this time may lead to an increased risk of allergic sensitization (Legatzki et al 2014; Rutten et al 2015) In human medicine this has been shown for several allergic disorders, like asthma, rhinitis or atopic dermatitis (Bottcher et al 2000; Bisgaard et al 2011; Abrahamsson et al 2014; Marsland et al 2015; Zheng et al 2016). Recent evidence suggests that an altered intestinal microbiota, a reduction of bacterial diversity or a shift in microbial composition, is associated with the development of hypersensitivity disorders in humans, but this is unknown for horses. Conclusion: Our observations suggest that hypersensitivity disorders in adult horses are not associated with an alteration of the intestinal microbiota, but environmental and/or location factors strongly influence these bacteria
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