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.

中文翻译：

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过敏性疾病和环境因素对马肠道菌群的影响。

背景：最近的证据表明，肠道菌群的改变，特别是细菌多样性的降低或微生物组成的改变，与人类超敏性疾病的发展有关，但这对马来说尚不明确。受库里科尼德超敏反应或严重马哮喘或两者影响的马的肠道菌群多样性降低。我们还调查了环境影响。方法：收集了总共140匹马的直肠拭子样本，并且主人完成了有关它们的马的详细调查表。对于每只过敏马，均从相同的马stable中抽取一个健康的同龄动物作为环境匹配的对照。通过评估细菌16S rRNA基因的V4区来确定拭子中的微生物群。通过α和β多样性指数调查细菌群落的结构。结果：健康马和过敏马之间的分组比较未显示出α（p = 0.9）和β多样性（p = 0.5）的显着差异。但是，微生物的结构与环境因素有关，例如稳定的类型（p = 0.001），可进入牧场（p = 0.001）或喂养的类型（p = 0.003）。结论：我们的观察结果表明，成年马的超敏性疾病与肠道菌群的改变无关，而与环境和环境有关。 /或位置因素强烈影响这些细菌。