Association between equine asthma and fungal elements in the tracheal wash: An environment-matched case-control study.
Abstract: The presence of fungi in tracheal wash (TW) of horses was recently linked to mild-moderate equine asthma, indicating a possible causal role; however, increased numbers of fungi may also stem from asthma-related alteration of tracheal mucus clearance or from environmental exposure. Our objective was to elucidate the association between the presence of fungi in TW and asthma status while controlling for relevant confounders. We conducted a retrospective case-control study involving 73 horses, including 34 controls and 39 asthmatic cases. Each asthmatic horse was matched with a control from the same barn to account for the influence of environmental exposure. All horses underwent respiratory clinical scoring, endoscopy, TW, and bronchoalveolar lavage (BAL). The association between asthma status and presence of TW fungi was tested with multivariable logistic regression modelling, accounting for selected management factors, tracheal mucus accumulation, and selected TW and BAL cytological characteristics, including multinucleated giant cells (MGCs) in the TW. Given the variability in MGC definitions in the literature, particularly concerning their morphology and number of nuclei, we constructed two distinct models for each outcome (asthma status or presence of fungi in TW): one considering MGCs as cells with ≥ 3 nuclei, and another using a criterion of ≥ 10 nuclei. Horses with a tracheal mucus score ≥ 2 exhibited 3.6 to 4.3 higher odds of being asthmatic, depending on the MGC definition. None of the other variables examined were associated with either asthma status or TW fungi detection. Notably, the presence of fungal elements in the TW was not associated with equine asthma.
Copyright: © 2024 Dély et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Publication Date: 2024-09-06 PubMed ID: 39240830PubMed Central: PMC11379288DOI: 10.1371/journal.pone.0309835Google Scholar: Lookup
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Summary
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This research study examined whether there is a link between the presence of fungi in a horse’s tracheal wash (a respiratory diagnostic procedure) and equine asthma. The study didn’t find an association, suggesting that while fungi can be present in the tracheas of both asthmatic and healthy horses, it does not necessarily cause asthma in horses.
Study Design and Methodology
- The study was a retrospective case-control design involving a sample of 73 horses. This type of study involves looking back at existing health records and other data to compare a group of horses with asthma (39 horses, the “cases”) to a group of healthy horses (34 horses, the “controls”).
- Each horse with asthma was matched with a healthy horse from the same barn to control for environmental factors, like the exposure to the same outdoor and indoor environments.
- All the horses involved in the study had health assessments such as clinical scoring of respiratory issues, endoscopy, tracheal wash, and bronchoalveolar lavage (BAL) – a procedure in which a bronchoscope is passed through the mouth or nose into the lungs, fluid is squirted into a small part of the lung, and then collected for examination.
Statistical Analysis
- In order to understand the relationship between the presence of fungi in the tracheal wash and asthma, a multivariable logistic regression model was used. This statistical method allows for interpretation of the contribution of various factors in predicting a particular outcome.
- The model considered management factors like stable conditions, humidity levels, and feed types, as well as specific clinical characteristics such as the presence of multinucleated giant cells (MGCs) in the tracheal wash – large cells that contain multiple nuclei and are often indicative of an inflammatory response.
- Two separate models were developed depending on the defined properties of the MGCs – one with a criterion of 3 or more nuclei, and another with a criterion of 10 or more nuclei.
Key Findings
- Horses that had higher scores for tracheal mucus accumulation (2 or more) had significantly higher odds (3.6 to 4.3 times higher) of having asthma. The odds varied depending on the definition used for MGCs.
- None of the other factors considered in the study – including the presence of fungi in the tracheal wash – were shown to be related to the development of asthma in horses.
- The main conclusion is therefore that, while equine asthma may cause an increased accumulation of mucus in the trachea, the detection of fungal elements in the trachea is not associated with the disease.
Cite This Article
APA
Dély S, Gerber V, Peters LM, Sage SE.
(2024).
Association between equine asthma and fungal elements in the tracheal wash: An environment-matched case-control study.
PLoS One, 19(9), e0309835.
https://doi.org/10.1371/journal.pone.0309835 Publication
Researcher Affiliations
- Vetsuisse Faculty, Department of Clinical Veterinary Medicine, Swiss Institute of Equine Medicine (ISME), University of Bern, Bern, Switzerland.
- Vetsuisse Faculty, Department of Clinical Veterinary Medicine, Swiss Institute of Equine Medicine (ISME), University of Bern, Bern, Switzerland.
- Vetsuisse Faculty, Department of Clinical Veterinary Medicine, Clinical Diagnostic Laboratory, University of Bern, Bern, Switzerland.
- Vetsuisse Faculty, Department of Clinical Veterinary Medicine, Swiss Institute of Equine Medicine (ISME), University of Bern, Bern, Switzerland.
MeSH Terms
- Animals
- Horses / microbiology
- Asthma / microbiology
- Trachea / microbiology
- Case-Control Studies
- Horse Diseases / microbiology
- Fungi / isolation & purification
- Retrospective Studies
- Male
- Female
- Bronchoalveolar Lavage Fluid / microbiology
Conflict of Interest Statement
The authors have declared that no competing interests exist.
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