Airway inflammation in Michigan pleasure horses: prevalence and risk factors.
Abstract: Although subclinical airway inflammation is thought to be common in horses, there is little information on its prevalence and none on risk factors. Objective: To determine the prevalence and risk factors for an increased number of inflammatory cells and for mucus accumulation in the trachea of pleasure horses. Methods: Horses (n = 266) in stables (n = 21) in Michigan were examined endoscopically, once in winter and once in summer 2004. Visible tracheal mucoid secretions were graded 0-5 and inflammatory cell numbers counted in a tracheal lavage sample. Information collected about each horse included age, gender, presence of cough, percent time indoors and source of roughage. The repeated measures were analysed by generalised estimating equations and linear mixed models. Results: Horses eating hay, especially from round bales, had the most neutrophils, whereas horses feeding from pasture had the fewest. Being female and being outdoors in winter were associated with increased numbers of inflammatory cells. Older horses had fewer macrophages than young horses. More than 70% of horses had >20% neutrophils in tracheal lavage. Twenty percent of horses had a mucus accumulation score >1; 17% had both a mucus score >1 and >20% neutrophils. The significant risk factors for mucus accumulation >1 were age >15 years, feeding on hay as compared to pasture, and being outdoors for more than 80% time in winter. Even though mucus accumulation score >1 was a risk factor for cough, only half of such horses coughed. Cough and mucus accumulation were associated with increased number of neutrophils. Conclusions: In comparison to pasture feeding, hay feeding, particularly from round bales, was associated with an increased number of neutrophils in the airway. Being outdoors in winter was associated with increased numbers of inflammatory cells and with mucus accumulation. Because 70% of horses have >20% neutrophils, this value should not be used as the sole indicator of airway inflammation. Conclusions: The study reinforces the importance of hay feeding and older age as risk factors for inflammatory airway disease. Horses that do not have 'heaves' may be best kept indoors when winters are cold.
Publication Date: 2006-07-27 PubMed ID: 16866194DOI: 10.2746/042516406777749281Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article presents findings on the prevalence of airway inflammation in leisure horses in Michigan and explores the possible risk factors that contribute to such conditions. Specifically, the horses’ diet, surrounding conditions, age, and gender are investigated for their potential implications on having inflammation and mucus accumulation in the tracheal area.
Methodology and Data Collection
- The researchers conducted endoscopic exams on 266 horses in 21 stables in Michigan across both winter and summer seasons of 2004.
- Tracheal mucoid secretions were noted on a scale of 0 to 5 and inflammatory cell numbers were counted from a tracheal lavage sample.
- Apart from these physical observations, other information such as the horse’s age, gender, presence of a cough, the time spent indoors, and the source of roughage in their diet was recorded for each horse.
Results
- Feeding hay, particularly from round bales, was associated with a greater number of neutrophils in the horses’ airway, as opposed to those who fed on pasture.
- Females and horses which stayed outdoors in winter showed a rise in the number of inflammatory cells.
- Older horses showed fewer macrophages compared to young ones.
- Over 70% of horses presented with more than 20% neutrophils in their tracheal lavage.
- Mucus accumulation was noted in 20% of horses, with 17% also exceeding the 20% neutrophil count.
- Risk factors for significant mucus accumulation were identified as older age (above 15 years), feeding on hay (especially when compared to pasture), and spending more than 80% of their time outdoors in winter.
- While mucus accumulation and coughing were associated with increased neutrophil numbers, only half of the horses with mucus score above 1 demonstrated a cough.
Conclusions
- Horses feeding on hay, particularly from round bales, and those that spent a majority of their time outdoors in winter showed a high number of neutrophils in their airways. Because a large proportion (70%) of horses demonstrated a neutrophil percentage above 20%, this statistic should not be the only indicator of airway inflammation.
- The findings also underscored the significance of hay feeding and older age as major risk factors for inflammatory airway disease in horses.
- The study recommends that horses not suffering from ‘heaves’ might fare better when kept indoors during severe winters.
Cite This Article
APA
Robinson NE, Karmaus W, Holcombe SJ, Carr EA, Derksen FJ.
(2006).
Airway inflammation in Michigan pleasure horses: prevalence and risk factors.
Equine Vet J, 38(4), 293-299.
https://doi.org/10.2746/042516406777749281 Publication
Researcher Affiliations
- Department of Large Animal Clinical Sciences, Michigan State University, East Lansing 48824-1314, USA.
MeSH Terms
- Age Factors
- Analysis of Variance
- Animal Feed / adverse effects
- Animals
- Bronchoalveolar Lavage Fluid / cytology
- Female
- Horse Diseases / epidemiology
- Horse Diseases / pathology
- Horses
- Housing, Animal
- Inflammation / epidemiology
- Inflammation / pathology
- Inflammation / veterinary
- Linear Models
- Male
- Michigan / epidemiology
- Mucus / metabolism
- Neutrophils / immunology
- Prevalence
- Respiratory Tract Diseases / epidemiology
- Respiratory Tract Diseases / pathology
- Respiratory Tract Diseases / veterinary
- Risk Factors
- Seasons
- Sex Factors
Citations
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