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Randomised study of the immunomodulatory effects of azithromycin in severely asthmatic horses
  1. Sophie Mainguy-Seers1,
  2. Amandine Vargas1,
  3. Olivia Labrecque2,
  4. Christian Bédard3,
  5. Pierre Hélie3 and
  6. Jean-Pierre Lavoie1
  1. 1 Faculty of Veterinary Medicine, Department of Clinical Sciences, Université de Montréal, St-Hyacinthe, Quebec, Canada
  2. 2 Laboratoire d'epidemiosurveillance animale du Quebec, Saint-Hyacinthe, Quebec, Canada
  3. 3 Faculty of Veterinary Medicine, Department of Pathology and Microbiology, Université de Montréal, St-Hyacinthe, Quebec, Canada
  1. Correspondence to Dr Jean-Pierre Lavoie; Jean-pierre.lavoie{at}


Neutrophilic inflammation is believed to contribute to the airway obstruction and remodelling in equine asthma. Azithromycin, an antibiotic with immunomodulatory properties, reduces pulmonary neutrophilia and hyper-responsiveness in human asthmatics and decreases airway remodelling in rodent models of asthma. It was therefore hypothesised that azithromycin would improve lung function, mucus accumulation and central airway remodelling by decreasing luminal neutrophilia in severe equine asthma. The effects of a 10-day treatment with either azithromycin or ceftiofur, an antimicrobial without immune-modulating activity, were assessed using a blind, randomised, crossover design with six severe asthmatic horses in clinical exacerbation. Lung function, tracheal mucus accumulation, tracheal wash bacteriology, bronchial remodelling, airway neutrophilia and mRNA expression of proinflammatory cytokines (interleukin (IL)-8, IL-17A, IL-1β, tumour necrosis factor-α) in bronchoalveolar lavage fluid were evaluated. Azithromycin decreased the expression of IL-8 (P=0.03, one-tailed) and IL-1β (P=0.047, one-tailed) but failed to improve the other variables evaluated. Ceftiofur had no effect on any parameter. The reduction of neutrophilic chemoattractants (IL-8, IL-1β) justifies further efforts to investigate the effects of a prolonged treatment with macrolides on airway neutrophilia and remodelling. The lack of efficacy of ceftiofur suggests that severe equine asthma should not be treated with antibiotics at first-line therapy.

  • horses
  • respiratory disease
  • internal medicine
  • respiratory physiology
  • inflammation
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  • Funding This study was funded by the Equine Research Funds of the Université de Montréal, an unrestricted research grant of Zoetis, the Fonds du Centenaire of the Université de Montréal and the Canadian Institutes of Health Research (grant #PJT-148807).

  • Competing interests None declared.

  • Ethics approval All experimental procedures were performed in accordance with the Canadian Council on Animal Care guidelines and were approved by the Animal Care Committee of the Faculty of Veterinary Medicine of the Université de Montréal (Protocol # Rech-1801).

  • Provenance and peer review Not commissioned; externally peer reviewed.

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