title: Association between inflammatory airway disease of horses and exposure to respiratory viruses: a case control study.
abstract: BACKGROUND
  Inflammatory airway disease (IAD) in horses, similar to asthma in humans, is a common cause of chronic poor respiratory health and exercise intolerance due to airway inflammation and exaggerated airway constrictive responses. Human rhinovirus is an important trigger for the development of asthma; a similar role for viral respiratory disease in equine IAD has not been established yet.
  
  
  METHODS
  In a case-control study, horses with IAD (n = 24) were compared to control animals from comparable stabling environments (n = 14). Horses were classified using pulmonary function testing and bronchoalveolar lavage. PCR for equine rhinitis virus A and B (ERAV, ERBV), influenza virus (EIV), and herpesviruses 2, 4, and 5 (EHV-2, EHV-4, EHV-5) was performed on nasal swab, buffy coat from whole blood, and cells from BAL fluid (BALF), and serology were performed. Categorical variables were compared between IAD and control using Fisher's exact test; continuous variables were compared with an independent t-test. For all analyses, a value of P <0.05 was considered significant.
  
  
  RESULTS
  There was a significant association between diagnosis of IAD and history of cough (P = 0.001) and exercise intolerance (P = 0.003) but not between nasal discharge and IAD. Horses with IAD were significantly more likely to have a positive titer to ERAV (68 %) vs. control horses (32 %). Horses with IAD had higher log-transformed titers to ERAV than did controls (2.28 ± 0.18 v.1.50 ± 0.25, P = 0.038). There was a significant association between nasal shedding (positive PCR) of EHV-2 and diagnosis of IAD (P = 0.002).
  
  
  CONCLUSIONS
  IAD remains a persistent problem in the equine population and has strong similarities to the human disease, asthma, for which viral infection is an important trigger. The association between viral respiratory infection and development or exacerbation of IAD in this study suggests that viral infection may contribute to IAD susceptibility; there is, therefore, merit in further investigation into the relationship between respiratory virus exposure and development of IAD.
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Houtsma
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Daniela
authors.initials: D
authors.lastname: Bedenice
authors.affiliation: University of California, Davis, Davis, CA USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Pusterla
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Brenna
authors.initials: B
authors.lastname: Pugliese
authors.affiliation: University of California, Davis, Davis, CA USA.
authors.forename: Samantha
authors.initials: S
authors.lastname: Mapes
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Hoffman
authors.affiliation: The College of the Holy Cross, Worcester, USA.
authors.forename: Julia
authors.initials: J
authors.lastname: Paxson
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Rozanski
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Jean
authors.initials: J
authors.lastname: Mukherjee
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Margaret
authors.initials: M
authors.lastname: Wigley
authors.affiliation: Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA USA.
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Mazan
keywords: Asthma; Bronchoalveolar lavage; Equine herpesvirus-2; Equine rhinitis virus; Pulmonary function testing