Association between inflammatory airway disease of horses and exposure to respiratory viruses: a case control study

Ashley Houtsma; Daniela Bedenice; Nicola Pusterla; Brenna Pugliese; Samantha Mapes; Andrew M. Hoffman; Julia Paxson; Elizabeth Rozanski; Jean Mukherjee; Margaret Wigley; Melissa R. Mazan

doi:10.4081/mrm.2015.332

Association between inflammatory airway disease of horses and exposure to respiratory viruses: a case control study

Authors

Ashley Houtsma Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Daniela Bedenice Cummings School of Veterinary Medicine, Tufts University, North Grafton,
Nicola Pusterla University of California, Davis, Davis, CA
Brenna Pugliese Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Samantha Mapes University of California, Davis, Davis, CA, USA.; The College of the Holy Cross, Worcester
Andrew M. Hoffman Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Julia Paxson The College of the Holy Cross, Worcester
Elizabeth Rozanski Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Jean Mukherjee Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Margaret Wigley Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA
Melissa R. Mazan Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA

DOI: https://doi.org/10.4081/mrm.2015.332

Keywords:

Asthma, Bronchoalveolar lavage, Equine rhinitis virus, Equine herpesvirus-2, Pulmonary function testing

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.