Innate and specific immune responses to intranasal modified-live EHV-1 virus vaccination in previously immunised equids - a pilot

Abstract

Previous studies investigating the potential involvement of viruses in airway inflammation were based either on serological tests or on PCR from nasal swabs only. The objectives of this study were to determine the incidence of welland less-characterised viruses in the equine airways, and their association with clinical signs. In a 2-year prospective longitudinal study, nasal swabs (NS) and tracheal washes (TW) were collected monthly on 52 Standardbred racehorses at training (581 samples). Equine aand g-herpesviruses, equine rhinitis virus-A and -B, equine adenovirus-A, and equine influenza virus were investigated by qPCR. Any positive sample was subcategorised as non-quantifiable (>LOD and LOQ). Clinical signs (nasal discharge, coughing), and tracheal mucus score were simultaneously recorded. In TW, respective monthly incidences were 27.9% (EHV-5), 24.8% (EHV-2), 7.1% (ERBV), 3.8% (EHV-4), 1.9% (EAdV1) and 0.2% (EHV-1, ERAV). EIV has not been detected in any sample. Molecular detection of EHV-2 and ERBV in TW were significantly associated with coughing (OR 3.1; 95% CI 1.4-7.1; P1⁄40.01 and OR 5.3; 95% CI 2.1-14.0; P<0.001, respectively). Positive samples for EHV-2 in TW were significantly associated with tracheal mucus score 2 (OR 2.1; 95% CI 1.2-3.8; P1⁄40.02). When based on quantifiable detection, ERBV only was significantly associated with coughing (OR 15.0; 95% CI 3.7-60.0; P<0.001). Positive samples for any virus in NS were not associated with clinical signs. Based on our data, detecting ERBV in TW is a major risk-factor of coughing. This virus should be considered when investigating horses with inflammatory airway disease.