Frequency of shedding of respiratory pathogens in horses recently imported to the United States

Abstract

BackgroundImported horses that have undergone recent long distance transport might represent a serious risk for spreading infectious respiratory pathogens into populations of horses.ObjectiveTo investigate the frequency of shedding of respiratory pathogens in recently imported horses.AnimalsAll imported horses with signed owner consent (n = 167) entering a USDA quarantine for contagious equine metritis from October 2014 to June 2016 were enrolled in the study.MethodsProspective observational study. Enrolled horses had a physical examination performed and nasal secretions collected at the time of entry and subsequently if any horse developed signs of respiratory disease during quarantine. Samples were assayed for equine influenza virus (EIV), equine herpesvirus type‐1, −2, −4, and −5 (EHV‐1, −2, −4, −5), equine rhinitis virus A (ERAV), and B (ERBV) and Streptococcus equi subspecies equi (S. equi) using quantitative PCR (qPCR).ResultsEquine herpesviruses were detected by qPCR in 52% of the study horses including EHV‐2 (28.7%), EHV‐5 (40.7%), EHV‐1 (1.2%), and EHV‐4 (3.0%). Clinical signs were not correlated with being qPCR‐positive for EHV‐4, EHV‐2, or EHV‐5. None of the samples were qPCR‐positive for EIV, ERAV, ERBV, and S. equi. The qPCR assay failed quality control for RNA viruses in 25% (46/167) of samples.Conclusions and Clinical ImportanceClinical signs of respiratory disease were poorly correlated with qPCR positive status for EHV‐2, −4, and −5. The importance of γ‐herpesviruses (EHV‐2 and 5) in respiratory disease is poorly understood. Equine herpesvirus type‐1 or 4 (EHV‐1 or EHV‐4) were detected in 4.2% of horses, which could have serious consequences if shedding animals entered a population of susceptible horses. Biosecurity measures are important when introducing recently imported horses into resident US populations of horses.

What have we learned from 7 years of equine rhinitis B virus qPCR testing in nasal secretions from horses with respiratory signs

“…Further, the clinical role of ERBV is supported by the difference in detection rates between horses with respiratory signs (5.1%) and healthy controls (0.8%). These data are also supported by a recent study showing no ERBV detection by qPCR in 167 recently imported, healthy horses 18 . In comparison to ERBV, only four single nasal swabs tested qPCR‐positive for ERAV, a likely reflection of the study population tested (i.e.…”

Detection of Equid gammaherpesvirus 2 and 5 DNA in the upper respiratory tract of asymptomatic horses from Southern Brazil

“…These findings and results from previous studies [3,15,22,23] indicate that EHV-2 is more frequently correlated with equine respiratory disease when compared with EHV-5, which is more frequently detected in asymptomatic animals. The detection of both EHV-2 and EHV-5 from nasal swabs of the same horses has also been reported in animals from Switzerland and the USA [23,24]. Although the pathogenicity of gammaherpesviruses in horses is not fully elucidated, infections by these viruses are important predisposing factors for respiratory disease complexes in horses [25].…”

Molecular Detection of Equid Herpesvirus Type 2 (Ehv-2) and Type 5 (Ehv-5) in Bronchoalveolar Lavage Fluid From Asymptomatic Thoroughbred Horses in Southern Brazil

“…To our knowledge, the sensitivity for each sample type has not been determined to date. Moreover, the higher gammaherpesvirus incidence in comparison with alphaherpesvirus found by us and others (17,23,25) is likely due to the unavailability of vaccines for EHV-2 and -5, although experimental immunization of foals against EHV-2 has been reported (26).…”

“…A recent study analyzed the same infectious agents evaluated herein in animals imported into the United States. In 167 animals assessed using PCR from nasal swabs during 20 months, 48 were positive for EHV-2, 68 for EHV-5, and in 27 were double-positive for gammaherpesvirus, in which 72 were asymptomatic and 44 had various symptoms (e.g., fever, tachypnea, cough, lymphadenopathy, and nasal discharge)(17). It emphasizes the frequent and silent presence of gammaherpesvirus in equine populations.…”