ABSTRACT
The objective of the present case-control study was to determine prevalence factors associated with the detection of equine herpesvirus type 1 (EHV-1) by quantitative PCR (qPCR) in horses presented to veterinarians with clinical signs related to an upper respiratory tract infection and/or acute onset of neurological disease from March 2008 to December 2014. Nasal secretions and whole blood from 4228 equids with acute onset of fever, respiratory signs and/or neurological deficits were tested by qPCR for EHV-1. Categorical analyses were performed to determine the association between observations and EHV-1. A total of 117/4228 (2.7 per cent) equids tested qPCR-positive for EHV-1, with most of the isolates belonging to the non-neuropathogenic genotype (N752). EHV-1 PCR-positive equids were over-represented in racing horses. Depression, anorexia, nasal discharge and coughing were significantly less frequently reported in the EHV-1 qPCR-positive equids compared with the EHV-1 qPCR-negative cases. Neurological deficits were more frequently reported in the EHV-1 qPCR-positive cases. This study provides contemporary information on the frequency of EHV-1 detection by qPCR in blood and nasal secretions from horses with fever, respiratory signs and neurological deficits.
Subject(s)
Herpesviridae Infections/veterinary , Herpesvirus 1, Equid/isolation & purification , Horse Diseases/virology , Nervous System Diseases/veterinary , Respiratory Tract Infections/veterinary , Acute Disease , Animals , Case-Control Studies , Herpesviridae Infections/epidemiology , Herpesviridae Infections/virology , Herpesvirus 1, Equid/genetics , Horse Diseases/epidemiology , Horses , Nervous System Diseases/epidemiology , Nervous System Diseases/virology , Prevalence , Real-Time Polymerase Chain Reaction/veterinary , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/virology , Risk FactorsABSTRACT
BACKGROUND: Recent surveillance studies for equine respiratory viruses have shown that equine influenza virus (EIV) continues to be a prevalent respiratory virus of equids throughout the United States and Europe. OBJECTIVES: To gain a better understanding of the prevalence and epidemiology of EIV shed by horses, mules and donkeys in the United States from March 2010 to November 2013. ANIMALS: 2,605 equids. METHODS: Nasal secretions from index cases with acute onset of respiratory disease were tested by qPCR for EIV. Multilevel logistic regression was used to model the association between EIV status and prevalence factors. Furthermore, observations from EIV-positive study horses were compared to previous data from March 2008 to February 2010. RESULTS: A total of 230 (9.7%) index cases tested qPCR positive for EIV. A higher-than-expected proportion of EIV qPCR-positive horses occurred in the 1-5, 6-10, and 11-15 age groups when compared to the <1 year of age group. Fever, nasal discharge and coughing were positively associated with EIV-positive horses. EIV qPCR-positive study cases were significantly older and more often vaccinated against EIV compared to EIV qPCR-positive animals from the 2008-2010 study period. CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides valuable and contemporary information on the frequency of EIV detected by qPCR in the United States. The results also underscore that older and previously vaccinated horses were susceptible to EIV.
