Article

Detection of equine herpesvirus-1 in nasal swabs of horses by quantitative real-time PCR.

Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Journal of Veterinary Internal Medicine (impact factor: 1.99). 08/2008; 22(5):1234-8. DOI:10.1111/j.1939-1676.2008.0172.x
Source: PubMed

ABSTRACT Early identification of inhalation-transmitted equine herpesvirus type 1 (EHV-1) infections has been facilitated by the availability of a number of real-time quantitative PCR (qPCR) tests. A direct comparison between nasal swab qPCR and traditional virus isolation (VI) requires a method for normalizing the qPCR samples and controlling for PCR inhibitors present in some clinical samples.
To quantify EHV-1 shedding in viral swabs using an internal control and to compare fast qPCR to VI for the detection of EHV-1 in nasal swabs from horses.
Fifteen horses experimentally infected with EHV-1.
Experimental study: Nasal swab samples were collected daily after experimental infection for up to 21 days. VI was performed by conventional methods. The DNA was prepared for qPCR with the addition of a known quantity DNA of Marek's disease virus as an internal control. qPCR was performed.
The qPCR method detected virus up to day 21 after challenge, whereas VI detected virus only to day 5. The median Kaplan-Meier estimates for EHV-1 detection were 12 days for qPCR and 2 days for VI (P< .0001). When compared with VI, the sensitivity and specificity of qPCR were 97 (95% CI: 86-100) and 27% (95% CI: 20-35).
We conclude that fast qPCR of nasal swab samples should be chosen for diagnosis and monitoring of herpesvirus-induced disease in horses. Recommended reference ranges of C(T) values are provided as well as justification of a minimum 10-day quarantine period.

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Keywords

conventional methods
 
experimental infection
 
Experimental study
 
fast qPCR
 
herpesvirus-induced disease
 
inhalation-transmitted equine herpesvirus type 1
 
known quantity DNA
 
Marek's disease virus
 
median Kaplan-Meier estimates
 
minimum 10-day
 
nasal swab qPCR
 
Nasal swab samples
 
nasal swabs
 
PCR inhibitors present
 
qPCR method
 
qPCR samples
 
real-time quantitative PCR
 
Recommended reference ranges
 
traditional virus isolation
 
viral swabs
 

Nikolaus Osterrieder