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J Vet Intern Med. 2008 Sep-Oct;22(5):1234-8. doi: 10.1111/j.1939-1676.2008.0172.x. Epub 2008 Aug 6.

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

Author information

1
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. gap7@cornell.edu

Abstract

BACKGROUND:

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.

OBJECTIVES:

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.

ANIMALS:

Fifteen horses experimentally infected with EHV-1.

METHODS:

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.

RESULTS:

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).

CONCLUSIONS AND CLINICAL IMPORTANCE:

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.

PMID:
18691363
DOI:
10.1111/j.1939-1676.2008.0172.x
[Indexed for MEDLINE]
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