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


OBJECTIVE
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.


METHODS
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
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.
Perkins
G A
GA
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. gap7@cornell.edu
Goodman
L B
LB
Dubovi
E J
EJ
Kim
S G
SG
Osterrieder
N
N
D000818:Animals; D006566:Herpesviridae Infections / Q000662:veterinary* / Q000821:virology; D004861:Herpesvirus 1, Equid / Q000302:isolation & purification*; D006734:Horse Diseases / Q000821:virology*; D006736:Horses; D009666:Nose / Q000821:virology*; D016133:Polymerase Chain Reaction / Q000379:methods / Q000662:veterinary*; D012680:Sensitivity and Specificity; D013997:Time Factors; D017201:Virus Shedding