Investigation of the Molecular Detection of Vaccine-derived Equine Herpesvirus Type 1 in Blood and Nasal Secretions from Horses Following Intramuscular Vaccination

• Published in: Journal of veterinary diagnostic investigation 2007-05, Vol.19 (3), p.290-293
• Main Authors: Pusterla, N, Chaney, K.P, Maes, R, Wise, A.G, Holland, R, Schott, H.C. II
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Viral - blood; blood; bodily secretions and exudates; disease detection; disease transmission; DNA, Viral - chemistry; DNA, Viral - genetics; Equine Herpesvirus Type 1; Female; Herpesviridae; Herpesviridae Infections - blood; Herpesviridae Infections - veterinary; Herpesviridae Infections - virology; Herpesvirus 1, Equid - genetics; Herpesvirus 1, Equid - immunology; Herpesvirus Vaccines - blood; Herpesvirus Vaccines - immunology; horse diseases; Horse Diseases - prevention & control; Horse Diseases - virology; Horses; Injections, Intramuscular; intramuscular injection; Male; nasal mucosa; Nasal Mucosa - metabolism; Nasal Mucosa - virology; Neutralization Tests - veterinary; Pilot Projects; polymerase chain reaction; Polymerase Chain Reaction - veterinary; Random Allocation; vaccination; Vaccination - veterinary; vaccines; Vaccines, Attenuated - immunology
• ISSN: 1040-6387; 1943-4936
• DOI: 10.1177/104063870701900311

Correspondence: 1 Corresponding Author: Nicola Pusterla, Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, One Shields Avenue, Davis, CA 95616 The objective of this study was to investigate whether intramuscular vaccination of healthy adult horses with a killed or a modified live equine herpesvirus type 1 (EHV-1) vaccine could induce transient positive PCR results in either blood or secretions collected on a nasopharyngeal swab. Four horses in each group received either a single killed or a modified-live vaccine intramuscularly. Two local commingled and 2 distant nonvaccinated controls were included for each group. All horses were observed daily for evidence of clinical abnormalities throughout the study periods. Blood and nasopharyngeal swabs were collected twice before vaccination and once weekly for 4 weeks after vaccination and submitted for PCR testing for EHV-1 by 2 independent laboratories using different real-time PCR methodologies. Serum samples collected from all horses on the vaccination day and 21 days later were tested for antibodies against EHV-1 using a serum neutralization test. Whereas the 2 vaccine strains tested positive in both EHV-1 PCR assays, nasopharyngeal swabs and whole blood collected from vaccinated and control horses had negative PCR test results for EHV-1 during the entire study period. Serum neutralization testing revealed a 2- to 4-fold increase in titers for all vaccinated horses, whereas titers in control horses were largely unchanged. The use of seropositive horses before immunization and the sampling frequency of 7 days may have prevented the occasional molecular detection of the vaccine virus in whole blood and nasopharyngeal secretions. However, the study results demonstrate that detection of EHV-1 DNA by PCR in vaccinated and unvaccinated healthy horses is not a common event. Key Words: EHV-1 • healthy horses • PCR detection • vaccine