Prevention of respiratory infections with alpha- and gamma-herpesviruses in weanling foals by using a modified live intra-nasal equine influenza vaccine.

Abstract

This study aimed to determine if the administration of a modified live equine influenza virus vaccine (FluAvert) to foals would positively impact their health and reduce colonization of their upper airways with equine herpesviruses (EHV) during the weaning period. A single dose of FluAvert was given to 20 healthy foals 7 days prior to being weaned; 20 healthy foals served as unvaccinated controls. Nasal secretions and blood were collected before vaccination, the day of weaning, and weekly thereafter for 3 weeks. Nasal secretions were tested by quantitative polymerase chain reaction (qPCR) for EHV-1, -2, -4 and -5. Whole blood was analyzed for a complete blood cell count and fibrinogen concentration. Physical assessments were made daily. The use of FluAvert was associated with a better clinical outcome. However, the equine influenza virus (EIV) vaccine did not influence selected hematological parameters and kinetics of herpesviruses. The clinical benefit observed in vaccinates may explain the perception that the EIV vaccine induces cross-protection against respiratory agents.