Abstract: Background – Equine herpesvirus type-1 (EHV-1) infects through the epithelium of the upper respiratory tract (URT). Mucosal antibodies (mucAbs) against EHV-1 were shown previously to correlate with protection from disease. EHV vaccination is typically performed intramuscularly (i.m.). Transfer of systemic vaccine antibodies to the URT has not been shown.Hypothesis/Objectives – The hypotheses were (i) intramuscular vaccination will result in both systemic and mucAbs, and (ii) frequent vaccination will not increase antibodies beyond certain concentrations. The objective was to provide information on systemic and mucAb responses after frequent vaccination of horses with prior EHV vaccination and/or infection history. Animals – Fourteen Icelandic research horses, 5-13 years-old, ten mares, five geldings. All horses had existing EHV-1 antibodies prior to this vaccination study and thus resemble adult client horses with EHV vaccination history.Methods – Descriptive longitudinal vaccination study, Calvenza EHV(R) i.m. on days 0, 22 and 2, 3, 6 and 8 months. Serum and nasal swab samples were collected at different times post vaccination and used for antibody detection in a new sensitive EHV-1 Risk Evaluation assay. EHV-1 specific antibody responses were compared pre- and post-vaccination by Friedman tests with Dunn’s post-tests.Results – EHV-1 specific serum antibodies plateaued after the second and subsequent vaccinations. MucAbs significantly increased beyond pre-vaccination levels after the fourth vaccination and consisted mostly of IgG4/7.Conclusions/clinical importance – Intramuscular vaccination resulted in increasing mucAbs at the URT which likely can neutralize EHV, thereby preventing disease. Frequent vaccination increased mucAbs while serum antibodies were less affected.
