Overweight horses seem to be becoming more common. This is despite the fact that obesity is recognized as causing significant problems in horses. It is linked with Equine Metabolic Syndrome (EMS) and insulin resistance, often resulting in laminitis.
Obesity in humans has been reported to depress the response to vaccination. Does the same thing happen in horses? Researchers at the M.H. Gluck Equine Research Center, in the Department of Veterinary Science, University of Kentucky, Lexington, investigated.
Twenty-five adult horses of various breeds were enrolled in the study; 13 with EMS and 12 without. Four horses in each group were left unvaccinated as controls and received saline injections; the rest received two doses of a commercial equine influenza vaccine three weeks apart.
The research team took blood samples to assess the response to treatment. Antibody levels (hemagglutination inhibition (HI) titres and equine influenza specific IgGa, IgGb, and IgGT) were measured before and at weekly intervals after vaccination. Cell mediated immune (CMI) responses were assessed by real-time polymerase chain reaction (RT-PCR) on peripheral blood mononuclear cells (PBMCs).
They found that all horses receiving influenza vaccination responded with significant increases (P < 0.05) in HI titres, and IgGa and IgGb equine influenza specific antibodies compared to saline controls.
EMS had no significant effect on humoral immune responses to influenza vaccination as measured by HI titres or IgG antibody. There was, however, an effect on CMI responses. Influenza-vaccinated EMS horses had lower gene expression of IFN-γ (P = 0.02) and IL-2 (P = 0.01) compared to vaccinated non-EMS control horses.
The authors conclude that, while metabolic status does not influence humoral responses to an inactivated influenza vaccine in horses, horses with EMS appear to have a reduced CMI response to vaccination compared to metabolically normal, non-EMS control horses.
For more details, see:
Humoral and cell-mediated immune responses to influenza vaccination in equine metabolic syndrome (EMS) horses
Sarah Elzinga, Stephanie Reedy, Virginia D.Barker, Thomas M.Chambers, Amanda A.Adams
Veterinary Immunology and Immunopathology (2018) Vol199, Pages 32-38