Do Horses With Equine Metabolic Syndrome (EMS) Have Reduced Immune Responses to Vaccination?

More than 30% of the human population is considered to be obese [1]. Not only is this an increasing problem in humans, but in the horse population as well. Recent reports indicate the percentage of overweight horses may range anywhere from 20.6-41%. Obesity in horses has been connected to more serious health concerns of insulin resistance (IR) and equine metabolic syndrome (EMS). Horses of varying breeds, including Quarter Horses, are affected by EMS. EMS is defined by the following: regional (neck crest, rump, etc.) or general obesity, hyperinsulinemia or insulin resistance, and a history of or predisposition towards laminitis. Given the link of EMS to laminitis, this is a serious problem for the industry. Ongoing and past research has been focused on characterizing and understanding mechanisms responsible for EMS. However, little research has been conducted to determine the impact of EMS on routine healthcare of these horses, in particular how these horses respond to vaccination. It has been shown that obese humans and mice have decreased immune responses to vaccination. EMS may have similar effects on the vaccine responses of these types of horses. Moreover, EMS horses may be more susceptible to disease, as well as acting as unknown disease reservoirs. Therefore, we propose to investigate the impact of EMS on immune responses to routine vaccination. Twenty-four mixed sex and age matched adult (8-21 years old) horses; 12 EMS and 12 non-EMS, age-matched controls (8 vaccinate and 4 non-vaccinate in each group) of mixed and Quarter horse breeds will be used in this study. Vaccination (influenza or saline) will be administered on day 0 and peripheral blood samples taken on day 0 prior to vaccination and on days 7 and 14 post vaccination. This study will be the first to determine if horses with EMS have reduced immune responses to vaccination.