April Case of the Month: Spring Vaccines and their Reactions

Lucy is an 8 year old warmblood mare who the owner recently purchased as a dressage prospect. Lucy came from a training barn in Alberta where she was vaccinated and dewormed last year. As Lucy’s owner prepared for the summer season, she wanted to ensure that Lucy was healthy and protected against infectious diseases and booked a wellness exam with Swiftsure Equine. At this exam, Lucy had a detailed physical examination, diet & weight analysis, and teeth check. She also had a fecal egg count and was found to have a low worm burden. We were happy to give Lucy a clean bill of health and discussed vaccinations with Lucy’s owner. A vaccine program was determined to best protect Lucy from the infectious diseases based on our geographic region, her risk of exposure, and the potential severity of diseases she may be exposed to. Lucy was vaccinated at the time of her appointment and risks of vaccine reaction were discussed with the owner. Over the next few days, Lucy’s owner noticed that she seemed quieter than usual and had some signs of inflammation at the site of vaccination. The owner checked in with the SEVS team and at our direction took her temperature which revealed a mild fever (>38.5C). Based on her signs it was determined that Lucy required some supportive care including elevating her feed & water, providing a soupy mash for extra hydration, and the veterinarian prescribed an anti-inflammatory. Within another 24 hours Lucy was back to her normal self with a good appetite.

This response seen by Lucy is not uncommon and part of the recognized signs we may see from horses following vaccination. Vaccines are designed to be highly effective at stimulating the immune system to protection against the diseases we vaccinate for. As a result of this stimulation, horses may experience mild and short-term effects including injection site inflammation, decreased appetite, fatigue, fever, and lack of energy. Horses that show these signs often recover quickly and without intervention. Many horses may display no signs at all. In rare cases, horses may experience an allergic reaction of more severe side effects following vaccination. In these cases, veterinary intervention is warranted. This would include if the signs are persisting for more than 48 hours, hives, colic, complete loss of appetite, difficulty breathing, or any other concerns are noted. Luckily, these events are rare and the benefits of vaccination in their protection against potentially fatal diseases such as tetanus strongly outweigh the risks in most cases. The Swiftsure team is here to help support you and your herd and help make evidence based decisions on which vaccine program is best for your horses and follow up with care in the case they feel a bit off after their vaccines.