Q: My filly picked up a fever while at the trainer’s getting started under saddle (bloodwork indicated an infection, which my vet said probably caused by a virus). She then went off feed for nearly four days, so I brought her home to rest and recoup. While we didn’t scope her to verify the diagnosis, my vet suspected she had gastric ulcers after the combination of not eating and receiving Banamine paste (flunixin meglumine, a non-steroidal anti-inflammatory drug, or NSAID) for the fever. A course of GastroGard (prescription-strength omeprazole used to treat ulcers, rather than prevent them) helped—she started eating again almost immediately after the first dose. I’m now worried about sending her back into training. Is it likely she will suffer gastric ulcers again when put under the stress of moving to the barn and training? If so, is there any way to prevent ulcer onset?

—A.G., Oregon

A: Your veterinarian is right! The initial onset of fever and loss of appetite at the trainer’s barn was likely due to a viral infection, such as equine influenza (often called flu), equine herpesvirus-1 (EHV-1), or equine rhinitis virus.   These viruses usually cause a fever and variable cough, nasal discharge, and loss of appetite, but in some cases horses show very mild signs.

Gastric ulcers can be a primary disease or can occur secondary to another disease or stressor, such as flu, fever, being off-feed, phenylbutazone (Bute, another NSAID) or Banamine administration, painful musculoskeletal injury, colic, etc.).   It sounds like your horse might have had ulcers secondary to the combination of fever, loss of appetite, and NSAID treatment, and that omeprazole was effective. Also, whatever caused her fever and loss of appetite (probably a virus) ran its course, and the horse improved from infection