08/18/2026
Potomac Horse Fever Season Is Here
The Miami Valley sees numerous cases of Potomac Horse Fever (PHF) every year, which is why we have always recommended PHF vaccination for every horse as part of their complete, comprehensive preventative care.
We typically see PHF from mid-summer through mid-fall, but our first case this year was diagnosed—and hospitalized—a few months ago. Thankfully, he responded well to treatment, made a full recovery, and was able to return home.
🐌 What is PHF?
PHF is caused by Neorickettsia risticii and is not spread horse-to-horse. Horses become infected by accidentally ingesting infected aquatic insects, such as caddisflies and mayflies. These insects are associated with freshwater and can also be attracted to barn lights.
🐌 Watch for:
Fever • Lethargy • Loss of appetite • Diarrhea • Colic • Laminitis
PHF can also cause abortion in pregnant mares. Early treatment is critical, and unfortunately, PHF can be fatal.
💉 What about vaccination?
The vaccine isn’t 100% effective at preventing PHF, but it can decrease the severity of illness and increase the chance of survival.
💡 Around the barn: Keep lights away from feed and water sources when possible, since lights attract the insects that can transmit PHF, and always provide clean, fresh drinking water.
If your horse received their last PHF vaccine 3 months ago or longer, now is a great time to schedule their booster. Give Gem City Equine a call with questions or to get your horse protected!
