TEVA recommends boosting Potomac Horse Fever (PHF) vaccine for all horses not having the vaccine within the last 3 months.

LEESBURG, VA - An increased number of cases are being reported by all regional equine veterinary practices. This sweltering hot and wet summer has led to an increase in aquatic insects which are the natural carriers of the PHF bacteria. Horses accidentally ingest the insect and the bacteria gets into the horse's system. It is not contagious between horses at any point, but it can be deadly. It is treatable with intravenous oxytetracycline.

For many horses, this vaccine booster means scheduling an early Fall visit; or you may elect for the PHF now, and then complete your remaining Fall vaccines at their usual time (possibly with another PHF vaccine or without the PHF vaccine depending your farm's location and water proximity/risks). In every case, this booster should not influence your usual Spring 2023 scheduling as PHF risk is small in the spring.

Vaccination either prevents or greatly reduces the severity of the disease (often the difference between life and death).

To schedule, call or text TEVA at 703-505-2320, or send an email to

For more information, look for PHF among the diseases at EDCC:

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