Potomac Horse Fever Facts

Potomac Horse Fever Facts

Summertime, and the living is easy…for the carriers of Potomac Horse Fever (PHF). Our wet spring and recent hot weather provide favorable environments for the aquatic insects and snails that carry the bacteria and infect horses. Here are some key pieces of information about PHF that can help protect your horses:

What to look for: Common signs of horses with PHF include fever (up to 107° F), colic, diarrhea, poor appetite, laminitis (founder), depression/lethargy, swelling of the limbs and/or ventral abdomen, and pregnancy loss. A horse with PHF may show any, all, or a combination of these signs. Because prompt treatment increases the chance of successful treatment, call your veterinarian if you think your horse may have PHF.

Infection: Infection with PHF comes from contact with caddisflies, mayflies, dragonflies, damselflies, and some snails. Because horses become infected with PHF due to insects in the environment, multiple horses on a property may become infected. Although it is an infection, it is not contagious from one horse to another. However, because some contagious diseases show the same signs (fever, colic, diarrhea), it is prudent to keep any horse with these signs isolated from others until the cause of the illness can be determined. Also, some horses with PHF can have other intestinal diseases at the same time.

Treatment: Tetracycline antibiotics are used to kill the organism, and supportive care is often also needed to treat the colitis (intestinal inflammation) that results from infection. Colitis can be very serious, even fatal in horses, and treatment may be complicated and expensive. Laminitis may further complicate treatment and outcome.

Prevention: Horses most at risk are those housed within 5 miles of a stream or pond. Risk of infection can be decreased by vaccinating horses against PHF, and through some environmental management. The vaccine is not always successful at preventing infection, but horses that have been vaccinated generally experience a milder form of the disease if they do become ill. In some circumstances, it may be beneficial to booster the vaccine in late summer; a discussion with your veterinarian can help determine if this would be helpful. Because many of the insects that carry PHF are attracted to light, turning off the barn lights at night can help protect horses from becoming sick.

We have seen multiple cases of PHF in our hospital already this year, and if the hot, rainy weather continues, we are likely to have more cases. Please give our office a call if you have any questions about PHF.