Horse Illustrated Magazine

The Virginia-Maryland Regional College of Veterinary Medicine (VMRCVM) issued an alert earlier this week to inform area horse owners of several cases of Potomac Horse Fever (PHF). The disease was originally discovered near the Potomac River in Maryland, but is now found throughout North America.

Symptoms of PHF include fever, diarrhea, laminitis, decreased abdominal sounds and mild colic. In rare cases, fetal infection can cause abortion in pregnant mares that contract the disease. Infection is rare in foals.

The statement from the VMRCVM explains that PHF is spread through a common parasite known as the freshwater fluke. In its developmental phase, the fluke infects aquatic snails and insets such as dragonflies and mayflies. The infection can spread to horses when they ingest infected snails, snail slime or insects while grazing or drinking. Rainy weather in the mid-Atlantic region this year may have led to more infected snails and insects reaching horse farms, causing the recent cases.

The disease is not contagious from one horse to another, but if one horse is infected, it’s important to take precautions to protect other horses on the farm.

Vaccines are available to protect against PHF, but according to the American Association of Equine Practitioners, there are questions about the effectiveness of those vaccines. Horse owners are encouraged to talk to their veterinarians about whether or not using a PHF vaccine is warranted for their horse. Preventive management strategies include turning stable lights off at night to avoid attracting insects and frequently scrubbing water buckets and outdoor troughs to prevent them from becoming breeding grounds for bugs.