Positive Cases of Potomac Horse Fever (PHF) in New Jersey
Six New Jersey Horses Have Died
Six horses in New Jersey have now died from Potomac Horse Fever. The first was from Mercer County near the Princeton area and the was from northern New Jersey. Both died within the last 10 days. Testing was confirmed by the New Jersey Animal Health Diagnostic Laboratory in Trenton, NJ. Please be aware that this disease is currently active in our practice area and take steps to protect your horse. Our condolences go out to these owners.
Herd of horses running along a green meadow under a rainbow against a stormy sky
What Is Potomac Horse Fever (PHF)?
Potomac Horse Fever (PHF) is caused by a bacteria called Neorickestia risticii. This bacteria is spread by flies, snails, and their flatworm parasites. Exactly how the disease is transmitted is not clear, but it may be from fly bites or consuming water containing infected snails or flatworms.

Potomac Horse Fever causes a high fever that comes in two waves. The first wave may go unnoticed because it is usually not accompanied by any other signs. The second fever arrives a few days later, usually accompanied by severe diarrhea, depression, and mild colic. The horse may also develop severe laminitis. Pregnant mares that become infected with PHF often abort their pregnancies several months after the infection. PHF is fatal in up to 30% of adult cases due to sepsis, dehydration, or incurable laminitis. If caught with the first fever, PHF can be treated with a short course of antibiotics. However, once the second fever and diarrhea has begun, the prognosis is much more grim.
Protecting your Horse from PHF
There are a number of ways to protect your horse from Potomac Horse Fever.
  1. The most effective method is to check your horse's rectal temperature daily. If the horse has a fever, meaning a temperature over 101.5F, call the veterinarian at 609-291-0535.
  2. Do not board your horse in a paddock with moving water and turn the lights off in the barn at night to reduce consumption of infected flies, flatworms, and snails.
  3. Vaccinate your horse. Vaccines for PHF are not very effective, but they are the best prevention available, especially if you are unable to take your horse's temperature every day. The vaccine is ineffective because N. ricketsii is a variable bacteria with many strains. Sometimes the strain in the vaccine may not be the strain that infects your horse making the vaccine less effective.
  4. Move your horse. Although PHF is a life-threatening disease, it is also very regional. In our practice area, we only see cases of PHF between Route 1 and the Delaware River. If your horse lives outside this area, he is unlikely to be in danger.

If yo ur horse is showing signs of PHF, the veterinarian may take both blood and feces for testing. The most common treatments are antibiotics, medication for fever and pain, and supportive care for the feet. If your horse is already severely ill, he may need to go to the hospital for intravenous fluids and laminitis management. PHF is not transmitted directly from horse to horse so it is safe to stall healthy horses next to a sick horse.

If you have questions about vaccination or think your horse may have PHF, please call our office immediately at 609-291-0535 or contact us through our website here .
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Classic mercury medical thermometer and electronic medical thermometer with LCD in the body of blue color on a light background. Isolation.
Red and white horse drinks water from the river. Horses on the river.
macro photography of a syringe ready to put a vaccine