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What Is the Treatment for Potomac Horse Fever?

Rebecca Harkin
Rebecca Harkin

Potomac horse fever is treated with a course of the antibiotic oxytetracycline. Horses infected with this illness are also frequently given fluid replacement therapy as well as electrolyte replacement therapy when diarrhea is severe. Non-steroid anti-inflammatory drugs may also be administered to manage a painful hoof condition often associated with this sickness. Vaccines against this medical condition are available, but complete immunity is not always achieved with the vaccine.

Treatment of Potomac horse fever is fairly successful if the infection is caught early, so it is important for a groom to be aware of the symptoms. A horse suffering from this infection will typically eat less feed, have a fever, and have either a decrease in waste production or will have diarrhea. Other symptoms may include depression, swelling, and laminitis, a condition where the circulation to the hooves is decreased, causing swelling and lameness. Potomac horse fever may also cause an expecting mare to abort her fetus.

Potomac horse fever is typically treated with oxytetracycline.
Potomac horse fever is typically treated with oxytetracycline.

Once a groom observes any of these symptoms, the veterinarian should be called immediately. A preliminary diagnosis will be made based on symptoms exhibited by the horse and the prevalence of Potomac horse fever in the area. Confirmation of the diagnosis can be done using a real-time polymerase chain reaction to amplify the bacteria’s deoxyribonucleic acid. This test should be performed on both blood and stool samples.

A horse with Potomac horse fever is treated with antibiotics and fluid as well as electrolyte-replacement therapies if diarrhea is severe.
A horse with Potomac horse fever is treated with antibiotics and fluid as well as electrolyte-replacement therapies if diarrhea is severe.

This infection is caused by a fairly virulent bacterium known as Neorickettsia risticii. This bacterium is capable of evading detection by the immune system, so it does not provoke an immune response by the horse’s body. The bacterium accomplishes this feat by hiding inside macrophages, a cellular component of the immune system capable of destroying extrinsic matter, such as bacteria. As a result, the immune system is unable to identify the Neorickettsia risticii as a foreign entity and mount an immune response.

Once symptoms for potomac horse fever are noticed, a veterinarian should be called immediately.
Once symptoms for potomac horse fever are noticed, a veterinarian should be called immediately.

Oxytetracycline is used to treat an infection of Potomac horse fever. This antibiotic is effective because it prevents Neorickettsia risticii from stealthfully hiding inside macrophages. Horses are also usually treated for dehydration with fluid replacement therapy and, when necessary, electrolyte replacement therapy. If the horse is also suffering from laminitis, a non-steroidal anti-inflammatory may be given to manage the animal’s suffering.

Vaccines for Potomac horse fever are not always effective.
Vaccines for Potomac horse fever are not always effective.

A vaccine against Neorickettsia risticii is available. The efficacy of the vaccine, however, is incomplete. Often, vaccinated horses will still get sick and, due to partial immunity, the symptoms may be less noticeable or harder to read. The limited effectiveness of the vaccine may be due to the different strains of this bacterium that have been isolated.

Frequently Asked Questions

What is Potomac Horse Fever and how is it caused?

Potomac Horse Fever (PHF) is a bacterial disease caused by Neorickettsia risticii. It is typically contracted by horses ingesting aquatic insects like caddisflies and mayflies that carry the bacteria, often found near rivers or streams. The disease can lead to symptoms such as fever, diarrhea, and laminitis, and is most commonly seen in late spring, summer, and early fall.

What are the initial signs of Potomac Horse Fever in horses?

Early signs of Potomac Horse Fever include high fever, lethargy, loss of appetite, and mild colic. As the disease progresses, horses may develop severe diarrhea, dehydration, and signs of laminitis. Quick detection and treatment are crucial, as PHF can be fatal if not addressed promptly.

How is Potomac Horse Fever diagnosed in horses?

Diagnosis of Potomac Horse Fever is typically made through a combination of clinical signs and laboratory tests. Veterinarians may use polymerase chain reaction (PCR) tests or antibody tests to detect the presence of Neorickettsia risticii in the horse's blood or feces. Early and accurate diagnosis is vital for effective treatment.

What is the standard treatment for Potomac Horse Fever?

The standard treatment for Potomac Horse Fever involves administering antibiotics such as oxytetracycline, which is effective against the causative bacteria. Supportive care is also crucial, including fluid therapy to combat dehydration and anti-inflammatory medications to address symptoms like fever and laminitis. Early intervention can significantly improve recovery chances.

Can Potomac Horse Fever be prevented?

Prevention of Potomac Horse Fever can be challenging due to its transmission through insect vectors. However, management practices such as turning off stable lights at night to avoid attracting insects and removing standing water can help reduce risk. A vaccine is available, but its efficacy varies, and it may not prevent all cases.

What is the prognosis for a horse diagnosed with Potomac Horse Fever?

The prognosis for a horse with Potomac Horse Fever depends on the severity of the disease and the timeliness of treatment. With prompt antibiotic therapy and supportive care, many horses can recover fully. However, complications like severe laminitis can worsen the prognosis. According to studies, the mortality rate can range from 5% to 30%.

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    • Potomac horse fever is typically treated with oxytetracycline.
      By: Eric Isselée
      Potomac horse fever is typically treated with oxytetracycline.
    • A horse with Potomac horse fever is treated with antibiotics and fluid as well as electrolyte-replacement therapies if diarrhea is severe.
      By: Justin 767
      A horse with Potomac horse fever is treated with antibiotics and fluid as well as electrolyte-replacement therapies if diarrhea is severe.
    • Once symptoms for potomac horse fever are noticed, a veterinarian should be called immediately.
      By: Monkey Business
      Once symptoms for potomac horse fever are noticed, a veterinarian should be called immediately.
    • Vaccines for Potomac horse fever are not always effective.
      By: pholidito
      Vaccines for Potomac horse fever are not always effective.