Fever of Unknown Origin Average Cost

From 392 quotes ranging from $650 - 10,000

Average Cost


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What is Fever of Unknown Origin?

A fever that rises above the normal range is known as hyperthermia. In both horses and humans, a fever can be the sign of inflammatory, infectious, or a type of immune-mediated illness. It may also be a symptom of a type of disease. When a patient goes to the doctor, or in this case, a veterinarian, a fever can usually be explained by performing a physical examination and by possibly performing lab work. There are times, however, when the fever simply cannot be explained as to why it is occurring. These rare cases are known as a diagnosis of fever of unknown origin.

Typically, horses that come down with a fever show other signs of being ill, such as resistance to eating, the urge to rest, the inability to exercise, and just a general sense of malaise and lethargy. Fever of unknown origin is a fever in a horse without any other symptoms of being sick.

Fever of unknown origin in horses is characterized by a fever that lasts for many days to weeks, that is not coupled with any other specific condition.

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Symptoms of Fever of Unknown Origin in Horses

When first noticing this illness, there will be no other symptoms other than an elevated body temperature of your horse. Symptoms may include:

  • Elevated body temperature
  • Prolonged fever with no other symptoms


There are specific types of inflammatory processes that may be related to fever of unknown origin, and once testing is complete, may lead the veterinarian to the diagnosis. Types of inflammatory processes that may play a role in fever of unknown origin may include:

  • Abscesses (lungs, peritoneum, pleura)
  • Endocarditis
  • Polyarthritis
  • Pyelonephritis
  • Septic metritis

Causes of Fever of Unknown Origin in Horses

There are several factors which may cause a rise in your horse’s body temperature. Causes of fever of unknown origin may include:

  • Infection
  • Neoplasia
  • Immune-mediated disease or illness
  • Other diseases
  • Unknown or undetermined

Diagnosis of Fever of Unknown Origin in Horses

If your horse has had a fever for a prolonged period of time, contact your veterinarian. Your veterinarian will give your horse a complete examination and ask questions about your horse’s symptoms and how long the symptoms have been present. He will perform a thorough review of the horse’s history, such as his vaccination records, parasite controls in place, and his history of traveling. If there are no other symptoms, the veterinarian will need to perform several different types of tests to figure out where the fever is originating from.

He will begin with a complete blood count, biochemistry profile, and urinary testing. The first stage of testing includes these tests in addition to ophthalmic testing, a neurological test, a serum profile, and fibrinogen testing. The veterinarian will take a look at these results, and if nothing is found, will continue on to another batch of testing. 

He may take blood cultures, and then test the following: arthrocentesis, lymph node and other organ aspiration, body fluids, rectal cytology, serology, and fecal cultures. He may also perform an echocardiogram and abdominal ultrasound, and perform x-rays on your horse’s bones and joints. Furthermore, he may perform molecular diagnostic testing. Once he takes a look at the results, he may come to a semi-conclusion of fever of unknown origin; however, more tests will need to be performed for a definite diagnosis. 

Diagnostic testing can be quite expensive if your horse has an unexplained, prolonged fever, as there is a great number of tests that will need to be performed to attempt to find the origin. The reason behind all of the laboratory testing is to completely understand the horse’s body and systems in order to find any illness that may be causing the fever.

Treatment of Fever of Unknown Origin in Horses

After every type of test has been conducted, your veterinarian may not come up with a specific diagnosis to your horse’s fever. In this case, he will need to treat your horse for his fever without having an actual cause of the rise in his temperature. Treatment methods can include:


NSAIDS can help your horse if he is uncomfortable from the fever, and can help bring the fever down to somewhat normal. These medications should only be given if your horse’s temperature gets so high that he is genuinely suffering from discomfort. 

IV Therapy

IV therapy can be very beneficial, as it will keep the horse hydrated and keep his electrolyte levels up. Over time, a high fever can lead to dehydration and the unwillingness to eat, and veterinarians recommend keeping plenty of fluids in his system.

Trial Therapy

Your veterinarian may or may not mention trial therapy with your horse. Many opt to not recommend this type of therapy, as this type of blind therapy can harm the horse. Giving a broad spectrum antibiotic or antimicrobial medication may seem beneficial; however, it can cause toxicity due to an overdose of drugs or a bacterial resistant infection.

Recovery of Fever of Unknown Origin in Horses

Recovery and management of fever of unknown origin and horses is completely dependent upon the reasoning behind your horse’s fever. The mystery of this condition is the fact that the veterinarian is not able to find the cause of the fever. In this case, in terms of recovery, it will depend upon your horse’s condition.

Your veterinarian will give you instructions on how to properly monitor your horse. You will need to take your horse’s temperature regularly to see if by chance the fever is subsiding. Although the veterinarian performed a multitude of testing that may have found no results, it will still be important to watch your horse for any new symptoms or behavioral changes. If you see any new symptoms develop, be sure to contact your veterinarian for repeated tests or further observation.

Quarter Horse
20 Years
Has Symptoms
First noticed my horse had a fever when went in for her morning feeding but she was standing in the corner of her stall and wouldn't walk. Checked her temp. It was 104. Called the vet. That was 13 days ago. During this time the vet checked her lungs, abdomen, heart, uterus (she was in the middle of a very strong estrous), hooves. Couldn't find anything. Took her blood and found that she had a very elevated white blood count. Put her on uniprim and bute. I iced her feet a couple of times a day. The next couple of days her fever went down. Finished the 7 days of uniprim. The 8th day her fever came back. This time 102. Vet decided to give her another round of uniprim and continue her bute. Her feet are still very sore. Farrier came out and made sure her feet were trimmed properly. He thought she was foundering and that that was the cause of the fever. Continued to check fever and give the uniprim and Bute. Fever stayed at 102. Now , today, the fever has climbed to 103.4. Same condition. No signs of any infection but she is still limping and shifting weight from side to side. Vet has recommended that she stay in stall and not free roaming in pasture so as to not cause damage to hooves. I don't know what to do! Ive already spent over 600 dollars with no improvement.