Understanding Fever of Unknown Origin in Dogs

Fever of unknown origin in dogs is a serious condition that can be caused by a wide range of underlying issues, including infections, inflammatory diseases, and even cancer.

It's estimated that up to 20% of dogs with fever will have an unknown cause, making it a challenging diagnosis for veterinarians.

Dogs with fever of unknown origin may exhibit symptoms such as loss of appetite, lethargy, and vomiting, which can be vague and non-specific, making it difficult to pinpoint the underlying cause.

In some cases, the fever may be caused by a bacterial infection, such as Lyme disease or Ehrlichiosis, which can be diagnosed with a simple blood test.

Related reading: What Food Gives Dogs Diarrhea

Fever of unknown origin, or FUO, is a common syndrome in dogs that affects their overall health.

Affected dogs experience an elevated body temperature, usually accompanied by lethargy, weakness, and a lack of appetite.

In most cases, the cause of FUO is not determined, which is why it's called a syndrome of unknown origin.

Most pets with FUO are treated for bacterial infections, and fortunately, this treatment is usually successful.

Dogs with FUO often exhibit symptoms that can be concerning for their owners, but with proper treatment, they can recover and return to their normal selves.

A fever of unknown origin in dogs can be a concerning and frustrating experience for pet owners. Elevated body temperature is the most consistent symptom, with pets often having a temperature above 103º F.

Most pets with fever of unknown origin are weak and lethargic due to fever and dehydration. This can be a challenging time for both dogs and their owners.

Lack of appetite is a common symptom of fever of unknown origin in dogs. If your dog is not eating, it's essential to monitor their temperature and watch for other signs.

Pets with fever of unknown origin sometimes tremble, which can be a sign of discomfort or distress.

Here are some common symptoms of a fever in dogs:

These symptoms can be a good indication that your dog needs medical attention. If you notice any of these signs, it's crucial to monitor your dog's temperature and seek veterinary care if necessary.

Dogs with a fever of unknown origin may also exhibit clinical signs such as lethargy, reluctance to move, loss of appetite, increased heart and breathing rates, and dehydration.

Fever of unknown origin in dogs can be a frustrating and worrisome condition for pet owners. The causes of fever of unknown origin are numerous and varied.

Pets that go outdoors, like cats, are at increased risk of infection and therefore fever of unknown origin.

Young animals suffer from fever of unknown origin more often than older animals.

Flea infestation is a risk factor for fever of unknown origin, as fleas can transmit diseases like Mycoplasma and Bartonella that may cause fever.

A fever is initiated by the presence of a pyrogen, which can be produced within the body or from outside the body.

The pyrogen causes the release of substances from white blood cells, such as interleukin-1, interleukin-6, and tumor necrosis factor, which reset the body's thermostat and activate physiologic responses to elevate the temperature.

Determining the cause of a fever of unknown origin in dogs can be difficult, but there are many potential causes, including viral, bacterial, fungal, or parasitic infections, inflammation due to an immune-mediated problem, or a reaction to a drug or vaccination.

You might like: Spotted Rocky Mountain Fever in Dogs

Some common causes of fever in dogs include tooth infection or abscess, bacterial, fungal or viral infection, urinary tract infection, ear infection, infected bite, scratch or cut, and ingestion of poisonous materials.

Here are some potential causes of fever of unknown origin in dogs:

It's essential to provide your veterinarian with any relevant information, such as recent travel, exposure to unknown or infected animals, flea or tick infestation, recent vaccinations, and any supplements or medications your dog may be taking.

Diagnosis of fever of unknown origin in dogs involves a thorough physical examination, including checks for neurological, limb, and eye problems. Initial tests may include blood work, urinalysis, and urine cultures to rule out underlying infections.

A complete blood cell count (CBC) and serum biochemistry panel are typically performed to evaluate the dog's overall health. Urine cultures are also common to check for urinary tract infections.

In some cases, additional tests such as radiographs (X-rays), ultrasound, or blood cultures may be necessary to identify the underlying cause of the fever. These tests can help diagnose infections, inflammatory diseases, or other conditions that may be contributing to the fever.

Explore further: Treat Milk Fever

Diagnosis of fever of unknown origin is made when no cause can be found for a pet's elevated body temperature.

In most cases, veterinarians will start by taking radiographs (X-rays) and performing basic blood and urine tests before starting treatment for the syndrome.

Pets that don't respond to initial treatment may require comprehensive, advanced testing, including diagnostic imaging (ultrasound), cultures for bacteria and fungus, DNA testing for pathogens, and blood tests called titers for exposure to specific pathogenic organisms.

A thorough physical examination is a key part of diagnosing fever of unknown origin, including looking for problems with the neurological system, limbs and joints, and eyes.

Diagnostic blood tests usually include a complete blood cell count (CBC), a serum biochemistry panel, and a urinalysis.

Urine cultures are often performed to search for an underlying urinary tract infection.

Initial laboratory tests also include chest and abdomen X-rays.

For further diagnostic efforts, some initial tests may need to be repeated, particularly the physical examination, and more specialized tests may be needed.

Additional tests might include blood tests, specialized tests for infectious diseases, ultrasound of the abdomen, chest, or heart, and analysis and bacterial cultures of various body fluids.

Treatment of fever of unknown origin typically takes place in a hospital setting, where intravenous fluids, antibiotics, and pain killers are administered to help manage symptoms such as body aches.

In some cases, anti-inflammatory medications like prednisone or NSAIDs may be used, but they must be used cautiously as they can exacerbate some types of infection.

Rarely, the most serious cases require intensive management and supervision in a 24-hour veterinary facility.

Different treatments may be tried without a diagnosis, including antibiotics, antifungal agents, and anti-inflammatory or immunosuppressive therapy.

Careful monitoring is needed when trying different treatments, as they can carry significant risk.

Intravenous fluid therapy or fever-reducing medications can help alleviate symptoms such as loss of appetite, loss of energy, and dehydration.

In most cases, symptoms resolve within 48 hours of starting treatment.

Pets that do not respond to treatment within 48 hours or suffer from recurring episodes of fever may require more extensive treatment and diagnostics.

Consider reading: Service and Therapy Dogs